src/tint/lang/spirv/writer/ast_printer/builder.h

// Copyright 2020 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef SRC_TINT_LANG_SPIRV_WRITER_AST_PRINTER_BUILDER_H_
#define SRC_TINT_LANG_SPIRV_WRITER_AST_PRINTER_BUILDER_H_

#include <memory>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "spirv/unified1/spirv.h"
#include "src/tint/lang/core/builtin_value.h"
#include "src/tint/lang/core/type/storage_texture.h"
#include "src/tint/lang/spirv/writer/ast_printer/scalar_constant.h"
#include "src/tint/lang/spirv/writer/common/function.h"
#include "src/tint/lang/spirv/writer/common/module.h"
#include "src/tint/lang/wgsl/ast/assignment_statement.h"
#include "src/tint/lang/wgsl/ast/bitcast_expression.h"
#include "src/tint/lang/wgsl/ast/break_statement.h"
#include "src/tint/lang/wgsl/ast/continue_statement.h"
#include "src/tint/lang/wgsl/ast/discard_statement.h"
#include "src/tint/lang/wgsl/ast/if_statement.h"
#include "src/tint/lang/wgsl/ast/interpolate_attribute.h"
#include "src/tint/lang/wgsl/ast/loop_statement.h"
#include "src/tint/lang/wgsl/ast/return_statement.h"
#include "src/tint/lang/wgsl/ast/switch_statement.h"
#include "src/tint/lang/wgsl/ast/unary_op_expression.h"
#include "src/tint/lang/wgsl/ast/variable_decl_statement.h"
#include "src/tint/lang/wgsl/program/program_builder.h"
#include "src/tint/lang/wgsl/sem/builtin_fn.h"
#include "src/tint/utils/containers/scope_stack.h"

// Forward declarations
namespace tint::sem {
class Call;
class Load;
class ValueConstructor;
class ValueConversion;
}  // namespace tint::sem
namespace tint::core::type {
class Reference;
}  // namespace tint::core::type

namespace tint::spirv::writer {

/// Builder class to create a SPIR-V module from a Tint AST.
class Builder {
  public:
    /// Contains information for generating accessor chains
    struct AccessorInfo {
        AccessorInfo();
        ~AccessorInfo();

        /// The ID of the current chain source. The chain source may change as we
        /// evaluate the access chain. The chain source always points to the ID
        /// which we will use to evaluate the current set of accessors. This maybe
        /// the original variable, or maybe an intermediary if we had to evaulate
        /// the access chain early (in the case of a swizzle of an access chain).
        uint32_t source_id;
        /// The type of the current chain source. This type matches the deduced
        /// result_type of the current source defined above.
        const core::type::Type* source_type;
        /// A list of access chain indices to emit. Note, we _only_ have access
        /// chain indices if the source is reference.
        std::vector<uint32_t> access_chain_indices;
    };

    /// Constructor
    /// @param program the program
    /// @param zero_initialize_workgroup_memory `true` to initialize all the
    /// variables in the Workgroup address space with OpConstantNull
    /// @param experimental_require_subgroup_uniform_control_flow `true` to require
    /// `SPV_KHR_subgroup_uniform_control_flow` extension and `SubgroupUniformControlFlowKHR`
    /// execution mode for compute stage entry points.
    explicit Builder(const Program& program,
                     bool zero_initialize_workgroup_memory = false,
                     bool experimental_require_subgroup_uniform_control_flow = false);
    ~Builder();

    /// Generates the SPIR-V instructions for the given program
    /// @returns true if the SPIR-V was successfully built
    bool Build();

    /// @returns the list of diagnostics raised by the builder
    const diag::List& Diagnostics() const { return builder_.Diagnostics(); }

    /// @returns true if the builder encountered an error
    bool has_error() const { return Diagnostics().contains_errors(); }

    /// @returns the module that this builder has produced
    writer::Module& Module() { return module_; }

    /// Add an empty function to the builder, to be used for testing purposes.
    void PushFunctionForTesting() {
        current_function_ = Function(Instruction(spv::Op::OpFunction, {}), {}, {});
    }

