transform: Reimplement FirstIndexOffset

* It didn't always produce valid WGSL (crbug.com/tint/687)
* It didn't handle builtins as entry point parameters
* It used hard-coded symbols that could collide
* It didn't use DataMap for input.

The new implementation addresses all of this.

Bug: tint:687
Change-Id: I447bec530b45414ebb8baeb4ee18261d73d1c0d2
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/47222
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
diff --git a/src/program_builder.h b/src/program_builder.h
index 6c728cc..5fddb56 100644
--- a/src/program_builder.h
+++ b/src/program_builder.h
@@ -445,9 +445,10 @@
     /// @param name the alias name
     /// @param type the alias type
     /// @returns the alias pointer
-    type::Alias* alias(const std::string& name, type::Type* type) const {
-      return builder->create<type::Alias>(builder->Symbols().Register(name),
-                                          type);
+    template <typename NAME>
+    type::Alias* alias(NAME&& name, type::Type* type) const {
+      return builder->create<type::Alias>(
+          builder->Sym(std::forward<NAME>(name)), type);
     }
 
     /// @return the tint AST pointer to `type` with the given ast::StorageClass
@@ -469,9 +470,10 @@
     /// @param name the struct name
     /// @param impl the struct implementation
     /// @returns a struct pointer
-    type::Struct* struct_(const std::string& name, ast::Struct* impl) const {
-      return builder->create<type::Struct>(builder->Symbols().Register(name),
-                                           impl);
+    template <typename NAME>
+    type::Struct* struct_(NAME&& name, ast::Struct* impl) const {
+      return builder->create<type::Struct>(
+          builder->Sym(std::forward<NAME>(name)), impl);
     }
 
    private:
@@ -1075,13 +1077,14 @@
   /// @param members the struct members
   /// @param decorations the optional struct decorations
   /// @returns the struct type
+  template <typename NAME>
   type::Struct* Structure(const Source& source,
-                          const std::string& name,
+                          NAME&& name,
                           ast::StructMemberList members,
                           ast::DecorationList decorations = {}) {
     auto* impl =
         create<ast::Struct>(source, std::move(members), std::move(decorations));
-    auto* type = ty.struct_(name, impl);
+    auto* type = ty.struct_(Sym(std::forward<NAME>(name)), impl);
     AST().AddConstructedType(type);
     return type;
   }
@@ -1092,12 +1095,13 @@
   /// @param members the struct members
   /// @param decorations the optional struct decorations
   /// @returns the struct type
-  type::Struct* Structure(const std::string& name,
+  template <typename NAME>
+  type::Struct* Structure(NAME&& name,
                           ast::StructMemberList members,
                           ast::DecorationList decorations = {}) {
     auto* impl =
         create<ast::Struct>(std::move(members), std::move(decorations));
-    auto* type = ty.struct_(name, impl);
+    auto* type = ty.struct_(Sym(std::forward<NAME>(name)), impl);
     AST().AddConstructedType(type);
     return type;
   }
diff --git a/src/transform/first_index_offset.cc b/src/transform/first_index_offset.cc
index 3766e01..a1adf66 100644
--- a/src/transform/first_index_offset.cc
+++ b/src/transform/first_index_offset.cc
@@ -15,40 +15,34 @@
 #include "src/transform/first_index_offset.h"
 
 #include <memory>
+#include <unordered_map>
 #include <utility>
 
 #include "src/ast/struct_block_decoration.h"
 #include "src/program_builder.h"
 #include "src/semantic/function.h"
+#include "src/semantic/member_accessor_expression.h"
+#include "src/semantic/struct.h"
+#include "src/semantic/variable.h"
 
+TINT_INSTANTIATE_TYPEINFO(tint::transform::FirstIndexOffset::BindingPoint);
 TINT_INSTANTIATE_TYPEINFO(tint::transform::FirstIndexOffset::Data);
 
 namespace tint {
 namespace transform {
 namespace {
 
-constexpr char kStructName[] = "TintFirstIndexOffsetData";
-constexpr char kBufferName[] = "tint_first_index_data";
-constexpr char kFirstVertexName[] = "tint_first_vertex_index";
-constexpr char kFirstInstanceName[] = "tint_first_instance_index";
-constexpr char kIndexOffsetPrefix[] = "tint_first_index_offset_";
-
-ast::Variable* clone_variable_with_new_name(CloneContext* ctx,
-                                            ast::Variable* in,
-                                            std::string new_name) {
-  // Clone arguments outside of create() call to have deterministic ordering
-  auto source = ctx->Clone(in->source());
-  auto symbol = ctx->dst->Symbols().Register(new_name);
-  auto* type = ctx->Clone(in->declared_type());
-  auto* constructor = ctx->Clone(in->constructor());
-  auto decorations = ctx->Clone(in->decorations());
-  return ctx->dst->create<ast::Variable>(
-      source, symbol, in->declared_storage_class(), type, in->is_const(),
-      constructor, decorations);
-}
+// Uniform buffer member names
+constexpr char kFirstVertexName[] = "first_vertex_index";
+constexpr char kFirstInstanceName[] = "first_instance_index";
 
