// Copyright 2020 The Tint Authors.  //
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "src/writer/spirv/builder.h"

#include <iostream>
#include <limits>
#include <sstream>
#include <utility>

#include "spirv/unified1/GLSL.std.450.h"
#include "spirv/unified1/spirv.h"
#include "src/ast/array_accessor_expression.h"
#include "src/ast/assignment_statement.h"
#include "src/ast/binary_expression.h"
#include "src/ast/binding_decoration.h"
#include "src/ast/bitcast_expression.h"
#include "src/ast/block_statement.h"
#include "src/ast/bool_literal.h"
#include "src/ast/builtin_decoration.h"
#include "src/ast/call_expression.h"
#include "src/ast/call_statement.h"
#include "src/ast/case_statement.h"
#include "src/ast/constructor_expression.h"
#include "src/ast/decorated_variable.h"
#include "src/ast/else_statement.h"
#include "src/ast/float_literal.h"
#include "src/ast/identifier_expression.h"
#include "src/ast/if_statement.h"
#include "src/ast/intrinsic.h"
#include "src/ast/location_decoration.h"
#include "src/ast/loop_statement.h"
#include "src/ast/member_accessor_expression.h"
#include "src/ast/null_literal.h"
#include "src/ast/return_statement.h"
#include "src/ast/scalar_constructor_expression.h"
#include "src/ast/set_decoration.h"
#include "src/ast/sint_literal.h"
#include "src/ast/struct.h"
#include "src/ast/struct_member.h"
#include "src/ast/struct_member_offset_decoration.h"
#include "src/ast/switch_statement.h"
#include "src/ast/type/access_control_type.h"
#include "src/ast/type/array_type.h"
#include "src/ast/type/depth_texture_type.h"
#include "src/ast/type/f32_type.h"
#include "src/ast/type/i32_type.h"
#include "src/ast/type/matrix_type.h"
#include "src/ast/type/multisampled_texture_type.h"
#include "src/ast/type/pointer_type.h"
#include "src/ast/type/sampled_texture_type.h"
#include "src/ast/type/storage_texture_type.h"
#include "src/ast/type/struct_type.h"
#include "src/ast/type/texture_type.h"
#include "src/ast/type/u32_type.h"
#include "src/ast/type/vector_type.h"
#include "src/ast/type/void_type.h"
#include "src/ast/type_constructor_expression.h"
#include "src/ast/uint_literal.h"
#include "src/ast/unary_op_expression.h"
#include "src/ast/variable_decl_statement.h"

namespace tint {
namespace writer {
namespace spirv {
namespace {

const char kGLSLstd450[] = "GLSL.std.450";

uint32_t size_of(const InstructionList& instructions) {
  uint32_t size = 0;
  for (const auto& inst : instructions)
    size += inst.word_length();

  return size;
}

uint32_t pipeline_stage_to_execution_model(ast::PipelineStage stage) {
  SpvExecutionModel model = SpvExecutionModelVertex;

  switch (stage) {
    case ast::PipelineStage::kFragment:
      model = SpvExecutionModelFragment;
      break;
    case ast::PipelineStage::kVertex:
      model = SpvExecutionModelVertex;
      break;
    case ast::PipelineStage::kCompute:
      model = SpvExecutionModelGLCompute;
      break;
    case ast::PipelineStage::kNone:
      model = SpvExecutionModelMax;
      break;
  }
  return model;
}

bool LastIsFallthrough(const ast::BlockStatement* stmts) {
  return !stmts->empty() && stmts->last()->IsFallthrough();
}

// A terminator is anything which will case a SPIR-V terminator to be emitted.
// This means things like breaks, fallthroughs and continues which all emit an
// OpBranch or return for the OpReturn emission.
bool LastIsTerminator(const ast::BlockStatement* stmts) {
  if (stmts->empty()) {
    return false;
  }

  auto* last = stmts->last();
  return last->IsBreak() || last->IsContinue() || last->IsDiscard() ||
         last->IsReturn() || last->IsFallthrough();
}

uint32_t IndexFromName(char name) {
  switch (name) {
    case 'x':
    case 'r':
      return 0;
    case 'y':
    case 'g':
      return 1;
    case 'z':
    case 'b':
      return 2;
    case 'w':
    case 'a':
      return 3;
  }
  return std::numeric_limits<uint32_t>::max();
}

/// Returns the matrix type that is |type| or that is wrapped by
/// one or more levels of an arrays inside of |type|.
/// @param type the given type, which must not be null
/// @returns the nested matrix type, or nullptr if none
ast::type::MatrixType* GetNestedMatrixType(ast::type::Type* type) {
  while (type->IsArray()) {
    type = type->AsArray()->type();
  }
  return type->IsMatrix() ? type->AsMatrix() : nullptr;
}

uint32_t intrinsic_to_glsl_method(ast::type::Type* type,
                                  ast::Intrinsic intrinsic) {
  switch (intrinsic) {
    case ast::Intrinsic::kAbs:
      if (type->is_float_scalar_or_vector()) {
        return GLSLstd450FAbs;
      } else {
        return GLSLstd450SAbs;
      }
    case ast::Intrinsic::kAcos:
      return GLSLstd450Acos;
    case ast::Intrinsic::kAsin:
      return GLSLstd450Asin;
    case ast::Intrinsic::kAtan:
      return GLSLstd450Atan;
    case ast::Intrinsic::kAtan2:
      return GLSLstd450Atan2;
    case ast::Intrinsic::kCeil:
      return GLSLstd450Ceil;
    case ast::Intrinsic::kClamp:
      if (type->is_float_scalar_or_vector()) {
        return GLSLstd450NClamp;
      } else if (type->is_unsigned_scalar_or_vector()) {
        return GLSLstd450UClamp;
      } else {
        return GLSLstd450SClamp;
      }
    case ast::Intrinsic::kCos:
      return GLSLstd450Cos;
    case ast::Intrinsic::kCosh:
      return GLSLstd450Cosh;
    case ast::Intrinsic::kCross:
      return GLSLstd450Cross;
    case ast::Intrinsic::kDeterminant:
      return GLSLstd450Determinant;
    case ast::Intrinsic::kDistance:
      return GLSLstd450Distance;
    case ast::Intrinsic::kExp:
      return GLSLstd450Exp;
    case ast::Intrinsic::kExp2:
      return GLSLstd450Exp2;
    case ast::Intrinsic::kFaceForward:
      return GLSLstd450FaceForward;
    case ast::Intrinsic::kFloor:
      return GLSLstd450Floor;
    case ast::Intrinsic::kFma:
      return GLSLstd450Fma;
    case ast::Intrinsic::kFract:
      return GLSLstd450Fract;
    case ast::Intrinsic::kFrexp:
      return GLSLstd450Frexp;
    case ast::Intrinsic::kInverseSqrt:
      return GLSLstd450InverseSqrt;
    case ast::Intrinsic::kLdexp:
      return GLSLstd450Ldexp;
    case ast::Intrinsic::kLength:
      return GLSLstd450Length;
    case ast::Intrinsic::kLog:
      return GLSLstd450Log;
    case ast::Intrinsic::kLog2:
      return GLSLstd450Log2;
    case ast::Intrinsic::kMax:
      if (type->is_float_scalar_or_vector()) {
        return GLSLstd450NMax;
      } else if (type->is_unsigned_scalar_or_vector()) {
        return GLSLstd450UMax;
      } else {
        return GLSLstd450SMax;
      }
    case ast::Intrinsic::kMin:
      if (type->is_float_scalar_or_vector()) {
        return GLSLstd450NMin;
      } else if (type->is_unsigned_scalar_or_vector()) {
        return GLSLstd450UMin;
      } else {
        return GLSLstd450SMin;
      }
    case ast::Intrinsic::kMix:
      return GLSLstd450FMix;
    case ast::Intrinsic::kModf:
      return GLSLstd450Modf;
    case ast::Intrinsic::kNormalize:
      return GLSLstd450Normalize;
    case ast::Intrinsic::kPow:
      return GLSLstd450Pow;
    case ast::Intrinsic::kReflect:
      return GLSLstd450Reflect;
    case ast::Intrinsic::kRound:
      return GLSLstd450Round;
    case ast::Intrinsic::kSign:
      return GLSLstd450FSign;
    case ast::Intrinsic::kSin:
      return GLSLstd450Sin;
    case ast::Intrinsic::kSinh:
      return GLSLstd450Sinh;
    case ast::Intrinsic::kSmoothStep:
      return GLSLstd450SmoothStep;
    case ast::Intrinsic::kSqrt:
      return GLSLstd450Sqrt;
    case ast::Intrinsic::kStep:
      return GLSLstd450Step;
    case ast::Intrinsic::kTan:
      return GLSLstd450Tan;
    case ast::Intrinsic::kTanh:
      return GLSLstd450Tanh;
    case ast::Intrinsic::kTrunc:
      return GLSLstd450Trunc;
    default:
      break;
  }
  return 0;
}

}  // namespace

Builder::AccessorInfo::AccessorInfo() : source_id(0), source_type(nullptr) {}

Builder::AccessorInfo::~AccessorInfo() {}

Builder::Builder(Context* ctx, ast::Module* mod)
    : ctx_(ctx), mod_(mod), scope_stack_({}) {
  assert(ctx_);
}

Builder::~Builder() = default;

bool Builder::Build() {
  push_capability(SpvCapabilityShader);

  push_memory_model(spv::Op::OpMemoryModel,
                    {Operand::Int(SpvAddressingModelLogical),
                     Operand::Int(SpvMemoryModelGLSL450)});

  for (auto* var : mod_->global_variables()) {
    if (!GenerateGlobalVariable(var)) {
      return false;
    }
  }

  for (auto* func : mod_->functions()) {
    if (!GenerateFunction(func)) {
      return false;
    }
  }

  return true;
}

Operand Builder::result_op() {
  return Operand::Int(next_id());
}

uint32_t Builder::total_size() const {
  // The 5 covers the magic, version, generator, id bound and reserved.
  uint32_t size = 5;

  size += size_of(capabilities_);
  size += size_of(extensions_);
  size += size_of(ext_imports_);
  size += size_of(memory_model_);
  size += size_of(entry_points_);
  size += size_of(execution_modes_);
  size += size_of(debug_);
  size += size_of(annotations_);
  size += size_of(types_);
  for (const auto& func : functions_) {
    size += func.word_length();
  }

  return size;
}

void Builder::iterate(std::function<void(const Instruction&)> cb) const {
  for (const auto& inst : capabilities_) {
    cb(inst);
  }
  for (const auto& inst : extensions_) {
    cb(inst);
  }
  for (const auto& inst : ext_imports_) {
    cb(inst);
  }
  for (const auto& inst : memory_model_) {
    cb(inst);
  }
  for (const auto& inst : entry_points_) {
    cb(inst);
  }
  for (const auto& inst : execution_modes_) {
    cb(inst);
  }
  for (const auto& inst : debug_) {
    cb(inst);
  }
  for (const auto& inst : annotations_) {
    cb(inst);
  }
  for (const auto& inst : types_) {
    cb(inst);
  }
  for (const auto& func : functions_) {
    func.iterate(cb);
  }
}

void Builder::push_capability(uint32_t cap) {
  capabilities_.push_back(
      Instruction{spv::Op::OpCapability, {Operand::Int(cap)}});
}

void Builder::GenerateLabel(uint32_t id) {
  push_function_inst(spv::Op::OpLabel, {Operand::Int(id)});
  current_label_id_ = id;
}

uint32_t Builder::GenerateU32Literal(uint32_t val) {
  ast::type::U32Type u32;
  ast::SintLiteral lit(&u32, val);
  return GenerateLiteralIfNeeded(nullptr, &lit);
}

bool Builder::GenerateAssignStatement(ast::AssignmentStatement* assign) {
  auto lhs_id = GenerateExpression(assign->lhs());
  if (lhs_id == 0) {
    return false;
  }
  auto rhs_id = GenerateExpression(assign->rhs());
  if (rhs_id == 0) {
    return false;
  }

  // If the thing we're assigning is a pointer then we must load it first.
  rhs_id = GenerateLoadIfNeeded(assign->rhs()->result_type(), rhs_id);