    /// @returns the current function
    const Function& CurrentFunction() { return current_function_; }

    /// Pushes an instruction to the current function. If we're outside
    /// a function then issue an internal error and return false.
    /// @param op the operation
    /// @param operands the operands
    /// @returns true if we succeeded
    bool push_function_inst(spv::Op op, const OperandList& operands);
    /// Pushes a variable to the current function
    /// @param operands the variable operands
    void push_function_var(const OperandList& operands) {
        if (TINT_UNLIKELY(!current_function_)) {
            TINT_ICE() << "push_function_var() called without a function";
        }
        current_function_.push_var(operands);
    }

    /// @returns true if the current instruction insertion point is
    /// inside a basic block.
    bool InsideBasicBlock() const;

    /// Converts a address space to a SPIR-V address space.
    /// @param klass the address space to convert
    /// @returns the SPIR-V address space or SpvStorageClassMax on error.
    SpvStorageClass ConvertAddressSpace(core::AddressSpace klass) const;
    /// Converts a builtin to a SPIR-V builtin and pushes a capability if needed.
    /// @param builtin the builtin to convert
    /// @param storage the address space that this builtin is being used with
    /// @returns the SPIR-V builtin or SpvBuiltInMax on error.
    SpvBuiltIn ConvertBuiltin(core::BuiltinValue builtin, core::AddressSpace storage);

    /// Converts an interpolate attribute to SPIR-V decorations and pushes a
    /// capability if needed.
    /// @param id the id to decorate
    /// @param type the interpolation type
    /// @param sampling the interpolation sampling
    void AddInterpolationDecorations(uint32_t id,
                                     core::InterpolationType type,
                                     core::InterpolationSampling sampling);