 }  // namespace
 
+FirstIndexOffset::BindingPoint::BindingPoint() = default;
+FirstIndexOffset::BindingPoint::BindingPoint(uint32_t b, uint32_t g)
+    : binding(b), group(g) {}
+FirstIndexOffset::BindingPoint::~BindingPoint() = default;
+
 FirstIndexOffset::Data::Data(bool has_vtx_index,
                              bool has_inst_index,
                              uint32_t first_vtx_offset,
@@ -57,172 +51,134 @@
       has_instance_index(has_inst_index),
       first_vertex_offset(first_vtx_offset),
       first_instance_offset(first_inst_offset) {}
-
 FirstIndexOffset::Data::Data(const Data&) = default;
-
 FirstIndexOffset::Data::~Data() = default;
 
+FirstIndexOffset::FirstIndexOffset() = default;
 FirstIndexOffset::FirstIndexOffset(uint32_t binding, uint32_t group)
     : binding_(binding), group_(group) {}
 
 FirstIndexOffset::~FirstIndexOffset() = default;
 
-Transform::Output FirstIndexOffset::Run(const Program* in, const DataMap&) {
-  ProgramBuilder out;
-
-  // First do a quick check to see if the transform has already been applied.
-  for (ast::Variable* var : in->AST().GlobalVariables()) {
-    if (auto* dec_var = var->As<ast::Variable>()) {
-      if (dec_var->symbol() == in->Symbols().Get(kBufferName)) {
-        out.Diagnostics().add_error(
-            "First index offset transform has already been applied.");
-        return Output(Program(std::move(out)));
-      }
-    }
+Transform::Output FirstIndexOffset::Run(const Program* in,
+                                        const DataMap& data) {
+  // Get the uniform buffer binding point
+  uint32_t ub_binding = binding_;
+  uint32_t ub_group = group_;
+  if (auto* binding_point = data.Get<BindingPoint>()) {
+    ub_binding = binding_point->binding;
+    ub_group = binding_point->group;
   }
 