  GenerateStore(lhs_id, rhs_id);
  return true;
}

bool Builder::GenerateBreakStatement(ast::BreakStatement*) {
  if (merge_stack_.empty()) {
    error_ = "Attempted to break without a merge block";
    return false;
  }
  push_function_inst(spv::Op::OpBranch, {Operand::Int(merge_stack_.back())});
  return true;
}

bool Builder::GenerateContinueStatement(ast::ContinueStatement*) {
  if (continue_stack_.empty()) {
    error_ = "Attempted to continue without a continue block";
    return false;
  }
  push_function_inst(spv::Op::OpBranch, {Operand::Int(continue_stack_.back())});
  return true;
}

// TODO(dsinclair): This is generating an OpKill but the semantics of kill
// haven't been defined for WGSL yet. So, this may need to change.
// https://github.com/gpuweb/gpuweb/issues/676
bool Builder::GenerateDiscardStatement(ast::DiscardStatement*) {
  push_function_inst(spv::Op::OpKill, {});
  return true;
}

bool Builder::GenerateEntryPoint(ast::Function* func, uint32_t id) {
  auto stage = pipeline_stage_to_execution_model(func->pipeline_stage());
  if (stage == SpvExecutionModelMax) {
    error_ = "Unknown pipeline stage provided";
    return false;
  }

  // TODO(dsinclair): This should be using the namer to update the entry point
  // name to a non-user provided string. Disable for now until we can update
  // the inspector and land the same change in MSL / HLSL to all roll into Dawn
  // at the same time.
  // OperandList operands = {Operand::Int(stage), Operand::Int(id),
  //                         Operand::String(ctx_.namer()->NameFor(func->name()))};
  OperandList operands = {Operand::Int(stage), Operand::Int(id),
                          Operand::String(func->name())};

  for (const auto* var : func->referenced_module_variables()) {
    // For SPIR-V 1.3 we only output Input/output variables. If we update to
    // SPIR-V 1.4 or later this should be all variables.
    if (var->storage_class() != ast::StorageClass::kInput &&
        var->storage_class() != ast::StorageClass::kOutput) {
      continue;
    }

    uint32_t var_id;
    if (!scope_stack_.get(var->name(), &var_id)) {
      error_ = "unable to find ID for global variable: " + var->name();
      return false;
    }

    operands.push_back(Operand::Int(var_id));
  }
  push_entry_point(spv::Op::OpEntryPoint, operands);

  return true;
}

bool Builder::GenerateExecutionModes(ast::Function* func, uint32_t id) {
  // WGSL fragment shader origin is upper left
  if (func->pipeline_stage() == ast::PipelineStage::kFragment) {
    push_execution_mode(
        spv::Op::OpExecutionMode,
        {Operand::Int(id), Operand::Int(SpvExecutionModeOriginUpperLeft)});
  } else if (func->pipeline_stage() == ast::PipelineStage::kCompute) {
    uint32_t x = 0;
    uint32_t y = 0;
    uint32_t z = 0;
    std::tie(x, y, z) = func->workgroup_size();
    push_execution_mode(
        spv::Op::OpExecutionMode,
        {Operand::Int(id), Operand::Int(SpvExecutionModeLocalSize),
         Operand::Int(x), Operand::Int(y), Operand::Int(z)});
  }

  return true;
}

uint32_t Builder::GenerateExpression(ast::Expression* expr) {
  if (expr->IsArrayAccessor()) {
    return GenerateAccessorExpression(expr->AsArrayAccessor());
  }
  if (expr->IsBinary()) {
    return GenerateBinaryExpression(expr->AsBinary());
  }
  if (expr->IsBitcast()) {
    return GenerateBitcastExpression(expr->AsBitcast());
  }
  if (expr->IsCall()) {
    return GenerateCallExpression(expr->AsCall());
  }
  if (expr->IsConstructor()) {
    return GenerateConstructorExpression(nullptr, expr->AsConstructor(), false);
  }
  if (expr->IsIdentifier()) {
    return GenerateIdentifierExpression(expr->AsIdentifier());
  }
  if (expr->IsMemberAccessor()) {
    return GenerateAccessorExpression(expr->AsMemberAccessor());
  }
  if (expr->IsUnaryOp()) {
    return GenerateUnaryOpExpression(expr->AsUnaryOp());
  }

  error_ = "unknown expression type: " + expr->str();
  return 0;
}

bool Builder::GenerateFunction(ast::Function* func) {
  uint32_t func_type_id = GenerateFunctionTypeIfNeeded(func);
  if (func_type_id == 0) {
    return false;
  }

  auto func_op = result_op();
  auto func_id = func_op.to_i();

  push_debug(spv::Op::OpName,
             {Operand::Int(func_id),
              Operand::String(ctx_->namer()->NameFor(func->name()))});

  auto ret_id = GenerateTypeIfNeeded(func->return_type());
  if (ret_id == 0) {
    return false;
  }

  scope_stack_.push_scope();

  auto definition_inst = Instruction{
      spv::Op::OpFunction,
      {Operand::Int(ret_id), func_op, Operand::Int(SpvFunctionControlMaskNone),
       Operand::Int(func_type_id)}};

  InstructionList params;
  for (auto* param : func->params()) {
    auto param_op = result_op();
    auto param_id = param_op.to_i();

    auto param_type_id = GenerateTypeIfNeeded(param->type());
    if (param_type_id == 0) {
      return false;
    }

    push_debug(spv::Op::OpName,
               {Operand::Int(param_id),
                Operand::String(ctx_->namer()->NameFor(param->name()))});
    params.push_back(Instruction{spv::Op::OpFunctionParameter,
                                 {Operand::Int(param_type_id), param_op}});

    scope_stack_.set(param->name(), param_id);
  }

  push_function(Function{definition_inst, result_op(), std::move(params)});

  for (auto* stmt : *func->body()) {
    if (!GenerateStatement(stmt)) {
      return false;
    }
  }

  if (func->IsEntryPoint()) {
    if (!GenerateEntryPoint(func, func_id)) {
      return false;
    }
    if (!GenerateExecutionModes(func, func_id)) {
      return false;
    }
  }

  scope_stack_.pop_scope();

  func_name_to_id_[func->name()] = func_id;
  func_name_to_func_[func->name()] = func;

  return true;
}

uint32_t Builder::GenerateFunctionTypeIfNeeded(ast::Function* func) {
  auto val = type_name_to_id_.find(func->type_name());
  if (val != type_name_to_id_.end()) {
    return val->second;
  }

  auto func_op = result_op();
  auto func_type_id = func_op.to_i();

  auto ret_id = GenerateTypeIfNeeded(func->return_type());
  if (ret_id == 0) {
    return 0;
  }

  OperandList ops = {func_op, Operand::Int(ret_id)};
  for (auto* param : func->params()) {
    auto param_type_id = GenerateTypeIfNeeded(param->type());
    if (param_type_id == 0) {
      return 0;
    }
    ops.push_back(Operand::Int(param_type_id));
  }

  push_type(spv::Op::OpTypeFunction, std::move(ops));

  type_name_to_id_[func->type_name()] = func_type_id;
  return func_type_id;
}

bool Builder::GenerateFunctionVariable(ast::Variable* var) {
  uint32_t init_id = 0;
  if (var->has_constructor()) {
    init_id = GenerateExpression(var->constructor());
    if (init_id == 0) {
      return false;
    }
    init_id = GenerateLoadIfNeeded(var->constructor()->result_type(), init_id);
  }

  if (var->is_const()) {
    if (!var->has_constructor()) {
      error_ = "missing constructor for constant";
      return false;
    }
    scope_stack_.set(var->name(), init_id);
    spirv_id_to_variable_[init_id] = var;
    return true;
  }

  auto result = result_op();
  auto var_id = result.to_i();
  auto sc = ast::StorageClass::kFunction;
  ast::type::PointerType pt(var->type(), sc);
  auto type_id = GenerateTypeIfNeeded(&pt);
  if (type_id == 0) {
    return false;
  }

  push_debug(spv::Op::OpName,
             {Operand::Int(var_id),
              Operand::String(ctx_->namer()->NameFor(var->name()))});

  // TODO(dsinclair) We could detect if the constructor is fully const and emit
  // an initializer value for the variable instead of doing the OpLoad.
  ast::NullLiteral nl(var->type()->UnwrapPtrIfNeeded());
  auto null_id = GenerateLiteralIfNeeded(var, &nl);
  if (null_id == 0) {
    return 0;
  }
  push_function_var({Operand::Int(type_id), result,
                     Operand::Int(ConvertStorageClass(sc)),
                     Operand::Int(null_id)});

  if (var->has_constructor()) {
    GenerateStore(var_id, init_id);
  }

  scope_stack_.set(var->name(), var_id);
  spirv_id_to_variable_[var_id] = var;

  return true;
}

void Builder::GenerateStore(uint32_t to, uint32_t from) {
  push_function_inst(spv::Op::OpStore, {Operand::Int(to), Operand::Int(from)});
}

bool Builder::GenerateGlobalVariable(ast::Variable* var) {
  uint32_t init_id = 0;
  if (var->has_constructor()) {
    if (!var->constructor()->IsConstructor()) {
      error_ = "scalar constructor expected";
      return false;
    }

    init_id = GenerateConstructorExpression(
        var, var->constructor()->AsConstructor(), true);
    if (init_id == 0) {
      return false;
    }
  }

  if (var->is_const()) {
    if (!var->has_constructor()) {
      error_ = "missing constructor for constant";
      return false;
    }
    push_debug(spv::Op::OpName,
               {Operand::Int(init_id),
                Operand::String(ctx_->namer()->NameFor(var->name()))});

    scope_stack_.set_global(var->name(), init_id);
    spirv_id_to_variable_[init_id] = var;
    return true;
  }

  auto result = result_op();
  auto var_id = result.to_i();

  auto sc = var->storage_class() == ast::StorageClass::kNone
                ? ast::StorageClass::kPrivate
                : var->storage_class();

  ast::type::PointerType pt(var->type(), sc);
  auto type_id = GenerateTypeIfNeeded(&pt);
  if (type_id == 0) {
    return false;
  }

  push_debug(spv::Op::OpName,
             {Operand::Int(var_id),
              Operand::String(ctx_->namer()->NameFor(var->name()))});

  auto* type = var->type()->UnwrapAll();

  OperandList ops = {Operand::Int(type_id), result,
                     Operand::Int(ConvertStorageClass(sc))};
  if (var->has_constructor()) {
    ops.push_back(Operand::Int(init_id));
  } else if (!type->IsTexture() && !type->IsSampler()) {
    // Certain cases require us to generate a constructor value.
    //
    // 1- ConstantId's must be attached to the OpConstant, if we have a
    //    variable with a constant_id that doesn't have a constructor we make
    //    one
    // 2- If we don't have a constructor and we're an Output or Private variable
    //    then WGSL requires an initializer.
    if (var->IsDecorated() && var->AsDecorated()->HasConstantIdDecoration()) {
      if (type->IsF32()) {
        ast::FloatLiteral l(type, 0.0f);
        init_id = GenerateLiteralIfNeeded(var, &l);
      } else if (type->IsU32()) {
        ast::UintLiteral l(type, 0);
        init_id = GenerateLiteralIfNeeded(var, &l);
      } else if (type->IsI32()) {
        ast::SintLiteral l(type, 0);
        init_id = GenerateLiteralIfNeeded(var, &l);
      } else if (type->IsBool()) {
        ast::BoolLiteral l(type, false);
        init_id = GenerateLiteralIfNeeded(var, &l);
      } else {
        error_ = "invalid type for constant_id, must be scalar";
        return false;
      }
      if (init_id == 0) {
        return 0;
      }
      ops.push_back(Operand::Int(init_id));
    } else if (var->storage_class() == ast::StorageClass::kPrivate ||
               var->storage_class() == ast::StorageClass::kNone ||
               var->storage_class() == ast::StorageClass::kOutput) {
      ast::NullLiteral nl(type);
      init_id = GenerateLiteralIfNeeded(var, &nl);
      if (init_id == 0) {
        return 0;
      }
      ops.push_back(Operand::Int(init_id));
    }
  }

  push_type(spv::Op::OpVariable, std::move(ops));

  if (var->IsDecorated()) {
    for (auto* deco : var->AsDecorated()->decorations()) {
      if (deco->IsBuiltin()) {
        push_annot(spv::Op::OpDecorate,
                   {Operand::Int(var_id), Operand::Int(SpvDecorationBuiltIn),
                    Operand::Int(ConvertBuiltin(deco->AsBuiltin()->value()))});
      } else if (deco->IsLocation()) {
        push_annot(spv::Op::OpDecorate,
                   {Operand::Int(var_id), Operand::Int(SpvDecorationLocation),
                    Operand::Int(deco->AsLocation()->value())});
      } else if (deco->IsBinding()) {
        push_annot(spv::Op::OpDecorate,
                   {Operand::Int(var_id), Operand::Int(SpvDecorationBinding),
                    Operand::Int(deco->AsBinding()->value())});
      } else if (deco->IsSet()) {
        push_annot(
            spv::Op::OpDecorate,
            {Operand::Int(var_id), Operand::Int(SpvDecorationDescriptorSet),
             Operand::Int(deco->AsSet()->value())});
      } else if (deco->IsConstantId()) {
        // Spec constants are handled elsewhere
      } else {
        error_ = "unknown decoration";
        return false;
      }
    }
  }
  scope_stack_.set_global(var->name(), var_id);
  spirv_id_to_variable_[var_id] = var;
  return true;
}

bool Builder::GenerateArrayAccessor(ast::ArrayAccessorExpression* expr,
                                    AccessorInfo* info) {
  auto idx_id = GenerateExpression(expr->idx_expr());
  if (idx_id == 0) {
    return 0;
  }
  idx_id = GenerateLoadIfNeeded(expr->idx_expr()->result_type(), idx_id);