    /// Generates the enabling of an extension. Emits an error and returns false if the extension is
    /// not supported.
    /// @param ext the extension to generate
    /// @returns true on success.
    bool GenerateExtension(wgsl::Extension ext);
    /// Generates a label for the given id. Emits an error and returns false if
    /// we're currently outside a function.
    /// @param id the id to use for the label
    /// @returns true on success.
    bool GenerateLabel(uint32_t id);
    /// Generates an assignment statement
    /// @param assign the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateAssignStatement(const ast::AssignmentStatement* assign);
    /// Generates a block statement, wrapped in a push/pop scope
    /// @param stmt the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateBlockStatement(const ast::BlockStatement* stmt);
    /// Generates a block statement
    /// @param stmt the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateBlockStatementWithoutScoping(const ast::BlockStatement* stmt);
    /// Generates a break statement
    /// @param stmt the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateBreakStatement(const ast::BreakStatement* stmt);
    /// Generates a break-if statement
    /// @param stmt the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateBreakIfStatement(const ast::BreakIfStatement* stmt);
    /// Generates a continue statement
    /// @param stmt the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateContinueStatement(const ast::ContinueStatement* stmt);
    /// Generates a discard statement
    /// @param stmt the statement to generate
    /// @returns true if the statement was successfully generated
    bool GenerateDiscardStatement(const ast::DiscardStatement* stmt);
    /// Generates an entry point instruction
    /// @param func the function
    /// @param id the id of the function
    /// @returns true if the instruction was generated, false otherwise
    bool GenerateEntryPoint(const ast::Function* func, uint32_t id);
    /// Generates execution modes for an entry point
    /// @param func the function
    /// @param id the id of the function
    /// @returns false on failure
    bool GenerateExecutionModes(const ast::Function* func, uint32_t id);
    /// Generates an expression
    /// @param expr the expression to generate
    /// @returns the resulting ID of the expression or 0 on error
    uint32_t GenerateExpression(const sem::Expression* expr);
    /// Generates an expression
    /// @param expr the expression to generate
    /// @returns the resulting ID of the expression or 0 on error
    uint32_t GenerateExpression(const ast::Expression* expr);
    /// Generates the instructions for a function
    /// @param func the function to generate
    /// @returns true if the instructions were generated
    bool GenerateFunction(const ast::Function* func);
    /// Generates a function type if not already created
    /// @param func the function to generate for
    /// @returns the ID to use for the function type. Returns 0 on failure.
    uint32_t GenerateFunctionTypeIfNeeded(const sem::Function* func);
    /// Generates access control annotations if needed
    /// @param type the type to generate for
    /// @param struct_id the struct id
    /// @param member_idx the member index
    void GenerateMemberAccessIfNeeded(const core::type::Type* type,
                                      uint32_t struct_id,
                                      uint32_t member_idx);
    /// Generates a function variable
    /// @param var the variable
    /// @returns true if the variable was generated
    bool GenerateFunctionVariable(const ast::Variable* var);
    /// Generates a global variable
    /// @param var the variable to generate
    /// @returns true if the variable is emited.
    bool GenerateGlobalVariable(const ast::Variable* var);
    /// Generates an index accessor expression.
    ///
    /// For more information on accessors see the "Pointer evaluation" section of
    /// the WGSL specification.
    ///
    /// @param expr the expression to generate
    /// @returns the id of the expression or 0 on failure
    uint32_t GenerateAccessorExpression(const ast::AccessorExpression* expr);
    /// Generates an index accessor
    /// @param expr the accessor to generate
    /// @param info the current accessor information
    /// @returns true if the accessor was generated successfully
    bool GenerateIndexAccessor(const ast::IndexAccessorExpression* expr, AccessorInfo* info);
    /// Generates a member accessor
    /// @param expr the accessor to generate
    /// @param info the current accessor information
    /// @returns true if the accessor was generated successfully
    bool GenerateMemberAccessor(const ast::MemberAccessorExpression* expr, AccessorInfo* info);
    /// Generates an identifier expression
    /// @param expr the expression to generate
    /// @returns the id of the expression or 0 on failure
    uint32_t GenerateIdentifierExpression(const ast::IdentifierExpression* expr);
    /// Generates a unary op expression
    /// @param expr the expression to generate
    /// @returns the id of the expression or 0 on failure
    uint32_t GenerateUnaryOpExpression(const ast::UnaryOpExpression* expr);
    /// Generates an if statement
    /// @param stmt the statement to generate
    /// @returns true on success
    bool GenerateIfStatement(const ast::IfStatement* stmt);
    /// Generates an import instruction for the "GLSL.std.450" extended
    /// instruction set, if one doesn't exist yet, and returns the import ID.
    /// @returns the import ID, or 0 on error.
    uint32_t GetGLSLstd450Import();
    /// Generates a constructor expression
    /// @param var the variable generated for, nullptr if no variable associated.
    /// @param expr the expression to generate
    /// @returns the ID of the expression or 0 on failure.
    uint32_t GenerateConstructorExpression(const ast::Variable* var, const ast::Expression* expr);
    /// Generates a literal constant if needed
    /// @param lit the literal to generate
    /// @returns the ID on success or 0 on failure
    uint32_t GenerateLiteralIfNeeded(const ast::LiteralExpression* lit);
    /// Generates a binary expression
    /// @param expr the expression to generate
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateBinaryExpression(const ast::BinaryExpression* expr);
    /// Generates a bitcast expression
    /// @param expr the expression to generate
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateBitcastExpression(const ast::BitcastExpression* expr);
    /// Generates a short circuting binary expression
    /// @param expr the expression to generate
    /// @returns teh expression ID on success or 0 otherwise
    uint32_t GenerateShortCircuitBinaryExpression(const ast::BinaryExpression* expr);
    /// Generates a call expression
    /// @param expr the expression to generate
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateCallExpression(const ast::CallExpression* expr);
    /// Handles generating a function call expression
    /// @param call the call expression
    /// @param function the function being called
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateFunctionCall(const sem::Call* call, const sem::Function* function);
    /// Handles generating a builtin call expression
    /// @param call the call expression
    /// @param builtin the builtin being called
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateBuiltinCall(const sem::Call* call, const sem::BuiltinFn* builtin);
    /// Handles generating a value constructor or value conversion expression
    /// @param call the call expression