-  State state{&out, binding_, group_};
-
-  Symbol vertex_index_sym;
-  Symbol instance_index_sym;
-
-  // Lazily construct the UniformBuffer on first call to
-  // maybe_create_buffer_var()
-  ast::Variable* buffer_var = nullptr;
-  auto maybe_create_buffer_var = [&]() {
-    if (buffer_var == nullptr) {
-      buffer_var = state.AddUniformBuffer();
-    }
-  };
-
-  // Clone the AST, renaming the kVertexIndex and kInstanceIndex builtins, and
-  // add a CreateFirstIndexOffset() statement to each function that uses one of
-  // these builtins.
-
+  ProgramBuilder out;
   CloneContext ctx(&out, in);
-  ctx.ReplaceAll([&](ast::Variable* var) -> ast::Variable* {
-    for (ast::Decoration* dec : var->decorations()) {
-      if (auto* blt_dec = dec->As<ast::BuiltinDecoration>()) {
-        ast::Builtin blt_type = blt_dec->value();
-        if (blt_type == ast::Builtin::kVertexIndex) {
-          vertex_index_sym = var->symbol();
-          state.has_vertex_index = true;
-          return clone_variable_with_new_name(
-              &ctx, var,
-              kIndexOffsetPrefix + in->Symbols().NameFor(var->symbol()));
-        } else if (blt_type == ast::Builtin::kInstanceIndex) {
-          instance_index_sym = var->symbol();
-          state.has_instance_index = true;
-          return clone_variable_with_new_name(
-              &ctx, var,
-              kIndexOffsetPrefix + in->Symbols().NameFor(var->symbol()));
-        }
-      }
-    }
-    return nullptr;  // Just clone var
-  });
-  ctx.ReplaceAll(  // Note: This happens in the same pass as the rename above
-                   // which determines the original builtin variable names,
-                   // but this should be fine, as variables are cloned first.
-      [&](ast::Function* func) -> ast::Function* {
-        maybe_create_buffer_var();
-        if (buffer_var == nullptr) {
-          return nullptr;  // no transform need, just clone func
-        }
-        auto* func_sem = in->Sem().Get(func);
-        ast::StatementList statements;
-        for (const auto& data : func_sem->LocalReferencedBuiltinVariables()) {
-          if (data.second->value() == ast::Builtin::kVertexIndex) {
-            statements.emplace_back(state.CreateFirstIndexOffset(
-                in->Symbols().NameFor(vertex_index_sym), kFirstVertexName,
-                buffer_var));
-          } else if (data.second->value() == ast::Builtin::kInstanceIndex) {
-            statements.emplace_back(state.CreateFirstIndexOffset(
-                in->Symbols().NameFor(instance_index_sym), kFirstInstanceName,
-                buffer_var));
+
+  // Map of builtin usages
+  std::unordered_map<const semantic::Variable*, const char*> builtin_vars;
+  std::unordered_map<const semantic::StructMember*, const char*>
+      builtin_members;
+
+  bool has_vertex_index = false;
+  bool has_instance_index = false;
+
+  // Traverse the AST scanning for builtin accesses via variables (includes
+  // parameters) or structure member accesses.
+  for (auto* node : in->ASTNodes().Objects()) {
+    if (auto* var = node->As<ast::Variable>()) {
+      for (ast::Decoration* dec : var->decorations()) {
+        if (auto* builtin_dec = dec->As<ast::BuiltinDecoration>()) {
+          ast::Builtin builtin = builtin_dec->value();
+          if (builtin == ast::Builtin::kVertexIndex) {
+            auto* sem_var = ctx.src->Sem().Get(var);
+            builtin_vars.emplace(sem_var, kFirstVertexName);
+            has_vertex_index = true;
+          }
+          if (builtin == ast::Builtin::kInstanceIndex) {
+            auto* sem_var = ctx.src->Sem().Get(var);
+            builtin_vars.emplace(sem_var, kFirstInstanceName);
+            has_instance_index = true;
           }
         }
-        return CloneWithStatementsAtStart(&ctx, func, statements);
-      });
+      }
+    }
+    if (auto* member = node->As<ast::StructMember>()) {
+      for (ast::Decoration* dec : member->decorations()) {
+        if (auto* builtin_dec = dec->As<ast::BuiltinDecoration>()) {
+          ast::Builtin builtin = builtin_dec->value();
+          if (builtin == ast::Builtin::kVertexIndex) {
+            auto* sem_mem = ctx.src->Sem().Get(member);
+            builtin_members.emplace(sem_mem, kFirstVertexName);
+            has_vertex_index = true;
+          }
+          if (builtin == ast::Builtin::kInstanceIndex) {
+            auto* sem_mem = ctx.src->Sem().Get(member);
+            builtin_members.emplace(sem_mem, kFirstInstanceName);
+            has_instance_index = true;
+          }
+        }
+      }
+    }
+  }
+
+  // Byte offsets on the uniform buffer
+  uint32_t vertex_index_offset = 0;
+  uint32_t instance_index_offset = 0;
+
+  if (has_vertex_index || has_instance_index) {
+    // Add uniform buffer members and calculate byte offsets
+    uint32_t offset = 0;
+    ast::StructMemberList members;
+    if (has_vertex_index) {
+      members.push_back(ctx.dst->Member(kFirstVertexName, ctx.dst->ty.u32()));
+      vertex_index_offset = offset;
+      offset += 4;
+    }
+    if (has_instance_index) {
+      members.push_back(ctx.dst->Member(kFirstInstanceName, ctx.dst->ty.u32()));
+      instance_index_offset = offset;
+      offset += 4;
+    }
+    auto* struct_type =
+        ctx.dst->Structure(ctx.dst->Symbols().New(), std::move(members),
+                           {ctx.dst->create<ast::StructBlockDecoration>()});
+
+    // Create a global to hold the uniform buffer
+    Symbol buffer_name = ctx.dst->Symbols().New();
+    ctx.dst->Global(buffer_name, struct_type, ast::StorageClass::kUniform,
+                    nullptr,
+                    ast::DecorationList{
+                        ctx.dst->create<ast::BindingDecoration>(ub_binding),
+                        ctx.dst->create<ast::GroupDecoration>(ub_group),
+                    });
+
+    // Fix up all references to the builtins with the offsets
+    ctx.ReplaceAll([=, &ctx](ast::Expression* expr) -> ast::Expression* {
+      auto* sem = ctx.src->Sem().Get(expr);
+      if (auto* user = sem->As<semantic::VariableUser>()) {
+        auto it = builtin_vars.find(user->Variable());
+        if (it != builtin_vars.end()) {
+          return ctx.dst->Add(ctx.CloneWithoutTransform(expr),
+                              ctx.dst->MemberAccessor(buffer_name, it->second));
+        }
+      }
+      if (auto* access = sem->As<semantic::StructMemberAccess>()) {
+        auto it = builtin_members.find(access->Member());
+        if (it != builtin_members.end()) {
+          return ctx.dst->Add(ctx.CloneWithoutTransform(expr),
+                              ctx.dst->MemberAccessor(buffer_name, it->second));
+        }
+      }
+      // Not interested in this experssion. Just clone.
+      return nullptr;
+    });
+  }
+
   ctx.Clone();
 