  // If the source is a pointer we access chain into it. We also access chain
  // into an array of non-scalar types.
  if (info->source_type->IsPointer() ||
      (info->source_type->IsArray() &&
       !info->source_type->AsArray()->type()->is_scalar())) {
    info->access_chain_indices.push_back(idx_id);
    info->source_type = expr->result_type();
    return true;
  }

  auto result_type_id = GenerateTypeIfNeeded(expr->result_type());
  if (result_type_id == 0) {
    return false;
  }

  // We don't have a pointer, so we have to extract value from the vector
  auto extract = result_op();
  auto extract_id = extract.to_i();

  push_function_inst(spv::Op::OpVectorExtractDynamic,
                     {Operand::Int(result_type_id), extract,
                      Operand::Int(info->source_id), Operand::Int(idx_id)});

  info->source_id = extract_id;
  info->source_type = expr->result_type();

  return true;
}

bool Builder::GenerateMemberAccessor(ast::MemberAccessorExpression* expr,
                                     AccessorInfo* info) {
  auto* data_type =
      expr->structure()->result_type()->UnwrapPtrIfNeeded()->UnwrapIfNeeded();

  // If the data_type is a structure we're accessing a member, if it's a
  // vector we're accessing a swizzle.
  if (data_type->IsStruct()) {
    if (!info->source_type->IsPointer()) {
      error_ =
          "Attempting to access a struct member on a non-pointer. Something is "
          "wrong";
      return false;
    }

    auto* strct = data_type->AsStruct()->impl();
    auto name = expr->member()->name();

    uint32_t i = 0;
    for (; i < strct->members().size(); ++i) {
      auto* member = strct->members()[i];
      if (member->name() == name) {
        break;
      }
    }

    auto idx_id = GenerateU32Literal(i);
    if (idx_id == 0) {
      return 0;
    }
    info->access_chain_indices.push_back(idx_id);
    info->source_type = expr->result_type();
    return true;
  }

  if (!data_type->IsVector()) {
    error_ = "Member accessor without a struct or vector. Something is wrong";
    return false;
  }

  auto swiz = expr->member()->name();
  // Single element swizzle is either an access chain or a composite extract
  if (swiz.size() == 1) {
    auto val = IndexFromName(swiz[0]);
    if (val == std::numeric_limits<uint32_t>::max()) {
      error_ = "invalid swizzle name: " + swiz;
      return false;
    }

    if (info->source_type->IsPointer()) {
      auto idx_id = GenerateU32Literal(val);
      if (idx_id == 0) {
        return 0;
      }
      info->access_chain_indices.push_back(idx_id);
    } else {
      auto result_type_id = GenerateTypeIfNeeded(expr->result_type());
      if (result_type_id == 0) {
        return 0;
      }

      auto extract = result_op();
      auto extract_id = extract.to_i();
      push_function_inst(spv::Op::OpCompositeExtract,
                         {Operand::Int(result_type_id), extract,
                          Operand::Int(info->source_id), Operand::Int(val)});

      info->source_id = extract_id;
      info->source_type = expr->result_type();
    }
    return true;
  }

  // Store the type away as it may change if we run the access chain
  auto* incoming_type = info->source_type;

  // Multi-item extract is a VectorShuffle. We have to emit any existing access
  // chain data, then load the access chain and shuffle that.
  if (!info->access_chain_indices.empty()) {
    auto result_type_id = GenerateTypeIfNeeded(info->source_type);
    if (result_type_id == 0) {
      return 0;
    }
    auto extract = result_op();
    auto extract_id = extract.to_i();

    OperandList ops = {Operand::Int(result_type_id), extract,
                       Operand::Int(info->source_id)};
    for (auto id : info->access_chain_indices) {
      ops.push_back(Operand::Int(id));
    }

    push_function_inst(spv::Op::OpAccessChain, ops);

    info->source_id = GenerateLoadIfNeeded(expr->result_type(), extract_id);
    info->source_type = expr->result_type()->UnwrapPtrIfNeeded();
    info->access_chain_indices.clear();
  }

  auto result_type_id = GenerateTypeIfNeeded(expr->result_type());
  if (result_type_id == 0) {
    return false;
  }

  auto vec_id = GenerateLoadIfNeeded(incoming_type, info->source_id);

  auto result = result_op();
  auto result_id = result.to_i();

  OperandList ops = {Operand::Int(result_type_id), result, Operand::Int(vec_id),
                     Operand::Int(vec_id)};

  for (uint32_t i = 0; i < swiz.size(); ++i) {
    auto val = IndexFromName(swiz[i]);
    if (val == std::numeric_limits<uint32_t>::max()) {
      error_ = "invalid swizzle name: " + swiz;
      return false;
    }

    ops.push_back(Operand::Int(val));
  }

  push_function_inst(spv::Op::OpVectorShuffle, ops);
  info->source_id = result_id;
  info->source_type = expr->result_type();

  return true;
}

uint32_t Builder::GenerateAccessorExpression(ast::Expression* expr) {
  assert(expr->IsArrayAccessor() || expr->IsMemberAccessor());

  // Gather a list of all the member and array accessors that are in this chain.
  // The list is built in reverse order as that's the order we need to access
  // the chain.
  std::vector<ast::Expression*> accessors;
  ast::Expression* source = expr;
  while (true) {
    if (source->IsArrayAccessor()) {
      accessors.insert(accessors.begin(), source);
      source = source->AsArrayAccessor()->array();
    } else if (source->IsMemberAccessor()) {
      accessors.insert(accessors.begin(), source);
      source = source->AsMemberAccessor()->structure();
    } else {
      break;
    }
  }

  AccessorInfo info;
  info.source_id = GenerateExpression(source);
  if (info.source_id == 0) {
    return 0;
  }
  info.source_type = source->result_type();

  // If our initial access is into an array of non-scalar types, and that array
  // is not a pointer, then we need to load that array into a variable in order
  // to access chain into the array.
  if (accessors[0]->IsArrayAccessor()) {
    auto* ary_res_type =
        accessors[0]->AsArrayAccessor()->array()->result_type();

    if (!ary_res_type->IsPointer() &&
        (ary_res_type->IsArray() &&
         !ary_res_type->AsArray()->type()->is_scalar())) {
      ast::type::PointerType ptr(ary_res_type, ast::StorageClass::kFunction);
      auto result_type_id = GenerateTypeIfNeeded(&ptr);
      if (result_type_id == 0) {
        return 0;
      }

      auto ary_result = result_op();

      ast::NullLiteral nl(ary_res_type);
      auto init = GenerateLiteralIfNeeded(nullptr, &nl);

      // If we're access chaining into an array then we must be in a function
      push_function_var(
          {Operand::Int(result_type_id), ary_result,
           Operand::Int(ConvertStorageClass(ast::StorageClass::kFunction)),
           Operand::Int(init)});

      push_function_inst(spv::Op::OpStore,
                         {ary_result, Operand::Int(info.source_id)});

      info.source_id = ary_result.to_i();
    }
  }

  std::vector<uint32_t> access_chain_indices;
  for (auto* accessor : accessors) {
    if (accessor->IsArrayAccessor()) {
      if (!GenerateArrayAccessor(accessor->AsArrayAccessor(), &info)) {
        return 0;
      }
    } else if (accessor->IsMemberAccessor()) {
      if (!GenerateMemberAccessor(accessor->AsMemberAccessor(), &info)) {
        return 0;
      }

    } else {
      error_ = "invalid accessor in list: " + accessor->str();
      return 0;
    }
  }

  if (!info.access_chain_indices.empty()) {
    auto result_type_id = GenerateTypeIfNeeded(expr->result_type());
    if (result_type_id == 0) {
      return 0;
    }

    auto result = result_op();
    auto result_id = result.to_i();

    OperandList ops = {Operand::Int(result_type_id), result,
                       Operand::Int(info.source_id)};
    for (auto id : info.access_chain_indices) {
      ops.push_back(Operand::Int(id));
    }

    push_function_inst(spv::Op::OpAccessChain, ops);
    info.source_id = result_id;
  }

  return info.source_id;
}

uint32_t Builder::GenerateIdentifierExpression(
    ast::IdentifierExpression* expr) {
  uint32_t val = 0;
  if (scope_stack_.get(expr->name(), &val)) {
    return val;
  }

  error_ = "unable to find variable with identifier: " + expr->name();
  return 0;
}

uint32_t Builder::GenerateLoadIfNeeded(ast::type::Type* type, uint32_t id) {
  if (!type->IsPointer()) {
    return id;
  }

  auto type_id = GenerateTypeIfNeeded(type->UnwrapPtrIfNeeded());
  auto result = result_op();
  auto result_id = result.to_i();
  push_function_inst(spv::Op::OpLoad,
                     {Operand::Int(type_id), result, Operand::Int(id)});
  return result_id;
}

uint32_t Builder::GenerateUnaryOpExpression(ast::UnaryOpExpression* expr) {
  auto result = result_op();
  auto result_id = result.to_i();

  auto val_id = GenerateExpression(expr->expr());
  if (val_id == 0) {
    return 0;
  }
  val_id = GenerateLoadIfNeeded(expr->expr()->result_type(), val_id);

  auto type_id = GenerateTypeIfNeeded(expr->result_type());
  if (type_id == 0) {
    return 0;
  }

  spv::Op op = spv::Op::OpNop;
  if (expr->op() == ast::UnaryOp::kNegation) {
    if (expr->result_type()->is_float_scalar_or_vector()) {
      op = spv::Op::OpFNegate;
    } else {
      op = spv::Op::OpSNegate;
    }
  } else if (expr->op() == ast::UnaryOp::kNot) {
    op = spv::Op::OpLogicalNot;
  }
  if (op == spv::Op::OpNop) {
    error_ = "invalid unary op type";
    return 0;
  }

  push_function_inst(op, {Operand::Int(type_id), result, Operand::Int(val_id)});

  return result_id;
}

void Builder::GenerateGLSLstd450Import() {
  if (import_name_to_id_.find(kGLSLstd450) != import_name_to_id_.end()) {
    return;
  }

  auto result = result_op();
  auto id = result.to_i();

  push_ext_import(spv::Op::OpExtInstImport,
                  {result, Operand::String(kGLSLstd450)});

  import_name_to_id_[kGLSLstd450] = id;
}

uint32_t Builder::GenerateConstructorExpression(
    ast::Variable* var,
    ast::ConstructorExpression* expr,
    bool is_global_init) {
  if (expr->IsScalarConstructor()) {
    return GenerateLiteralIfNeeded(var, expr->AsScalarConstructor()->literal());
  }
  if (expr->IsTypeConstructor()) {
    return GenerateTypeConstructorExpression(expr->AsTypeConstructor(),
                                             is_global_init);
  }

  error_ = "unknown constructor expression";
  return 0;
}

bool Builder::is_constructor_const(ast::Expression* expr, bool is_global_init) {
  if (!expr->IsConstructor()) {
    return false;
  }
  if (expr->AsConstructor()->IsScalarConstructor()) {
    return true;
  }

  auto* tc = expr->AsConstructor()->AsTypeConstructor();
  auto* result_type = tc->type()->UnwrapAll();
  for (size_t i = 0; i < tc->values().size(); ++i) {
    auto* e = tc->values()[i];

    if (!e->IsConstructor()) {
      if (is_global_init) {
        error_ = "constructor must be a constant expression";
        return false;
      }
      return false;
    }
    if (!is_constructor_const(e, is_global_init)) {
      return false;
    }
    if (has_error()) {
      return false;
    }

    if (result_type->IsVector() && !e->AsConstructor()->IsScalarConstructor()) {
      return false;
    }