    /// @param var the variable that is being initialized. May be null.
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateValueConstructorOrConversion(const sem::Call* call, const ast::Variable* var);
    /// Generates a texture builtin call. Emits an error and returns false if
    /// we're currently outside a function.
    /// @param call the call expression
    /// @param builtin the semantic information for the texture builtin
    /// @param result_type result type operand of the texture instruction
    /// @param result_id result identifier operand of the texture instruction
    /// parameters
    /// @returns true on success
    bool GenerateTextureBuiltin(const sem::Call* call,
                                const sem::BuiltinFn* builtin,
                                Operand result_type,
                                Operand result_id);
    /// Generates a control barrier statement.
    /// @param builtin the semantic information for the barrier builtin call
    /// @returns true on success
    bool GenerateControlBarrierBuiltin(const sem::BuiltinFn* builtin);
    /// Generates an atomic builtin call.
    /// @param call the call expression
    /// @param builtin the semantic information for the atomic builtin call
    /// @param result_type result type operand of the texture instruction
    /// @param result_id result identifier operand of the texture instruction
    /// @returns true on success
    bool GenerateAtomicBuiltin(const sem::Call* call,
                               const sem::BuiltinFn* builtin,
                               Operand result_type,
                               Operand result_id);
    /// Generates a sampled image
    /// @param texture_type the texture type
    /// @param texture_operand the texture operand
    /// @param sampler_operand the sampler operand
    /// @returns the expression ID
    uint32_t GenerateSampledImage(const core::type::Type* texture_type,
                                  Operand texture_operand,
                                  Operand sampler_operand);
    /// Generates a cast or object copy for the expression result,
    /// or return the ID generated the expression if it is already
    /// of the right type.
    /// @param to_type the type we're casting too
    /// @param from_expr the expression to cast
    /// @param is_global_init if this is a global initializer
    /// @returns the expression ID on success or 0 otherwise
    uint32_t GenerateCastOrCopyOrPassthrough(const core::type::Type* to_type,
                                             const ast::Expression* from_expr,
                                             bool is_global_init);
    /// Generates a loop statement
    /// @param stmt the statement to generate
    /// @returns true on successful generation
    bool GenerateLoopStatement(const ast::LoopStatement* stmt);
    /// Generates a return statement
    /// @param stmt the statement to generate
    /// @returns true on success, false otherwise
    bool GenerateReturnStatement(const ast::ReturnStatement* stmt);
    /// Generates a switch statement
    /// @param stmt the statement to generate
    /// @returns ture on success, false otherwise
    bool GenerateSwitchStatement(const ast::SwitchStatement* stmt);
    /// Generates a conditional section merge block
    /// @param cond the condition
    /// @param true_body the statements making up the true block
    /// @param else_stmt the statement for the else block
    /// @returns true on success, false on failure
    bool GenerateConditionalBlock(const ast::Expression* cond,
                                  const ast::BlockStatement* true_body,
                                  const ast::Statement* else_stmt);
    /// Generates a statement
    /// @param stmt the statement to generate
    /// @returns true if the statement was generated
    bool GenerateStatement(const ast::Statement* stmt);
    /// Generates an OpLoad of the given expression type
    /// @param type the reference type of the expression
    /// @param id the SPIR-V id of the expression
    /// @returns the ID of the loaded value or 0 on failure.
    uint32_t GenerateLoad(const core::type::Reference* type, uint32_t id);
    /// Generates an OpLoad on the given ID if it has reference type in WGSL, otherwise return the
    /// ID itself.
    /// @param type the type of the expression
    /// @param id the SPIR-V id of the expression
    /// @returns the ID of the loaded value or `id` if type is not a reference
    uint32_t GenerateLoadIfNeeded(const core::type::Type* type, uint32_t id);
    /// Generates an OpStore. Emits an error and returns false if we're
    /// currently outside a function.
    /// @param to the ID to store too
    /// @param from the ID to store from
    /// @returns true on success
    bool GenerateStore(uint32_t to, uint32_t from);
    /// Generates a type if not already created
    /// @param type the type to create
    /// @returns the ID to use for the given type. Returns 0 on unknown type.
    uint32_t GenerateTypeIfNeeded(const core::type::Type* type);
    /// Generates a texture type declaration
    /// @param texture the texture to generate
    /// @param result the result operand
    /// @returns true if the texture was successfully generated
    bool GenerateTextureType(const core::type::Texture* texture, const Operand& result);
    /// Generates an array type declaration
    /// @param ary the array to generate
    /// @param result the result operand
    /// @returns true if the array was successfully generated
    bool GenerateArrayType(const core::type::Array* ary, const Operand& result);
    /// Generates a matrix type declaration
    /// @param mat the matrix to generate
    /// @param result the result operand
    /// @returns true if the matrix was successfully generated
    bool GenerateMatrixType(const core::type::Matrix* mat, const Operand& result);
    /// Generates a pointer type declaration
    /// @param ptr the pointer type to generate
    /// @param result the result operand
    /// @returns true if the pointer was successfully generated
    bool GeneratePointerType(const core::type::Pointer* ptr, const Operand& result);
    /// Generates a reference type declaration
    /// @param ref the reference type to generate
    /// @param result the result operand
    /// @returns true if the reference was successfully generated
    bool GenerateReferenceType(const core::type::Reference* ref, const Operand& result);
    /// Generates a vector type declaration
    /// @param struct_type the vector to generate
    /// @param result the result operand
    /// @returns true if the vector was successfully generated
    bool GenerateStructType(const core::type::Struct* struct_type, const Operand& result);
    /// Generates a struct member
    /// @param struct_id the id of the parent structure
    /// @param idx the index of the member
    /// @param member the member to generate
    /// @returns the id of the struct member or 0 on error.
    uint32_t GenerateStructMember(uint32_t struct_id,
                                  uint32_t idx,
                                  const core::type::StructMember* member);
    /// Generates a variable declaration statement
    /// @param stmt the statement to generate
    /// @returns true on successfull generation
    bool GenerateVariableDeclStatement(const ast::VariableDeclStatement* stmt);
    /// Generates a vector type declaration
    /// @param vec the vector to generate
    /// @param result the result operand
    /// @returns true if the vector was successfully generated
    bool GenerateVectorType(const core::type::Vector* vec, const Operand& result);