-  return Output(Program(std::move(out)),
-                std::make_unique<Data>(
-                    state.has_vertex_index, state.has_instance_index,
-                    state.vertex_index_offset, state.instance_index_offset));
-}
-
-ast::Variable* FirstIndexOffset::State::AddUniformBuffer() {
-  auto* u32_type = dst->create<type::U32>();
-  uint32_t offset = 0;
-  ast::StructMemberList members;
-  if (has_vertex_index) {
-    members.push_back(dst->create<ast::StructMember>(
-        Source{}, dst->Symbols().Register(kFirstVertexName), u32_type,
-        ast::DecorationList{}));
-    vertex_index_offset = offset;
-    offset += 4;
-  }
-
-  if (has_instance_index) {
-    members.push_back(dst->create<ast::StructMember>(
-        Source{}, dst->Symbols().Register(kFirstInstanceName), u32_type,
-        ast::DecorationList{}));
-    instance_index_offset = offset;
-    offset += 4;
-  }
-
-  ast::DecorationList decos;
-  decos.push_back(dst->create<ast::StructBlockDecoration>(Source{}));
-
-  auto* struct_type = dst->create<type::Struct>(
-      dst->Symbols().Register(kStructName),
-      dst->create<ast::Struct>(Source{}, std::move(members), std::move(decos)));
-
-  auto* idx_var = dst->create<ast::Variable>(
-      Source{},                              // source
-      dst->Symbols().Register(kBufferName),  // symbol
-      ast::StorageClass::kUniform,           // storage_class
-      struct_type,                           // type
-      false,                                 // is_const
-      nullptr,                               // constructor
-      ast::DecorationList{
-          dst->create<ast::BindingDecoration>(Source{}, binding),
-          dst->create<ast::GroupDecoration>(Source{}, group),
-      });
-
-  dst->AST().AddConstructedType(struct_type);
-
-  dst->AST().AddGlobalVariable(idx_var);
-
-  return idx_var;
-}
-
-ast::VariableDeclStatement* FirstIndexOffset::State::CreateFirstIndexOffset(
-    const std::string& original_name,
-    const std::string& field_name,
-    ast::Variable* buffer_var) {
-  auto* buffer =
-      dst->create<ast::IdentifierExpression>(Source{}, buffer_var->symbol());
-
-  auto lhs_name = kIndexOffsetPrefix + original_name;
-  auto* constructor = dst->create<ast::BinaryExpression>(
-      Source{}, ast::BinaryOp::kAdd,
-      dst->create<ast::IdentifierExpression>(Source{},
-                                             dst->Symbols().Register(lhs_name)),
-      dst->create<ast::MemberAccessorExpression>(
-          Source{}, buffer,
-          dst->create<ast::IdentifierExpression>(
-              Source{}, dst->Symbols().Register(field_name))));
-  auto* var = dst->create<ast::Variable>(
-      Source{},                                // source
-      dst->Symbols().Register(original_name),  // symbol
-      ast::StorageClass::kNone,                // storage_class
-      dst->create<type::U32>(),                // type
-      true,                                    // is_const
-      constructor,                             // constructor
-      ast::DecorationList{});                  // decorations
-  return dst->create<ast::VariableDeclStatement>(Source{}, var);
+  return Output(
+      Program(std::move(out)),
+      std::make_unique<Data>(has_vertex_index, has_instance_index,
+                             vertex_index_offset, instance_index_offset));
 }
 