    // This should all be handled by |is_constructor_const| call above
    if (!e->AsConstructor()->IsScalarConstructor()) {
      continue;
    }

    auto* sc = e->AsConstructor()->AsScalarConstructor();
    ast::type::Type* subtype = result_type->UnwrapAll();
    if (subtype->IsVector()) {
      subtype = subtype->AsVector()->type()->UnwrapAll();
    } else if (subtype->IsMatrix()) {
      subtype = subtype->AsMatrix()->type()->UnwrapAll();
    } else if (subtype->IsArray()) {
      subtype = subtype->AsArray()->type()->UnwrapAll();
    } else if (subtype->IsStruct()) {
      subtype = subtype->AsStruct()->impl()->members()[i]->type()->UnwrapAll();
    }
    if (subtype != sc->result_type()->UnwrapAll()) {
      return false;
    }
  }
  return true;
}

uint32_t Builder::GenerateTypeConstructorExpression(
    ast::TypeConstructorExpression* init,
    bool is_global_init) {
  auto& values = init->values();

  // Generate the zero initializer if there are no values provided.
  if (values.empty()) {
    ast::NullLiteral nl(init->type()->UnwrapPtrIfNeeded());
    return GenerateLiteralIfNeeded(nullptr, &nl);
  }

  std::ostringstream out;
  out << "__const";

  auto* result_type = init->type()->UnwrapAll();
  bool constructor_is_const = is_constructor_const(init, is_global_init);
  if (has_error()) {
    return 0;
  }

  bool can_cast_or_copy = result_type->is_scalar();

  if (result_type->IsVector() && result_type->AsVector()->type()->is_scalar()) {
    auto* value_type = values[0]->result_type()->UnwrapAll();
    can_cast_or_copy =
        (value_type->IsVector() &&
         value_type->AsVector()->type()->is_scalar() &&
         result_type->AsVector()->size() == value_type->AsVector()->size());
  }
  if (can_cast_or_copy) {
    return GenerateCastOrCopyOrPassthrough(result_type, values[0]);
  }

  auto type_id = GenerateTypeIfNeeded(init->type());
  if (type_id == 0) {
    return 0;
  }

  bool result_is_constant_composite = constructor_is_const;
  bool result_is_spec_composite = false;

  if (result_type->IsVector()) {
    result_type = result_type->AsVector()->type();
  }

  OperandList ops;
  for (auto* e : values) {
    uint32_t id = 0;
    if (constructor_is_const) {
      id = GenerateConstructorExpression(nullptr, e->AsConstructor(),
                                         is_global_init);
    } else {
      id = GenerateExpression(e);
      id = GenerateLoadIfNeeded(e->result_type(), id);
    }
    if (id == 0) {
      return 0;
    }

    auto* value_type = e->result_type()->UnwrapPtrIfNeeded();
    // If the result and value types are the same we can just use the object.
    // If the result is not a vector then we should have validated that the
    // value type is a correctly sized vector so we can just use it directly.
    if (result_type == value_type || result_type->IsMatrix() ||
        result_type->IsArray() || result_type->IsStruct()) {
      out << "_" << id;

      ops.push_back(Operand::Int(id));
      continue;
    }

    // Both scalars, but not the same type so we need to generate a conversion
    // of the value.
    if (value_type->is_scalar() && result_type->is_scalar()) {
      id = GenerateCastOrCopyOrPassthrough(result_type, values[0]);
      out << "_" << id;
      ops.push_back(Operand::Int(id));
      continue;
    }

    // When handling vectors as the values there a few cases to take into
    // consideration:
    //  1. Module scoped vec3<f32>(vec2<f32>(1, 2), 3)  -> OpSpecConstantOp
    //  2. Function scoped vec3<f32>(vec2<f32>(1, 2), 3) ->  OpCompositeExtract
    //  3. Either array<vec3<f32>, 1>(vec3<f32>(1, 2, 3))  -> use the ID.
    //       -> handled above
    //
    // For cases 1 and 2, if the type is different we also may need to insert
    // a type cast.
    if (value_type->IsVector()) {
      auto* vec = value_type->AsVector();
      auto* vec_type = vec->type();

      auto value_type_id = GenerateTypeIfNeeded(vec_type);
      if (value_type_id == 0) {
        return 0;
      }

      for (uint32_t i = 0; i < vec->size(); ++i) {
        auto extract = result_op();
        auto extract_id = extract.to_i();

        if (!is_global_init) {
          // A non-global initializer. Case 2.
          push_function_inst(spv::Op::OpCompositeExtract,
                             {Operand::Int(value_type_id), extract,
                              Operand::Int(id), Operand::Int(i)});

          // We no longer have a constant composite, but have to do a
          // composite construction as these calls are inside a function.
          result_is_constant_composite = false;
        } else {
          // A global initializer, must use OpSpecConstantOp. Case 1.
          auto idx_id = GenerateU32Literal(i);
          if (idx_id == 0) {
            return 0;
          }
          push_type(spv::Op::OpSpecConstantOp,
                    {Operand::Int(value_type_id), extract,
                     Operand::Int(SpvOpCompositeExtract), Operand::Int(id),
                     Operand::Int(idx_id)});

          result_is_spec_composite = true;
        }

        out << "_" << extract_id;
        ops.push_back(Operand::Int(extract_id));
      }
    } else {
      error_ = "Unhandled type cast value type";
      return 0;
    }
  }

  auto str = out.str();
  auto val = const_to_id_.find(str);
  if (val != const_to_id_.end()) {
    return val->second;
  }

  auto result = result_op();
  ops.insert(ops.begin(), result);
  ops.insert(ops.begin(), Operand::Int(type_id));

  const_to_id_[str] = result.to_i();

  if (result_is_spec_composite) {
    push_type(spv::Op::OpSpecConstantComposite, ops);
  } else if (result_is_constant_composite) {
    push_type(spv::Op::OpConstantComposite, ops);
  } else {
    push_function_inst(spv::Op::OpCompositeConstruct, ops);
  }

  return result.to_i();
}

uint32_t Builder::GenerateCastOrCopyOrPassthrough(ast::type::Type* to_type,
                                                  ast::Expression* from_expr) {
  auto result = result_op();
  auto result_id = result.to_i();

  auto result_type_id = GenerateTypeIfNeeded(to_type);
  if (result_type_id == 0) {
    return 0;
  }

  auto val_id = GenerateExpression(from_expr);
  if (val_id == 0) {
    return 0;
  }
  val_id = GenerateLoadIfNeeded(from_expr->result_type(), val_id);

  auto* from_type = from_expr->result_type()->UnwrapPtrIfNeeded();

  spv::Op op = spv::Op::OpNop;
  if ((from_type->IsI32() && to_type->IsF32()) ||
      (from_type->is_signed_integer_vector() && to_type->is_float_vector())) {
    op = spv::Op::OpConvertSToF;
  } else if ((from_type->IsU32() && to_type->IsF32()) ||
             (from_type->is_unsigned_integer_vector() &&
              to_type->is_float_vector())) {
    op = spv::Op::OpConvertUToF;
  } else if ((from_type->IsF32() && to_type->IsI32()) ||
             (from_type->is_float_vector() &&
              to_type->is_signed_integer_vector())) {
    op = spv::Op::OpConvertFToS;
  } else if ((from_type->IsF32() && to_type->IsU32()) ||
             (from_type->is_float_vector() &&
              to_type->is_unsigned_integer_vector())) {
    op = spv::Op::OpConvertFToU;
  } else if ((from_type->IsBool() && to_type->IsBool()) ||
             (from_type->IsU32() && to_type->IsU32()) ||
             (from_type->IsI32() && to_type->IsI32()) ||
             (from_type->IsF32() && to_type->IsF32()) ||
             (from_type->IsVector() && (from_type == to_type))) {
    return val_id;
  } else if ((from_type->IsI32() && to_type->IsU32()) ||
             (from_type->IsU32() && to_type->IsI32()) ||
             (from_type->is_signed_integer_vector() &&
              to_type->is_unsigned_integer_vector()) ||
             (from_type->is_unsigned_integer_vector() &&
              to_type->is_integer_scalar_or_vector())) {
    op = spv::Op::OpBitcast;
  }
  if (op == spv::Op::OpNop) {
    error_ = "unable to determine conversion type for cast, from: " +
             from_type->type_name() + " to: " + to_type->type_name();
    return 0;
  }

  push_function_inst(
      op, {Operand::Int(result_type_id), result, Operand::Int(val_id)});

  return result_id;
}

uint32_t Builder::GenerateLiteralIfNeeded(ast::Variable* var,
                                          ast::Literal* lit) {
  auto type_id = GenerateTypeIfNeeded(lit->type());
  if (type_id == 0) {
    return 0;
  }

  auto name = lit->name();
  bool is_spec_constant = false;
  if (var && var->IsDecorated() &&
      var->AsDecorated()->HasConstantIdDecoration()) {
    name = "__spec" + name;
    is_spec_constant = true;
  }

  auto val = const_to_id_.find(name);
  if (val != const_to_id_.end()) {
    return val->second;
  }

  auto result = result_op();
  auto result_id = result.to_i();

  if (is_spec_constant) {
    push_annot(spv::Op::OpDecorate,
               {Operand::Int(result_id), Operand::Int(SpvDecorationSpecId),
                Operand::Int(var->AsDecorated()->constant_id())});
  }

  if (lit->IsBool()) {
    if (lit->AsBool()->IsTrue()) {
      push_type(is_spec_constant ? spv::Op::OpSpecConstantTrue
                                 : spv::Op::OpConstantTrue,
                {Operand::Int(type_id), result});
    } else {
      push_type(is_spec_constant ? spv::Op::OpSpecConstantFalse
                                 : spv::Op::OpConstantFalse,
                {Operand::Int(type_id), result});
    }
  } else if (lit->IsSint()) {
    push_type(
        is_spec_constant ? spv::Op::OpSpecConstant : spv::Op::OpConstant,
        {Operand::Int(type_id), result, Operand::Int(lit->AsSint()->value())});
  } else if (lit->IsUint()) {
    push_type(
        is_spec_constant ? spv::Op::OpSpecConstant : spv::Op::OpConstant,
        {Operand::Int(type_id), result, Operand::Int(lit->AsUint()->value())});
  } else if (lit->IsFloat()) {
    push_type(is_spec_constant ? spv::Op::OpSpecConstant : spv::Op::OpConstant,
              {Operand::Int(type_id), result,
               Operand::Float(lit->AsFloat()->value())});
  } else if (lit->IsNull()) {
    push_type(spv::Op::OpConstantNull, {Operand::Int(type_id), result});
  } else {
    error_ = "unknown literal type";
    return 0;
  }

  const_to_id_[name] = result_id;
  return result_id;
}

uint32_t Builder::GenerateShortCircuitBinaryExpression(
    ast::BinaryExpression* expr) {
  auto lhs_id = GenerateExpression(expr->lhs());
  if (lhs_id == 0) {
    return false;
  }
  lhs_id = GenerateLoadIfNeeded(expr->lhs()->result_type(), lhs_id);

  // Get the ID of the basic block where control flow will diverge. It's the
  // last basic block generated for the left-hand-side of the operator.
  auto original_label_id = current_label_id_;

  auto type_id = GenerateTypeIfNeeded(expr->result_type());
  if (type_id == 0) {
    return 0;
  }

  auto merge_block = result_op();
  auto merge_block_id = merge_block.to_i();

  auto block = result_op();
  auto block_id = block.to_i();

  auto true_block_id = block_id;
  auto false_block_id = merge_block_id;