    /// Generates instructions to splat `scalar_id` into a vector of type
    /// `vec_type`
    /// @param scalar_id scalar to splat
    /// @param vec_type type of vector
    /// @returns id of the new vector
    uint32_t GenerateSplat(uint32_t scalar_id, const core::type::Type* vec_type);

    /// Generates instructions to add or subtract two matrices
    /// @param lhs_id id of multiplicand
    /// @param rhs_id id of multiplier
    /// @param type type of both matrices and of result
    /// @param op one of `spv::Op::OpFAdd` or `spv::Op::OpFSub`
    /// @returns id of the result matrix
    uint32_t GenerateMatrixAddOrSub(uint32_t lhs_id,
                                    uint32_t rhs_id,
                                    const core::type::Matrix* type,
                                    spv::Op op);

    /// Converts TexelFormat to SPIR-V and pushes an appropriate capability.
    /// @param format AST image format type
    /// @returns SPIR-V image format type
    SpvImageFormat convert_texel_format_to_spv(const core::TexelFormat format);

    /// Determines if the given value constructor is created from constant values
    /// @param expr the expression to check
    /// @returns true if the constructor is constant
    bool IsConstructorConst(const ast::CallExpression* expr);

  private:
    /// @returns an Operand with a new result ID in it. Increments the next_id_
    /// automatically.
    Operand result_op();

    /// @returns the resolved type of the ast::Expression `expr`
    /// @param expr the expression
    const core::type::Type* TypeOf(const ast::Expression* expr) const {
        return builder_.TypeOf(expr);
    }

    /// Generates a constant value if needed
    /// @param constant the constant to generate.
    /// @returns the ID on success or 0 on failure
    uint32_t GenerateConstantIfNeeded(const core::constant::Value* constant);