 }  // namespace transform
diff --git a/src/transform/first_index_offset.h b/src/transform/first_index_offset.h
index ed092fb..7f819bc 100644
--- a/src/transform/first_index_offset.h
+++ b/src/transform/first_index_offset.h
@@ -15,9 +15,6 @@
 #ifndef SRC_TRANSFORM_FIRST_INDEX_OFFSET_H_
 #define SRC_TRANSFORM_FIRST_INDEX_OFFSET_H_
 
-#include <string>
-
-#include "src/ast/variable_decl_statement.h"
 #include "src/transform/transform.h"
 
 namespace tint {
@@ -60,6 +57,27 @@
 ///
 class FirstIndexOffset : public Transform {
  public:
+  /// BindingPoint is consumed by the FirstIndexOffset transform.
+  /// BindingPoint specifies the binding point of the first index uniform
+  /// buffer.
+  struct BindingPoint : public Castable<BindingPoint, transform::Data> {
+    /// Constructor
+    BindingPoint();
+
+    /// Constructor
+    /// @param b the binding index
+    /// @param g the binding group
+    BindingPoint(uint32_t b, uint32_t g);
+
+    /// Destructor
+    ~BindingPoint() override;
+
+    /// [[binding()]] for the first vertex / first instance uniform buffer
+    uint32_t binding = 0;
+    /// [[group()]] for the first vertex / first instance uniform buffer
+    uint32_t group = 0;
+  };
+
   /// Data is outputted by the FirstIndexOffset transform.
   /// Data holds information about shader usage and constant buffer offsets.
   struct Data : public Castable<Data, transform::Data> {
@@ -90,6 +108,9 @@
   };
 
   /// Constructor
+  FirstIndexOffset();
+  /// Constructor
+  /// [DEPRECATED] - pass BindingPoint as part of the `data` to Run()
   /// @param binding the binding() for firstVertex/Instance uniform
   /// @param group the group() for firstVertex/Instance uniform
   FirstIndexOffset(uint32_t binding, uint32_t group);
@@ -102,32 +123,10 @@
   Output Run(const Program* program, const DataMap& data = {}) override;
 
  private:
-  struct State {
-    /// Adds uniform buffer with firstVertex/Instance to the program builder
-    /// @returns variable of new uniform buffer
-    ast::Variable* AddUniformBuffer();
-    /// Adds constant with modified original_name builtin to func
-    /// @param original_name the name of the original builtin used in function
-    /// @param field_name name of field in firstVertex/Instance buffer
-    /// @param buffer_var variable of firstVertex/Instance buffer
-    ast::VariableDeclStatement* CreateFirstIndexOffset(
-        const std::string& original_name,
-        const std::string& field_name,
-        ast::Variable* buffer_var);
-
-    ProgramBuilder* const dst;
-    uint32_t const binding;
-    uint32_t const group;
-
-    bool has_vertex_index = false;
-    bool has_instance_index = false;
-    uint32_t vertex_index_offset = 0;
-    uint32_t instance_index_offset = 0;
-  };
-
-  uint32_t binding_;
-  uint32_t group_;
+  uint32_t binding_ = 0;
+  uint32_t group_ = 0;
 };
+
 }  // namespace transform
 }  // namespace tint
 
diff --git a/src/transform/first_index_offset_test.cc b/src/transform/first_index_offset_test.cc
index ccfecf9..2a9b075 100644
--- a/src/transform/first_index_offset_test.cc
+++ b/src/transform/first_index_offset_test.cc
@@ -26,45 +26,13 @@
 
 using FirstIndexOffsetTest = TransformTest;
 
-TEST_F(FirstIndexOffsetTest, Error_AlreadyTransformed) {
-  auto* src = R"(
-[[builtin(vertex_index)]] var<in> vert_idx : u32;
-
-fn test() -> u32 {
-  return vert_idx;
-}
-
-[[stage(vertex)]]
-fn entry() {
-  test();
-}
-)";
-
-  auto* expect =
-      "error: First index offset transform has already been applied.";
-
-  std::vector<std::unique_ptr<transform::Transform>> transforms;
-  transforms.emplace_back(std::make_unique<FirstIndexOffset>(0, 0));
-  transforms.emplace_back(std::make_unique<FirstIndexOffset>(1, 1));
-
-  auto got = Run(src, std::move(transforms));
-
-  EXPECT_EQ(expect, str(got));
-
-  auto* data = got.data.Get<FirstIndexOffset::Data>();
-
-  ASSERT_NE(data, nullptr);
-  EXPECT_EQ(data->has_vertex_index, true);
-  EXPECT_EQ(data->has_instance_index, false);
-  EXPECT_EQ(data->first_vertex_offset, 0u);
-  EXPECT_EQ(data->first_instance_offset, 0u);
-}
-
 TEST_F(FirstIndexOffsetTest, EmptyModule) {
   auto* src = "";
   auto* expect = "";
 