  // For a logical or we want to only check the RHS if the LHS is failed.
  if (expr->IsLogicalOr()) {
    std::swap(true_block_id, false_block_id);
  }

  push_function_inst(spv::Op::OpSelectionMerge,
                     {Operand::Int(merge_block_id),
                      Operand::Int(SpvSelectionControlMaskNone)});
  push_function_inst(spv::Op::OpBranchConditional,
                     {Operand::Int(lhs_id), Operand::Int(true_block_id),
                      Operand::Int(false_block_id)});

  // Output block to check the RHS
  GenerateLabel(block_id);
  auto rhs_id = GenerateExpression(expr->rhs());
  if (rhs_id == 0) {
    return 0;
  }
  rhs_id = GenerateLoadIfNeeded(expr->rhs()->result_type(), rhs_id);

  // Get the block ID of the last basic block generated for the right-hand-side
  // expression. That block will be an immediate predecessor to the merge block.
  auto rhs_block_id = current_label_id_;
  push_function_inst(spv::Op::OpBranch, {Operand::Int(merge_block_id)});

  // Output the merge block
  GenerateLabel(merge_block_id);

  auto result = result_op();
  auto result_id = result.to_i();

  push_function_inst(spv::Op::OpPhi,
                     {Operand::Int(type_id), result, Operand::Int(lhs_id),
                      Operand::Int(original_label_id), Operand::Int(rhs_id),
                      Operand::Int(rhs_block_id)});

  return result_id;
}

uint32_t Builder::GenerateBinaryExpression(ast::BinaryExpression* expr) {
  // There is special logic for short circuiting operators.
  if (expr->IsLogicalAnd() || expr->IsLogicalOr()) {
    return GenerateShortCircuitBinaryExpression(expr);
  }

  auto lhs_id = GenerateExpression(expr->lhs());
  if (lhs_id == 0) {
    return 0;
  }
  lhs_id = GenerateLoadIfNeeded(expr->lhs()->result_type(), lhs_id);

  auto rhs_id = GenerateExpression(expr->rhs());
  if (rhs_id == 0) {
    return 0;
  }
  rhs_id = GenerateLoadIfNeeded(expr->rhs()->result_type(), rhs_id);

  auto result = result_op();
  auto result_id = result.to_i();

  auto type_id = GenerateTypeIfNeeded(expr->result_type());
  if (type_id == 0) {
    return 0;
  }

  // Handle int and float and the vectors of those types. Other types
  // should have been rejected by validation.
  auto* lhs_type = expr->lhs()->result_type()->UnwrapPtrIfNeeded();
  auto* rhs_type = expr->rhs()->result_type()->UnwrapPtrIfNeeded();
  bool lhs_is_float_or_vec = lhs_type->is_float_scalar_or_vector();
  bool lhs_is_unsigned = lhs_type->is_unsigned_scalar_or_vector();

  spv::Op op = spv::Op::OpNop;
  if (expr->IsAnd()) {
    op = spv::Op::OpBitwiseAnd;
  } else if (expr->IsAdd()) {
    op = lhs_is_float_or_vec ? spv::Op::OpFAdd : spv::Op::OpIAdd;
  } else if (expr->IsDivide()) {
    if (lhs_is_float_or_vec) {
      op = spv::Op::OpFDiv;
    } else if (lhs_is_unsigned) {
      op = spv::Op::OpUDiv;
    } else {
      op = spv::Op::OpSDiv;
    }
  } else if (expr->IsEqual()) {
    op = lhs_is_float_or_vec ? spv::Op::OpFOrdEqual : spv::Op::OpIEqual;
  } else if (expr->IsGreaterThan()) {
    if (lhs_is_float_or_vec) {
      op = spv::Op::OpFOrdGreaterThan;
    } else if (lhs_is_unsigned) {
      op = spv::Op::OpUGreaterThan;
    } else {
      op = spv::Op::OpSGreaterThan;
    }
  } else if (expr->IsGreaterThanEqual()) {
    if (lhs_is_float_or_vec) {
      op = spv::Op::OpFOrdGreaterThanEqual;
    } else if (lhs_is_unsigned) {
      op = spv::Op::OpUGreaterThanEqual;
    } else {
      op = spv::Op::OpSGreaterThanEqual;
    }
  } else if (expr->IsLessThan()) {
    if (lhs_is_float_or_vec) {
      op = spv::Op::OpFOrdLessThan;
    } else if (lhs_is_unsigned) {
      op = spv::Op::OpULessThan;
    } else {
      op = spv::Op::OpSLessThan;
    }
  } else if (expr->IsLessThanEqual()) {
    if (lhs_is_float_or_vec) {
      op = spv::Op::OpFOrdLessThanEqual;
    } else if (lhs_is_unsigned) {
      op = spv::Op::OpULessThanEqual;
    } else {
      op = spv::Op::OpSLessThanEqual;
    }
  } else if (expr->IsModulo()) {
    if (lhs_is_float_or_vec) {
      op = spv::Op::OpFMod;
    } else if (lhs_is_unsigned) {
      op = spv::Op::OpUMod;
    } else {
      op = spv::Op::OpSMod;
    }
  } else if (expr->IsMultiply()) {
    if (lhs_type->is_integer_scalar_or_vector()) {
      // If the left hand side is an integer then this _has_ to be OpIMul as
      // there there is no other integer multiplication.
      op = spv::Op::OpIMul;
    } else if (lhs_type->is_float_scalar() && rhs_type->is_float_scalar()) {
      // Float scalars multiply with OpFMul
      op = spv::Op::OpFMul;
    } else if (lhs_type->is_float_vector() && rhs_type->is_float_vector()) {
      // Float vectors must be validated to be the same size and then use OpFMul
      op = spv::Op::OpFMul;
    } else if (lhs_type->is_float_scalar() && rhs_type->is_float_vector()) {
      // Scalar * Vector we need to flip lhs and rhs types
      // because OpVectorTimesScalar expects <vector>, <scalar>
      std::swap(lhs_id, rhs_id);
      op = spv::Op::OpVectorTimesScalar;
    } else if (lhs_type->is_float_vector() && rhs_type->is_float_scalar()) {
      // float vector * scalar
      op = spv::Op::OpVectorTimesScalar;
    } else if (lhs_type->is_float_scalar() && rhs_type->is_float_matrix()) {
      // Scalar * Matrix we need to flip lhs and rhs types because
      // OpMatrixTimesScalar expects <matrix>, <scalar>
      std::swap(lhs_id, rhs_id);
      op = spv::Op::OpMatrixTimesScalar;
    } else if (lhs_type->is_float_matrix() && rhs_type->is_float_scalar()) {
      // float matrix * scalar
      op = spv::Op::OpMatrixTimesScalar;
    } else if (lhs_type->is_float_vector() && rhs_type->is_float_matrix()) {
      // float vector * matrix
      op = spv::Op::OpVectorTimesMatrix;
    } else if (lhs_type->is_float_matrix() && rhs_type->is_float_vector()) {
      // float matrix * vector
      op = spv::Op::OpMatrixTimesVector;
    } else if (lhs_type->is_float_matrix() && rhs_type->is_float_matrix()) {
      // float matrix * matrix
      op = spv::Op::OpMatrixTimesMatrix;
    } else {
      return 0;
    }
  } else if (expr->IsNotEqual()) {
    op = lhs_is_float_or_vec ? spv::Op::OpFOrdNotEqual : spv::Op::OpINotEqual;
  } else if (expr->IsOr()) {
    op = spv::Op::OpBitwiseOr;
  } else if (expr->IsShiftLeft()) {
    op = spv::Op::OpShiftLeftLogical;
  } else if (expr->IsShiftRight() && lhs_type->is_signed_scalar_or_vector()) {
    // A shift right with a signed LHS is an arithmetic shift.
    op = spv::Op::OpShiftRightArithmetic;
  } else if (expr->IsShiftRight()) {
    op = spv::Op::OpShiftRightLogical;
  } else if (expr->IsSubtract()) {
    op = lhs_is_float_or_vec ? spv::Op::OpFSub : spv::Op::OpISub;
  } else if (expr->IsXor()) {
    op = spv::Op::OpBitwiseXor;
  } else {
    error_ = "unknown binary expression";
    return 0;
  }

  push_function_inst(op, {Operand::Int(type_id), result, Operand::Int(lhs_id),
                          Operand::Int(rhs_id)});
  return result_id;
}

bool Builder::GenerateBlockStatement(const ast::BlockStatement* stmt) {
  scope_stack_.push_scope();
  for (auto* block_stmt : *stmt) {
    if (!GenerateStatement(block_stmt)) {
      return false;
    }
  }
  scope_stack_.pop_scope();

  return true;
}

uint32_t Builder::GenerateCallExpression(ast::CallExpression* expr) {
  if (!expr->func()->IsIdentifier()) {
    error_ = "invalid function name";
    return 0;
  }

  auto* ident = expr->func()->AsIdentifier();

  if (ident->IsIntrinsic()) {
    return GenerateIntrinsic(ident, expr);
  }

  auto type_id = GenerateTypeIfNeeded(expr->func()->result_type());
  if (type_id == 0) {
    return 0;
  }

  auto result = result_op();
  auto result_id = result.to_i();

  OperandList ops = {Operand::Int(type_id), result};

  auto func_id = func_name_to_id_[ident->name()];
  if (func_id == 0) {
    error_ = "unable to find called function: " + ident->name();
    return 0;
  }
  ops.push_back(Operand::Int(func_id));

  for (auto* param : expr->params()) {
    auto id = GenerateExpression(param);
    if (id == 0) {
      return 0;
    }
    id = GenerateLoadIfNeeded(param->result_type(), id);
    ops.push_back(Operand::Int(id));
  }

  push_function_inst(spv::Op::OpFunctionCall, std::move(ops));

  return result_id;
}

uint32_t Builder::GenerateIntrinsic(ast::IdentifierExpression* ident,
                                    ast::CallExpression* call) {
  auto result = result_op();
  auto result_id = result.to_i();

  auto result_type_id = GenerateTypeIfNeeded(call->result_type());
  if (result_type_id == 0) {
    return 0;
  }

  auto intrinsic = ident->intrinsic();

  if (ast::intrinsic::IsTextureIntrinsic(intrinsic)) {
    GenerateTextureIntrinsic(ident, call, Operand::Int(result_type_id), result);
    return result_id;
  }