    /// Generates a scalar constant if needed
    /// @param constant the constant to generate.
    /// @returns the ID on success or 0 on failure
    uint32_t GenerateConstantIfNeeded(const ScalarConstant& constant);

    /// Generates a constant-null of the given type, if needed
    /// @param type the type of the constant null to generate.
    /// @returns the ID on success or 0 on failure
    uint32_t GenerateConstantNullIfNeeded(const core::type::Type* type);

    /// Generates a vector constant splat if needed
    /// @param type the type of the vector to generate
    /// @param value_id the ID of the scalar value to splat
    /// @returns the ID on success or 0 on failure
    uint32_t GenerateConstantVectorSplatIfNeeded(const core::type::Vector* type, uint32_t value_id);

    /// Registers the semantic variable to the given SPIR-V ID
    /// @param var the semantic variable
    /// @param id the generated SPIR-V identifier for the variable
    void RegisterVariable(const sem::Variable* var, uint32_t id);

    /// Looks up the SPIR-V ID for the variable, which must have been registered
    /// with a call to RegisterVariable()
    /// @returns the SPIR-V ID, or 0 if the variable was not found
    uint32_t LookupVariableID(const sem::Variable* var);

    /// Pushes a new scope
    void PushScope();

    /// Pops the top-most scope
    void PopScope();

    /// Declare all the extensions and capabilities required by `OpSDot` and `OpUDot` using 4x8
    // packed integer vectors as input.
    void DeclarePacked4x8IntegerDotProductCapabilitiesAndExtensions();

    ProgramBuilder builder_;
    writer::Module module_;
    Function current_function_;
    uint32_t current_label_id_ = 0;

    // Scope holds per-block information
    struct Scope {
        Scope();
        Scope(const Scope&);
        ~Scope();
        std::unordered_map<OperandListKey, uint32_t> type_init_to_id_;
    };

    std::unordered_map<const sem::Variable*, uint32_t> var_to_id_;
    std::unordered_map<uint32_t, const sem::Variable*> id_to_var_;
    std::unordered_map<std::string, uint32_t> import_name_to_id_;
    std::unordered_map<Symbol, uint32_t> func_symbol_to_id_;
    std::unordered_map<sem::CallTargetSignature, uint32_t> func_sig_to_id_;
    std::unordered_map<const core::type::Type*, uint32_t> type_to_id_;
    std::unordered_map<ScalarConstant, uint32_t> const_to_id_;
    std::unordered_map<const core::type::Type*, uint32_t> const_null_to_id_;
    std::unordered_map<uint64_t, uint32_t> const_splat_to_id_;
    std::unordered_map<const core::type::Type*, uint32_t> texture_type_to_sampled_image_type_id_;
    std::vector<Scope> scope_stack_;
    std::vector<uint32_t> merge_stack_;
    std::vector<uint32_t> continue_stack_;
    bool zero_initialize_workgroup_memory_ = false;
    bool experimental_require_subgroup_uniform_control_flow_ = false;

    struct ContinuingInfo {
        ContinuingInfo(const ast::Statement* last_statement,
                       uint32_t loop_header_id,
                       uint32_t break_target_id);
        // The last statement in the continiung block.
        const ast::Statement* const last_statement = nullptr;
        // The ID of the loop header
        const uint32_t loop_header_id = 0u;
        // The ID of the merge block for the loop.
        const uint32_t break_target_id = 0u;
    };
    // Stack of nodes, where each is the last statement in a surrounding
    // continuing block.
    std::vector<ContinuingInfo> continuing_stack_;

    // The instruction to emit as the backedge of a loop.
    struct Backedge {
        Backedge(spv::Op, OperandList);
        Backedge(const Backedge&);
        Backedge& operator=(const Backedge&);
        ~Backedge();

        spv::Op opcode;
        OperandList operands;
    };
    std::vector<Backedge> backedge_stack_;
};

}  // namespace tint::spirv::writer

#endif  // SRC_TINT_LANG_SPIRV_WRITER_AST_PRINTER_BUILDER_H_