-  auto got = Run(src, std::make_unique<FirstIndexOffset>(0, 0));
+  DataMap config;
+  config.Add<FirstIndexOffset::BindingPoint>(0, 0);
+  auto got = Run<FirstIndexOffset>(src, std::move(config));
 
   EXPECT_EQ(expect, str(got));
 
@@ -79,6 +47,273 @@
 
 TEST_F(FirstIndexOffsetTest, BasicModuleVertexIndex) {
   auto* src = R"(
+fn test(vert_idx : u32) -> u32 {
+  return vert_idx;
+}
+
+[[stage(vertex)]]
+fn entry([[builtin(vertex_index)]] vert_idx : u32) {
+  test(vert_idx);
+}
+)";
+
+  auto* expect = R"(
+[[block]]
+struct tint_symbol_2 {
+  first_vertex_index : u32;
+};
+
+[[binding(1), group(2)]] var<uniform> tint_symbol_3 : tint_symbol_2;
+
+fn test(vert_idx : u32) -> u32 {
+  return vert_idx;
+}
+
+[[stage(vertex)]]
+fn entry([[builtin(vertex_index)]] vert_idx : u32) {
+  test((vert_idx + tint_symbol_3.first_vertex_index));
+}
+)";
+
+  DataMap config;
+  config.Add<FirstIndexOffset::BindingPoint>(1, 2);
+  auto got = Run<FirstIndexOffset>(src, std::move(config));
+
+  EXPECT_EQ(expect, str(got));
+
+  auto* data = got.data.Get<FirstIndexOffset::Data>();
+
+  ASSERT_NE(data, nullptr);
+  EXPECT_EQ(data->has_vertex_index, true);
+  EXPECT_EQ(data->has_instance_index, false);
+  EXPECT_EQ(data->first_vertex_offset, 0u);
+  EXPECT_EQ(data->first_instance_offset, 0u);
+}
+
+TEST_F(FirstIndexOffsetTest, BasicModuleInstanceIndex) {
+  auto* src = R"(
+fn test(inst_idx : u32) -> u32 {
+  return inst_idx;
+}
+
+[[stage(vertex)]]
+fn entry([[builtin(instance_index)]] inst_idx : u32) {
+  test(inst_idx);
+}
+)";
+
+  auto* expect = R"(
+[[block]]
+struct tint_symbol_2 {
+  first_instance_index : u32;
+};
+
+[[binding(1), group(7)]] var<uniform> tint_symbol_3 : tint_symbol_2;
+
+fn test(inst_idx : u32) -> u32 {
+  return inst_idx;
+}
+
+[[stage(vertex)]]
+fn entry([[builtin(instance_index)]] inst_idx : u32) {
+  test((inst_idx + tint_symbol_3.first_instance_index));
+}
+)";
+
+  DataMap config;
+  config.Add<FirstIndexOffset::BindingPoint>(1, 7);
+  auto got = Run<FirstIndexOffset>(src, std::move(config));
+
+  EXPECT_EQ(expect, str(got));
+
+  auto* data = got.data.Get<FirstIndexOffset::Data>();
+
+  ASSERT_NE(data, nullptr);
+  EXPECT_EQ(data->has_vertex_index, false);
+  EXPECT_EQ(data->has_instance_index, true);
+  EXPECT_EQ(data->first_vertex_offset, 0u);
+  EXPECT_EQ(data->first_instance_offset, 0u);
+}
+
+TEST_F(FirstIndexOffsetTest, BasicModuleBothIndex) {
+  auto* src = R"(
+fn test(instance_idx : u32, vert_idx : u32) -> u32 {
+  return instance_idx + vert_idx;
+}
+
+struct Inputs {
+  [[builtin(instance_index)]] instance_idx : u32;
+  [[builtin(vertex_index)]] vert_idx : u32;
+};
+
+[[stage(vertex)]]
+fn entry(inputs : Inputs) {
+  test(inputs.instance_idx, inputs.vert_idx);
+}
+)";
+
+  auto* expect = R"(
+[[block]]
+struct tint_symbol_3 {
+  first_vertex_index : u32;
+  first_instance_index : u32;
+};
+
+[[binding(1), group(2)]] var<uniform> tint_symbol_4 : tint_symbol_3;
+
+fn test(instance_idx : u32, vert_idx : u32) -> u32 {
+  return (instance_idx + vert_idx);
+}
+
+struct Inputs {
+  [[builtin(instance_index)]]
+  instance_idx : u32;
+  [[builtin(vertex_index)]]
+  vert_idx : u32;
+};
+
+[[stage(vertex)]]
+fn entry(inputs : Inputs) {
+  test((inputs.instance_idx + tint_symbol_4.first_instance_index), (inputs.vert_idx + tint_symbol_4.first_vertex_index));
+}
+)";
+
+  DataMap config;