  OperandList params = {Operand::Int(result_type_id), result};

  if (ast::intrinsic::IsFineDerivative(intrinsic) ||
      ast::intrinsic::IsCoarseDerivative(intrinsic)) {
    push_capability(SpvCapabilityDerivativeControl);
  }

  spv::Op op = spv::Op::OpNop;
  if (intrinsic == ast::Intrinsic::kAny) {
    op = spv::Op::OpAny;
  } else if (intrinsic == ast::Intrinsic::kAll) {
    op = spv::Op::OpAll;
  } else if (intrinsic == ast::Intrinsic::kArrayLength) {
    if (call->params().empty()) {
      error_ = "missing param for runtime array length";
      return 0;
    } else if (!call->params()[0]->IsMemberAccessor()) {
      if (call->params()[0]->result_type()->IsPointer()) {
        error_ = "pointer accessors not supported yet";
      } else {
        error_ = "invalid accessor for runtime array length";
      }
      return 0;
    }
    auto* accessor = call->params()[0]->AsMemberAccessor();
    auto struct_id = GenerateExpression(accessor->structure());
    if (struct_id == 0) {
      return 0;
    }
    params.push_back(Operand::Int(struct_id));

    auto* type = accessor->structure()->result_type()->UnwrapAll();
    if (!type->IsStruct()) {
      error_ =
          "invalid type (" + type->type_name() + ") for runtime array length";
      return 0;
    }
    // Runtime array must be the last member in the structure
    params.push_back(
        Operand::Int(uint32_t(type->AsStruct()->impl()->members().size() - 1)));

    push_function_inst(spv::Op::OpArrayLength, params);
    return result_id;
  } else if (intrinsic == ast::Intrinsic::kCountOneBits) {
    op = spv::Op::OpBitCount;
  } else if (intrinsic == ast::Intrinsic::kDot) {
    op = spv::Op::OpDot;
  } else if (intrinsic == ast::Intrinsic::kDpdx) {
    op = spv::Op::OpDPdx;
  } else if (intrinsic == ast::Intrinsic::kDpdxCoarse) {
    op = spv::Op::OpDPdxCoarse;
  } else if (intrinsic == ast::Intrinsic::kDpdxFine) {
    op = spv::Op::OpDPdxFine;
  } else if (intrinsic == ast::Intrinsic::kDpdy) {
    op = spv::Op::OpDPdy;
  } else if (intrinsic == ast::Intrinsic::kDpdyCoarse) {
    op = spv::Op::OpDPdyCoarse;
  } else if (intrinsic == ast::Intrinsic::kDpdyFine) {
    op = spv::Op::OpDPdyFine;
  } else if (intrinsic == ast::Intrinsic::kFwidth) {
    op = spv::Op::OpFwidth;
  } else if (intrinsic == ast::Intrinsic::kFwidthCoarse) {
    op = spv::Op::OpFwidthCoarse;
  } else if (intrinsic == ast::Intrinsic::kFwidthFine) {
    op = spv::Op::OpFwidthFine;
  } else if (intrinsic == ast::Intrinsic::kIsInf) {
    op = spv::Op::OpIsInf;
  } else if (intrinsic == ast::Intrinsic::kIsNan) {
    op = spv::Op::OpIsNan;
  } else if (intrinsic == ast::Intrinsic::kOuterProduct) {
    op = spv::Op::OpOuterProduct;
  } else if (intrinsic == ast::Intrinsic::kReverseBits) {
    op = spv::Op::OpBitReverse;
  } else if (intrinsic == ast::Intrinsic::kSelect) {
    op = spv::Op::OpSelect;
  } else {
    GenerateGLSLstd450Import();

    auto set_iter = import_name_to_id_.find(kGLSLstd450);
    if (set_iter == import_name_to_id_.end()) {
      error_ = std::string("unknown import ") + kGLSLstd450;
      return 0;
    }
    auto set_id = set_iter->second;
    auto inst_id =
        intrinsic_to_glsl_method(ident->result_type(), ident->intrinsic());
    if (inst_id == 0) {
      error_ = "unknown method " + ident->name();
      return 0;
    }

    params.push_back(Operand::Int(set_id));
    params.push_back(Operand::Int(inst_id));

    op = spv::Op::OpExtInst;
  }

  if (op == spv::Op::OpNop) {
    error_ = "unable to determine operator for: " + ident->name();
    return 0;
  }

  for (auto* p : call->params()) {
    auto val_id = GenerateExpression(p);
    if (val_id == 0) {
      return false;
    }
    val_id = GenerateLoadIfNeeded(p->result_type(), val_id);

    params.emplace_back(Operand::Int(val_id));
  }

  push_function_inst(op, params);

  return result_id;
}

void Builder::GenerateTextureIntrinsic(ast::IdentifierExpression* ident,
                                       ast::CallExpression* call,
                                       spirv::Operand result_type,
                                       spirv::Operand result_id) {
  auto* texture_type =
      call->params()[0]->result_type()->UnwrapAll()->AsTexture();

  auto* sig = static_cast<const ast::intrinsic::TextureSignature*>(
      ident->intrinsic_signature());
  assert(sig != nullptr);
  auto& pidx = sig->params.idx;
  auto const kNotUsed = ast::intrinsic::TextureSignature::Parameters::kNotUsed;

  assert(pidx.texture != kNotUsed);

  auto op = spv::Op::OpNop;

  auto gen_param = [&](size_t idx) {
    auto* p = call->params()[idx];
    auto val_id = GenerateExpression(p);
    if (val_id == 0) {
      return Operand::Int(0);
    }
    val_id = GenerateLoadIfNeeded(p->result_type(), val_id);

    return Operand::Int(val_id);
  };

  // Populate the spirv_params with common parameters
  OperandList spirv_params;
  spirv_params.reserve(8);  // Enough to fit most parameter lists
  spirv_params.emplace_back(std::move(result_type));  // result type
  spirv_params.emplace_back(std::move(result_id));    // result id

  // Extra image operands, appended to spirv_params.
  uint32_t spirv_operand_mask = 0;
  OperandList spirv_operands;
  spirv_operands.reserve(4);  // Enough to fit most parameter lists

  if (ident->intrinsic() == ast::Intrinsic::kTextureLoad) {
    op = texture_type->IsStorage() ? spv::Op::OpImageRead
                                   : spv::Op::OpImageFetch;
    spirv_params.emplace_back(gen_param(pidx.texture));
    spirv_params.emplace_back(gen_param(pidx.coords));

    // TODO(dsinclair): Remove the LOD param from textureLoad on storage
    // textures when https://github.com/gpuweb/gpuweb/pull/1032 gets merged.
    if (pidx.level != kNotUsed) {
      if (texture_type->IsMultisampled()) {
        spirv_operand_mask |= SpvImageOperandsSampleMask;
      } else {
        spirv_operand_mask |= SpvImageOperandsLodMask;
      }
      spirv_operands.emplace_back(gen_param(pidx.level));
    }
  } else {
    assert(pidx.sampler != kNotUsed);

    auto sampler_param = gen_param(pidx.sampler);
    auto texture_param = gen_param(pidx.texture);
    auto sampled_image =
        GenerateSampledImage(texture_type, texture_param, sampler_param);

    // Populate the spirv_params with the common parameters
    spirv_params.emplace_back(Operand::Int(sampled_image));  // sampled image

    if (pidx.array_index != kNotUsed) {
      // Array index needs to be appended to the coordinates.
      auto* param_coords = call->params()[pidx.coords];
      auto* param_array_index = call->params()[pidx.array_index];

      uint32_t packed_coords_size;
      ast::type::Type* packed_coords_el_ty;  // Currenly must be f32.
      if (param_coords->result_type()->IsVector()) {
        auto* vec = param_coords->result_type()->AsVector();
        packed_coords_size = vec->size() + 1;
        packed_coords_el_ty = vec->type();
      } else {
        packed_coords_size = 2;
        packed_coords_el_ty = param_coords->result_type();
      }

      // Cast param_array_index to the vector element type
      ast::TypeConstructorExpression array_index_cast(packed_coords_el_ty,
                                                      {param_array_index});
      array_index_cast.set_result_type(packed_coords_el_ty);

      ast::type::VectorType packed_coords_ty(packed_coords_el_ty,
                                             packed_coords_size);

      ast::TypeConstructorExpression constructor{
          &packed_coords_ty, {param_coords, &array_index_cast}};
      auto packed_coords =
          GenerateTypeConstructorExpression(&constructor, false);

      spirv_params.emplace_back(Operand::Int(packed_coords));  // coordinates

    } else {
      spirv_params.emplace_back(gen_param(pidx.coords));  // coordinates
    }

    switch (ident->intrinsic()) {
      case ast::Intrinsic::kTextureSample: {
        op = spv::Op::OpImageSampleImplicitLod;
        break;
      }
      case ast::Intrinsic::kTextureSampleBias: {
        op = spv::Op::OpImageSampleImplicitLod;
        assert(pidx.bias != kNotUsed);
        spirv_operand_mask |= SpvImageOperandsBiasMask;
        spirv_operands.emplace_back(gen_param(pidx.bias));
        break;
      }
      case ast::Intrinsic::kTextureSampleLevel: {
        op = spv::Op::OpImageSampleExplicitLod;
        assert(pidx.level != kNotUsed);
        spirv_operand_mask |= SpvImageOperandsLodMask;
        spirv_operands.emplace_back(gen_param(pidx.level));
        break;
      }
      case ast::Intrinsic::kTextureSampleGrad: {
        op = spv::Op::OpImageSampleExplicitLod;
        assert(pidx.ddx != kNotUsed);
        assert(pidx.ddy != kNotUsed);
        spirv_operand_mask |= SpvImageOperandsGradMask;
        spirv_operands.emplace_back(gen_param(pidx.ddx));
        spirv_operands.emplace_back(gen_param(pidx.ddy));
        break;
      }
      case ast::Intrinsic::kTextureSampleCompare: {
        op = spv::Op::OpImageSampleDrefExplicitLod;
        assert(pidx.depth_ref != kNotUsed);
        spirv_params.emplace_back(gen_param(pidx.depth_ref));

        spirv_operand_mask |= SpvImageOperandsLodMask;
        ast::type::F32Type f32;
        ast::FloatLiteral float_0(&f32, 0.0);
        spirv_operands.emplace_back(
            Operand::Int(GenerateLiteralIfNeeded(nullptr, &float_0)));
        break;
      }
      default:
        break;  // unreachable
    }
  }

  if (pidx.offset != kNotUsed) {
    spirv_operand_mask |= SpvImageOperandsOffsetMask;
    spirv_operands.emplace_back(gen_param(pidx.offset));
  }

  if (spirv_operand_mask != 0) {
    // Note: Order of operands is based on SpvImageXXXOperands value -
    // smaller-numbered SpvImageXXXOperands bits appear first.
    spirv_params.emplace_back(Operand::Int(spirv_operand_mask));
    spirv_params.insert(std::end(spirv_params), std::begin(spirv_operands),
                        std::end(spirv_operands));
  }

  if (op == spv::Op::OpNop) {
    error_ = "unable to determine operator for: " + ident->name();
    return;
  }

  push_function_inst(op, spirv_params);
}

uint32_t Builder::GenerateSampledImage(ast::type::Type* texture_type,
                                       Operand texture_operand,
                                       Operand sampler_operand) {
  uint32_t sampled_image_type_id = 0;
  auto val = texture_type_name_to_sampled_image_type_id_.find(
      texture_type->type_name());
  if (val != texture_type_name_to_sampled_image_type_id_.end()) {
    // The sampled image type is already created.
    sampled_image_type_id = val->second;
  } else {
    // We need to create the sampled image type and cache the result.
    auto sampled_image_type = result_op();
    sampled_image_type_id = sampled_image_type.to_i();
    auto texture_type_id = GenerateTypeIfNeeded(texture_type);
    push_type(spv::Op::OpTypeSampledImage,
              {sampled_image_type, Operand::Int(texture_type_id)});
    texture_type_name_to_sampled_image_type_id_[texture_type->type_name()] =
        sampled_image_type_id;
  }

  auto sampled_image = result_op();
  push_function_inst(spv::Op::OpSampledImage,
                     {Operand::Int(sampled_image_type_id), sampled_image,
                      texture_operand, sampler_operand});

  return sampled_image.to_i();
}

uint32_t Builder::GenerateBitcastExpression(ast::BitcastExpression* expr) {
  auto result = result_op();
  auto result_id = result.to_i();

  auto result_type_id = GenerateTypeIfNeeded(expr->result_type());
  if (result_type_id == 0) {
    return 0;
  }

  auto val_id = GenerateExpression(expr->expr());
  if (val_id == 0) {
    return 0;
  }
  val_id = GenerateLoadIfNeeded(expr->expr()->result_type(), val_id);

  // Bitcast does not allow same types, just emit a CopyObject
  auto* to_type = expr->result_type()->UnwrapPtrIfNeeded();
  auto* from_type = expr->expr()->result_type()->UnwrapPtrIfNeeded();
  if (to_type->type_name() == from_type->type_name()) {
    push_function_inst(spv::Op::OpCopyObject, {Operand::Int(result_type_id),
                                               result, Operand::Int(val_id)});
    return result_id;
  }

  push_function_inst(spv::Op::OpBitcast, {Operand::Int(result_type_id), result,
                                          Operand::Int(val_id)});

  return result_id;
}

bool Builder::GenerateConditionalBlock(
    ast::Expression* cond,
    const ast::BlockStatement* true_body,
    size_t cur_else_idx,
    const ast::ElseStatementList& else_stmts) {
  auto cond_id = GenerateExpression(cond);
  if (cond_id == 0) {
    return false;
  }
  cond_id = GenerateLoadIfNeeded(cond->result_type(), cond_id);

  auto merge_block = result_op();
  auto merge_block_id = merge_block.to_i();

  push_function_inst(spv::Op::OpSelectionMerge,
                     {Operand::Int(merge_block_id),
                      Operand::Int(SpvSelectionControlMaskNone)});

  auto true_block = result_op();
  auto true_block_id = true_block.to_i();

  // if there are no more else statements we branch on false to the merge block
  // otherwise we branch to the false block
  auto false_block_id =
      cur_else_idx < else_stmts.size() ? next_id() : merge_block_id;

  push_function_inst(spv::Op::OpBranchConditional,
                     {Operand::Int(cond_id), Operand::Int(true_block_id),
                      Operand::Int(false_block_id)});

  // Output true block
  GenerateLabel(true_block_id);
  if (!GenerateBlockStatement(true_body)) {
    return false;
  }
  // We only branch if the last element of the body didn't already branch.
  if (!LastIsTerminator(true_body)) {
    push_function_inst(spv::Op::OpBranch, {Operand::Int(merge_block_id)});
  }

  // Start the false block if needed
  if (false_block_id != merge_block_id) {
    GenerateLabel(false_block_id);

    auto* else_stmt = else_stmts[cur_else_idx];
    // Handle the else case by just outputting the statements.
    if (!else_stmt->HasCondition()) {
      if (!GenerateBlockStatement(else_stmt->body())) {
        return false;
      }
    } else {
      if (!GenerateConditionalBlock(else_stmt->condition(), else_stmt->body(),
                                    cur_else_idx + 1, else_stmts)) {
        return false;
      }
    }
    if (!LastIsTerminator(else_stmt->body())) {
      push_function_inst(spv::Op::OpBranch, {Operand::Int(merge_block_id)});
    }
  }

  // Output the merge block
  GenerateLabel(merge_block_id);

  return true;
}

bool Builder::GenerateIfStatement(ast::IfStatement* stmt) {
  if (!GenerateConditionalBlock(stmt->condition(), stmt->body(), 0,
                                stmt->else_statements())) {
    return false;
  }
  return true;
}

bool Builder::GenerateSwitchStatement(ast::SwitchStatement* stmt) {
  auto merge_block = result_op();
  auto merge_block_id = merge_block.to_i();

  merge_stack_.push_back(merge_block_id);

  auto cond_id = GenerateExpression(stmt->condition());
  if (cond_id == 0) {
    return false;
  }
  cond_id = GenerateLoadIfNeeded(stmt->condition()->result_type(), cond_id);

  auto default_block = result_op();
  auto default_block_id = default_block.to_i();

  OperandList params = {Operand::Int(cond_id), Operand::Int(default_block_id)};

  std::vector<uint32_t> case_ids;
  for (const auto* item : stmt->body()) {
    if (item->IsDefault()) {
      case_ids.push_back(default_block_id);
      continue;
    }

    auto block = result_op();
    auto block_id = block.to_i();

    case_ids.push_back(block_id);
    for (auto* selector : item->selectors()) {
      if (!selector->IsSint()) {
        error_ = "expected integer literal for switch case label";
        return false;
      }

      params.push_back(Operand::Int(selector->AsSint()->value()));
      params.push_back(Operand::Int(block_id));
    }
  }

  push_function_inst(spv::Op::OpSelectionMerge,
                     {Operand::Int(merge_block_id),
                      Operand::Int(SpvSelectionControlMaskNone)});
  push_function_inst(spv::Op::OpSwitch, params);

  bool generated_default = false;
  auto& body = stmt->body();
  // We output the case statements in order they were entered in the original
  // source. Each fallthrough goes to the next case entry, so is a forward
  // branch, otherwise the branch is to the merge block which comes after
  // the switch statement.
  for (uint32_t i = 0; i < body.size(); i++) {
    auto* item = body[i];

    if (item->IsDefault()) {
      generated_default = true;
    }

    GenerateLabel(case_ids[i]);
    if (!GenerateBlockStatement(item->body())) {
      return false;
    }

    if (LastIsFallthrough(item->body())) {
      if (i == (body.size() - 1)) {
        error_ = "fallthrough of last case statement is disallowed";
        return false;
      }
      push_function_inst(spv::Op::OpBranch, {Operand::Int(case_ids[i + 1])});
    } else if (!LastIsTerminator(item->body())) {
      push_function_inst(spv::Op::OpBranch, {Operand::Int(merge_block_id)});
    }
  }

  if (!generated_default) {
    GenerateLabel(default_block_id);
    push_function_inst(spv::Op::OpBranch, {Operand::Int(merge_block_id)});
  }

  merge_stack_.pop_back();

  GenerateLabel(merge_block_id);
  return true;
}

bool Builder::GenerateReturnStatement(ast::ReturnStatement* stmt) {
  if (stmt->has_value()) {
    auto val_id = GenerateExpression(stmt->value());
    if (val_id == 0) {
      return false;
    }
    val_id = GenerateLoadIfNeeded(stmt->value()->result_type(), val_id);
    push_function_inst(spv::Op::OpReturnValue, {Operand::Int(val_id)});
  } else {
    push_function_inst(spv::Op::OpReturn, {});
  }

  return true;
}

bool Builder::GenerateLoopStatement(ast::LoopStatement* stmt) {
  auto loop_header = result_op();
  auto loop_header_id = loop_header.to_i();
  push_function_inst(spv::Op::OpBranch, {Operand::Int(loop_header_id)});
  GenerateLabel(loop_header_id);

  auto merge_block = result_op();
  auto merge_block_id = merge_block.to_i();
  auto continue_block = result_op();
  auto continue_block_id = continue_block.to_i();

  auto body_block = result_op();
  auto body_block_id = body_block.to_i();

  push_function_inst(
      spv::Op::OpLoopMerge,
      {Operand::Int(merge_block_id), Operand::Int(continue_block_id),
       Operand::Int(SpvLoopControlMaskNone)});

  continue_stack_.push_back(continue_block_id);
  merge_stack_.push_back(merge_block_id);

  push_function_inst(spv::Op::OpBranch, {Operand::Int(body_block_id)});
  GenerateLabel(body_block_id);
  if (!GenerateBlockStatement(stmt->body())) {
    return false;
  }

  // We only branch if the last element of the body didn't already branch.
  if (!LastIsTerminator(stmt->body())) {
    push_function_inst(spv::Op::OpBranch, {Operand::Int(continue_block_id)});
  }

  GenerateLabel(continue_block_id);
  if (!GenerateBlockStatement(stmt->continuing())) {
    return false;
  }
  push_function_inst(spv::Op::OpBranch, {Operand::Int(loop_header_id)});

  merge_stack_.pop_back();
  continue_stack_.pop_back();

  GenerateLabel(merge_block_id);

  return true;
}

bool Builder::GenerateStatement(ast::Statement* stmt) {
  if (stmt->IsAssign()) {
    return GenerateAssignStatement(stmt->AsAssign());
  }
  if (stmt->IsBlock()) {
    return GenerateBlockStatement(stmt->AsBlock());
  }
  if (stmt->IsBreak()) {
    return GenerateBreakStatement(stmt->AsBreak());
  }
  if (stmt->IsCall()) {
    return GenerateCallExpression(stmt->AsCall()->expr()) != 0;
  }
  if (stmt->IsContinue()) {
    return GenerateContinueStatement(stmt->AsContinue());
  }
  if (stmt->IsDiscard()) {
    return GenerateDiscardStatement(stmt->AsDiscard());
  }
  if (stmt->IsFallthrough()) {
    // Do nothing here, the fallthrough gets handled by the switch code.
    return true;
  }
  if (stmt->IsIf()) {
    return GenerateIfStatement(stmt->AsIf());
  }
  if (stmt->IsLoop()) {
    return GenerateLoopStatement(stmt->AsLoop());
  }
  if (stmt->IsReturn()) {
    return GenerateReturnStatement(stmt->AsReturn());
  }
  if (stmt->IsSwitch()) {
    return GenerateSwitchStatement(stmt->AsSwitch());
  }
  if (stmt->IsVariableDecl()) {
    return GenerateVariableDeclStatement(stmt->AsVariableDecl());
  }

  error_ = "Unknown statement: " + stmt->str();
  return false;
}

bool Builder::GenerateVariableDeclStatement(ast::VariableDeclStatement* stmt) {
  return GenerateFunctionVariable(stmt->variable());
}

uint32_t Builder::GenerateTypeIfNeeded(ast::type::Type* type) {
  if (type == nullptr) {
    error_ = "attempting to generate type from null type";
    return 0;
  }

  // The alias is a wrapper around the subtype, so emit the subtype
  if (type->IsAlias()) {
    return GenerateTypeIfNeeded(type->AsAlias()->type());
  }

  auto val = type_name_to_id_.find(type->type_name());
  if (val != type_name_to_id_.end()) {
    return val->second;
  }

  auto result = result_op();
  auto id = result.to_i();

  if (type->IsAccessControl()) {
    auto* ac = type->AsAccessControl();
    auto* subtype = ac->type()->UnwrapIfNeeded();
    if (!subtype->IsStruct()) {
      error_ = "Access control attached to non-struct type.";
      return 0;
    }
    if (!GenerateStructType(subtype->AsStruct(), ac->access_control(),
                            result)) {
      return 0;
    }
  } else if (type->IsArray()) {
    if (!GenerateArrayType(type->AsArray(), result)) {
      return 0;
    }
  } else if (type->IsBool()) {
    push_type(spv::Op::OpTypeBool, {result});
  } else if (type->IsF32()) {
    push_type(spv::Op::OpTypeFloat, {result, Operand::Int(32)});
  } else if (type->IsI32()) {
    push_type(spv::Op::OpTypeInt, {result, Operand::Int(32), Operand::Int(1)});
  } else if (type->IsMatrix()) {
    if (!GenerateMatrixType(type->AsMatrix(), result)) {
      return 0;
    }
  } else if (type->IsPointer()) {
    if (!GeneratePointerType(type->AsPointer(), result)) {
      return 0;
    }
  } else if (type->IsStruct()) {
    if (!GenerateStructType(type->AsStruct(), ast::AccessControl::kReadWrite,
                            result)) {
      return 0;
    }
  } else if (type->IsU32()) {
    push_type(spv::Op::OpTypeInt, {result, Operand::Int(32), Operand::Int(0)});
  } else if (type->IsVector()) {
    if (!GenerateVectorType(type->AsVector(), result)) {
      return 0;
    }
  } else if (type->IsVoid()) {
    push_type(spv::Op::OpTypeVoid, {result});
  } else if (type->IsTexture()) {
    if (!GenerateTextureType(type->AsTexture(), result)) {
      return 0;
    }
  } else if (type->IsSampler()) {
    push_type(spv::Op::OpTypeSampler, {result});

    // Register both of the sampler type names. In SPIR-V they're the same
    // sampler type, so we need to match that when we do the dedup check.
    type_name_to_id_["__sampler_sampler"] = id;
    type_name_to_id_["__sampler_comparison"] = id;