+  config.Add<FirstIndexOffset::BindingPoint>(1, 2);
+  auto got = Run<FirstIndexOffset>(src, std::move(config));
+
+  EXPECT_EQ(expect, str(got));
+
+  auto* data = got.data.Get<FirstIndexOffset::Data>();
+
+  ASSERT_NE(data, nullptr);
+  EXPECT_EQ(data->has_vertex_index, true);
+  EXPECT_EQ(data->has_instance_index, true);
+  EXPECT_EQ(data->first_vertex_offset, 0u);
+  EXPECT_EQ(data->first_instance_offset, 4u);
+}
+
+TEST_F(FirstIndexOffsetTest, NestedCalls) {
+  auto* src = R"(
+fn func1(vert_idx : u32) -> u32 {
+  return vert_idx;
+}
+
+fn func2(vert_idx : u32) -> u32 {
+  return func1(vert_idx);
+}
+
+[[stage(vertex)]]
+fn entry([[builtin(vertex_index)]] vert_idx : u32) {
+  func2(vert_idx);
+}
+)";
+
+  auto* expect = R"(
+[[block]]
+struct tint_symbol_2 {
+  first_vertex_index : u32;
+};
+
+[[binding(1), group(2)]] var<uniform> tint_symbol_3 : tint_symbol_2;
+
+fn func1(vert_idx : u32) -> u32 {
+  return vert_idx;
+}
+
+fn func2(vert_idx : u32) -> u32 {
+  return func1(vert_idx);
+}
+
+[[stage(vertex)]]
+fn entry([[builtin(vertex_index)]] vert_idx : u32) {
+  func2((vert_idx + tint_symbol_3.first_vertex_index));
+}
+)";
+
+  DataMap config;
+  config.Add<FirstIndexOffset::BindingPoint>(1, 2);
+  auto got = Run<FirstIndexOffset>(src, std::move(config));
+
+  EXPECT_EQ(expect, str(got));
+
+  auto* data = got.data.Get<FirstIndexOffset::Data>();
+
+  ASSERT_NE(data, nullptr);
+  EXPECT_EQ(data->has_vertex_index, true);
+  EXPECT_EQ(data->has_instance_index, false);
+  EXPECT_EQ(data->first_vertex_offset, 0u);
+  EXPECT_EQ(data->first_instance_offset, 0u);
+}
+
+TEST_F(FirstIndexOffsetTest, MultipleEntryPoints) {
+  auto* src = R"(
+fn func(i : u32) -> u32 {
+  return i;
+}
+
+[[stage(vertex)]]
+fn entry_a([[builtin(vertex_index)]] vert_idx : u32) {
+  func(vert_idx);
+}
+
+[[stage(vertex)]]
+fn entry_b([[builtin(vertex_index)]] vert_idx : u32, [[builtin(instance_index)]] inst_idx : u32) {
+  func(vert_idx + inst_idx);
+}
+
+[[stage(vertex)]]
+fn entry_c([[builtin(instance_index)]] inst_idx : u32) {
+  func(inst_idx);
+}
+)";
+
+  auto* expect = R"(
+[[block]]
+struct tint_symbol_3 {
+  first_vertex_index : u32;
+  first_instance_index : u32;
+};
+
+[[binding(1), group(2)]] var<uniform> tint_symbol_4 : tint_symbol_3;
+
+fn func(i : u32) -> u32 {
+  return i;
+}
+
+[[stage(vertex)]]
+fn entry_a([[builtin(vertex_index)]] vert_idx : u32) {
+  func((vert_idx + tint_symbol_4.first_vertex_index));
+}
+
+[[stage(vertex)]]
+fn entry_b([[builtin(vertex_index)]] vert_idx : u32, [[builtin(instance_index)]] inst_idx : u32) {
+  func(((vert_idx + tint_symbol_4.first_vertex_index) + (inst_idx + tint_symbol_4.first_instance_index)));
+}
+
+[[stage(vertex)]]
+fn entry_c([[builtin(instance_index)]] inst_idx : u32) {
+  func((inst_idx + tint_symbol_4.first_instance_index));
+}
+)";
+
+  DataMap config;
+  config.Add<FirstIndexOffset::BindingPoint>(1, 2);
+  auto got = Run<FirstIndexOffset>(src, std::move(config));
+
+  EXPECT_EQ(expect, str(got));
+
+  auto* data = got.data.Get<FirstIndexOffset::Data>();
+
+  ASSERT_NE(data, nullptr);
+  EXPECT_EQ(data->has_vertex_index, true);
+  EXPECT_EQ(data->has_instance_index, true);
+  EXPECT_EQ(data->first_vertex_offset, 0u);
+  EXPECT_EQ(data->first_instance_offset, 4u);
+}
+
+TEST_F(FirstIndexOffsetTest, OLD_BasicModuleVertexIndex) {
+  auto* src = R"(
 [[builtin(vertex_index)]] var<in> vert_idx : u32;
 