  } else {
    error_ = "unable to convert type: " + type->type_name();
    return 0;
  }

  type_name_to_id_[type->type_name()] = id;
  return id;
}

// TODO(tommek): Cover multisampled textures here when they're included in AST
bool Builder::GenerateTextureType(ast::type::TextureType* texture,
                                  const Operand& result) {
  uint32_t array_literal = 0u;
  auto dim = texture->dim();
  if (dim == ast::type::TextureDimension::k1dArray ||
      dim == ast::type::TextureDimension::k2dArray ||
      dim == ast::type::TextureDimension::kCubeArray) {
    array_literal = 1u;
  }

  uint32_t dim_literal = SpvDim2D;
  if (dim == ast::type::TextureDimension::k1dArray ||
      dim == ast::type::TextureDimension::k1d) {
    dim_literal = SpvDim1D;
  }
  if (dim == ast::type::TextureDimension::k3d) {
    dim_literal = SpvDim3D;
  }
  if (dim == ast::type::TextureDimension::kCube ||
      dim == ast::type::TextureDimension::kCubeArray) {
    dim_literal = SpvDimCube;
  }

  uint32_t ms_literal = 0u;
  if (texture->IsMultisampled()) {
    ms_literal = 1u;
  }

  uint32_t depth_literal = 0u;
  if (texture->IsDepth()) {
    depth_literal = 1u;
  }

  uint32_t sampled_literal = 2u;
  if (texture->IsMultisampled() || texture->IsSampled() || texture->IsDepth()) {
    sampled_literal = 1u;
  }

  uint32_t type_id = 0u;
  if (texture->IsDepth()) {
    ast::type::F32Type f32;
    type_id = GenerateTypeIfNeeded(&f32);
  } else if (texture->IsSampled()) {
    type_id = GenerateTypeIfNeeded(texture->AsSampled()->type());
  } else if (texture->IsMultisampled()) {
    type_id = GenerateTypeIfNeeded(texture->AsMultisampled()->type());
  } else if (texture->IsStorage()) {
    if (texture->AsStorage()->access() == ast::AccessControl::kWriteOnly) {
      ast::type::VoidType void_type;
      type_id = GenerateTypeIfNeeded(&void_type);
    } else {
      type_id = GenerateTypeIfNeeded(texture->AsStorage()->type());
    }
  }
  if (type_id == 0u) {
    return false;
  }

  uint32_t format_literal = SpvImageFormat_::SpvImageFormatUnknown;
  if (texture->IsStorage()) {
    format_literal =
        convert_image_format_to_spv(texture->AsStorage()->image_format());
  }

  push_type(spv::Op::OpTypeImage,
            {result, Operand::Int(type_id), Operand::Int(dim_literal),
             Operand::Int(depth_literal), Operand::Int(array_literal),
             Operand::Int(ms_literal), Operand::Int(sampled_literal),
             Operand::Int(format_literal)});

  return true;
}

bool Builder::GenerateArrayType(ast::type::ArrayType* ary,
                                const Operand& result) {
  auto elem_type = GenerateTypeIfNeeded(ary->type());
  if (elem_type == 0) {
    return false;
  }

  auto result_id = result.to_i();
  if (ary->IsRuntimeArray()) {
    push_type(spv::Op::OpTypeRuntimeArray, {result, Operand::Int(elem_type)});
  } else {
    auto len_id = GenerateU32Literal(ary->size());
    if (len_id == 0) {
      return false;
    }

    push_type(spv::Op::OpTypeArray,
              {result, Operand::Int(elem_type), Operand::Int(len_id)});
  }

  if (ary->has_array_stride()) {
    push_annot(spv::Op::OpDecorate,
               {Operand::Int(result_id), Operand::Int(SpvDecorationArrayStride),
                Operand::Int(ary->array_stride())});
  }
  return true;
}

bool Builder::GenerateMatrixType(ast::type::MatrixType* mat,
                                 const Operand& result) {
  ast::type::VectorType col_type(mat->type(), mat->rows());
  auto col_type_id = GenerateTypeIfNeeded(&col_type);
  if (has_error()) {
    return false;
  }

  push_type(spv::Op::OpTypeMatrix,
            {result, Operand::Int(col_type_id), Operand::Int(mat->columns())});
  return true;
}

bool Builder::GeneratePointerType(ast::type::PointerType* ptr,
                                  const Operand& result) {
  auto pointee_id = GenerateTypeIfNeeded(ptr->type());
  if (pointee_id == 0) {
    return false;
  }

  auto stg_class = ConvertStorageClass(ptr->storage_class());
  if (stg_class == SpvStorageClassMax) {
    error_ = "invalid storage class for pointer";
    return false;
  }

  push_type(spv::Op::OpTypePointer,
            {result, Operand::Int(stg_class), Operand::Int(pointee_id)});

  return true;
}

bool Builder::GenerateStructType(ast::type::StructType* struct_type,
                                 ast::AccessControl access_control,
                                 const Operand& result) {
  auto struct_id = result.to_i();
  auto* impl = struct_type->impl();

  if (!struct_type->name().empty()) {
    push_debug(spv::Op::OpName,
               {Operand::Int(struct_id),
                Operand::String(ctx_->namer()->NameFor(struct_type->name()))});
  }

  OperandList ops;
  ops.push_back(result);

  if (impl->IsBlockDecorated()) {
    push_annot(spv::Op::OpDecorate,
               {Operand::Int(struct_id), Operand::Int(SpvDecorationBlock)});
  }

  auto& members = impl->members();
  for (uint32_t i = 0; i < members.size(); ++i) {
    auto mem_id = GenerateStructMember(struct_id, i, members[i]);
    if (mem_id == 0) {
      return false;
    }

    // We're attaching the access control to the members of the struct instead
    // of to the variable. The reason we do this is that WGSL models the access
    // as part of the type. If we attach to the variable, it's no longer part
    // of the type in the SPIR-V backend, but part of the variable. This differs
    // from the modeling and other backends. Attaching to the struct members
    // means the access control stays part of the type where it logically makes
    // the most sense.
    if (access_control == ast::AccessControl::kReadOnly) {
      push_annot(spv::Op::OpMemberDecorate,
                 {Operand::Int(struct_id), Operand::Int(i),
                  Operand::Int(SpvDecorationNonWritable)});
    }

    ops.push_back(Operand::Int(mem_id));
  }

  push_type(spv::Op::OpTypeStruct, std::move(ops));
  return true;
}

uint32_t Builder::GenerateStructMember(uint32_t struct_id,
                                       uint32_t idx,
                                       ast::StructMember* member) {
  push_debug(spv::Op::OpMemberName,
             {Operand::Int(struct_id), Operand::Int(idx),
              Operand::String(ctx_->namer()->NameFor(member->name()))});

  bool has_layout = false;
  for (auto* deco : member->decorations()) {
    if (deco->IsOffset()) {
      push_annot(spv::Op::OpMemberDecorate,
                 {Operand::Int(struct_id), Operand::Int(idx),
                  Operand::Int(SpvDecorationOffset),
                  Operand::Int(deco->AsOffset()->offset())});
      has_layout = true;
    } else {
      error_ = "unknown struct member decoration";
      return 0;
    }
  }

  if (has_layout) {
    // Infer and emit matrix layout.
    auto* matrix_type = GetNestedMatrixType(member->type());
    if (matrix_type) {
      push_annot(spv::Op::OpMemberDecorate,
                 {Operand::Int(struct_id), Operand::Int(idx),
                  Operand::Int(SpvDecorationColMajor)});
      if (!matrix_type->type()->IsF32()) {
        error_ = "matrix scalar element type must be f32";
        return 0;
      }
      const auto scalar_elem_size = 4;
      const auto effective_row_count = (matrix_type->rows() == 2) ? 2 : 4;
      push_annot(spv::Op::OpMemberDecorate,
                 {Operand::Int(struct_id), Operand::Int(idx),
                  Operand::Int(SpvDecorationMatrixStride),
                  Operand::Int(effective_row_count * scalar_elem_size)});
    }
  }

  return GenerateTypeIfNeeded(member->type());
}

bool Builder::GenerateVectorType(ast::type::VectorType* vec,
                                 const Operand& result) {
  auto type_id = GenerateTypeIfNeeded(vec->type());
  if (has_error()) {
    return false;
  }

  push_type(spv::Op::OpTypeVector,
            {result, Operand::Int(type_id), Operand::Int(vec->size())});
  return true;
}

SpvStorageClass Builder::ConvertStorageClass(ast::StorageClass klass) const {
  switch (klass) {
    case ast::StorageClass::kInput:
      return SpvStorageClassInput;
    case ast::StorageClass::kOutput:
      return SpvStorageClassOutput;
    case ast::StorageClass::kUniform:
      return SpvStorageClassUniform;
    case ast::StorageClass::kWorkgroup:
      return SpvStorageClassWorkgroup;
    case ast::StorageClass::kUniformConstant:
      return SpvStorageClassUniformConstant;
    case ast::StorageClass::kStorageBuffer:
      return SpvStorageClassStorageBuffer;
    case ast::StorageClass::kImage:
      return SpvStorageClassImage;
    case ast::StorageClass::kPrivate:
      return SpvStorageClassPrivate;
    case ast::StorageClass::kFunction:
      return SpvStorageClassFunction;
    case ast::StorageClass::kNone:
      break;
  }
  return SpvStorageClassMax;
}

SpvBuiltIn Builder::ConvertBuiltin(ast::Builtin builtin) const {
  switch (builtin) {
    case ast::Builtin::kPosition:
      return SpvBuiltInPosition;
    case ast::Builtin::kVertexIdx:
      return SpvBuiltInVertexIndex;
    case ast::Builtin::kInstanceIdx:
      return SpvBuiltInInstanceIndex;
    case ast::Builtin::kFrontFacing:
      return SpvBuiltInFrontFacing;
    case ast::Builtin::kFragCoord:
      return SpvBuiltInFragCoord;
    case ast::Builtin::kFragDepth:
      return SpvBuiltInFragDepth;
    case ast::Builtin::kLocalInvocationId:
      return SpvBuiltInLocalInvocationId;
    case ast::Builtin::kLocalInvocationIdx:
      return SpvBuiltInLocalInvocationIndex;
    case ast::Builtin::kGlobalInvocationId:
      return SpvBuiltInGlobalInvocationId;
    case ast::Builtin::kNone:
      break;
  }
  return SpvBuiltInMax;
}

SpvImageFormat Builder::convert_image_format_to_spv(
    const ast::type::ImageFormat format) {
  switch (format) {
    case ast::type::ImageFormat::kR8Unorm:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR8;
    case ast::type::ImageFormat::kR8Snorm:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR8Snorm;
    case ast::type::ImageFormat::kR8Uint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR8ui;
    case ast::type::ImageFormat::kR8Sint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR8i;
    case ast::type::ImageFormat::kR16Uint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR16ui;
    case ast::type::ImageFormat::kR16Sint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR16i;
    case ast::type::ImageFormat::kR16Float:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR16f;
    case ast::type::ImageFormat::kRg8Unorm:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg8;
    case ast::type::ImageFormat::kRg8Snorm:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg8Snorm;
    case ast::type::ImageFormat::kRg8Uint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg8ui;
    case ast::type::ImageFormat::kRg8Sint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg8i;
    case ast::type::ImageFormat::kR32Uint:
      return SpvImageFormatR32ui;
    case ast::type::ImageFormat::kR32Sint:
      return SpvImageFormatR32i;
    case ast::type::ImageFormat::kR32Float:
      return SpvImageFormatR32f;
    case ast::type::ImageFormat::kRg16Uint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg16ui;
    case ast::type::ImageFormat::kRg16Sint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg16i;
    case ast::type::ImageFormat::kRg16Float:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg16f;
    case ast::type::ImageFormat::kRgba8Unorm:
      return SpvImageFormatRgba8;
    case ast::type::ImageFormat::kRgba8UnormSrgb:
      return SpvImageFormatUnknown;
    case ast::type::ImageFormat::kRgba8Snorm:
      return SpvImageFormatRgba8Snorm;
    case ast::type::ImageFormat::kRgba8Uint:
      return SpvImageFormatRgba8ui;
    case ast::type::ImageFormat::kRgba8Sint:
      return SpvImageFormatRgba8i;
    case ast::type::ImageFormat::kBgra8Unorm:
      return SpvImageFormatUnknown;
    case ast::type::ImageFormat::kBgra8UnormSrgb:
      return SpvImageFormatUnknown;
    case ast::type::ImageFormat::kRgb10A2Unorm:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRgb10A2;
    case ast::type::ImageFormat::kRg11B10Float:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatR11fG11fB10f;
    case ast::type::ImageFormat::kRg32Uint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg32ui;
    case ast::type::ImageFormat::kRg32Sint:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg32i;
    case ast::type::ImageFormat::kRg32Float:
      push_capability(SpvCapabilityStorageImageExtendedFormats);
      return SpvImageFormatRg32f;
    case ast::type::ImageFormat::kRgba16Uint:
      return SpvImageFormatRgba16ui;
    case ast::type::ImageFormat::kRgba16Sint:
      return SpvImageFormatRgba16i;
    case ast::type::ImageFormat::kRgba16Float:
      return SpvImageFormatRgba16f;
    case ast::type::ImageFormat::kRgba32Uint:
      return SpvImageFormatRgba32ui;
    case ast::type::ImageFormat::kRgba32Sint:
      return SpvImageFormatRgba32i;
    case ast::type::ImageFormat::kRgba32Float:
      return SpvImageFormatRgba32f;
    case ast::type::ImageFormat::kNone:
      return SpvImageFormatUnknown;
  }
  return SpvImageFormatUnknown;
}

}  // namespace spirv
}  // namespace writer
}  // namespace tint