 fn test() -> u32 {
@@ -93,17 +328,16 @@
 
   auto* expect = R"(
 [[block]]
-struct TintFirstIndexOffsetData {
-  tint_first_vertex_index : u32;
+struct tint_symbol_2 {
+  first_vertex_index : u32;
 };
 
-[[binding(1), group(2)]] var<uniform> tint_first_index_data : TintFirstIndexOffsetData;
+[[binding(1), group(2)]] var<uniform> tint_symbol_3 : tint_symbol_2;
 
-[[builtin(vertex_index)]] var<in> tint_first_index_offset_vert_idx : u32;
+[[builtin(vertex_index)]] var<in> vert_idx : u32;
 
 fn test() -> u32 {
-  let vert_idx : u32 = (tint_first_index_offset_vert_idx + tint_first_index_data.tint_first_vertex_index);
-  return vert_idx;
+  return (vert_idx + tint_symbol_3.first_vertex_index);
 }
 
 [[stage(vertex)]]
@@ -125,7 +359,7 @@
   EXPECT_EQ(data->first_instance_offset, 0u);
 }
 
-TEST_F(FirstIndexOffsetTest, BasicModuleInstanceIndex) {
+TEST_F(FirstIndexOffsetTest, OLD_BasicModuleInstanceIndex) {
   auto* src = R"(
 [[builtin(instance_index)]] var<in> inst_idx : u32;
 
@@ -141,17 +375,16 @@
 
   auto* expect = R"(
 [[block]]
-struct TintFirstIndexOffsetData {
-  tint_first_instance_index : u32;
+struct tint_symbol_2 {
+  first_instance_index : u32;
 };
 
-[[binding(1), group(7)]] var<uniform> tint_first_index_data : TintFirstIndexOffsetData;
+[[binding(1), group(7)]] var<uniform> tint_symbol_3 : tint_symbol_2;
 
-[[builtin(instance_index)]] var<in> tint_first_index_offset_inst_idx : u32;
+[[builtin(instance_index)]] var<in> inst_idx : u32;
 
 fn test() -> u32 {
-  let inst_idx : u32 = (tint_first_index_offset_inst_idx + tint_first_index_data.tint_first_instance_index);
-  return inst_idx;
+  return (inst_idx + tint_symbol_3.first_instance_index);
 }
 
 [[stage(vertex)]]
@@ -173,7 +406,7 @@
   EXPECT_EQ(data->first_instance_offset, 0u);
 }
 
-TEST_F(FirstIndexOffsetTest, BasicModuleBothIndex) {
+TEST_F(FirstIndexOffsetTest, OLD_BasicModuleBothIndex) {
   auto* src = R"(
 [[builtin(instance_index)]] var<in> instance_idx : u32;
 [[builtin(vertex_index)]] var<in> vert_idx : u32;
@@ -190,21 +423,19 @@
 
   auto* expect = R"(
 [[block]]
-struct TintFirstIndexOffsetData {
-  tint_first_vertex_index : u32;
-  tint_first_instance_index : u32;
+struct tint_symbol_3 {
+  first_vertex_index : u32;
+  first_instance_index : u32;
 };
 
-[[binding(1), group(2)]] var<uniform> tint_first_index_data : TintFirstIndexOffsetData;
+[[binding(1), group(2)]] var<uniform> tint_symbol_4 : tint_symbol_3;
 
-[[builtin(instance_index)]] var<in> tint_first_index_offset_instance_idx : u32;
+[[builtin(instance_index)]] var<in> instance_idx : u32;
 
-[[builtin(vertex_index)]] var<in> tint_first_index_offset_vert_idx : u32;
+[[builtin(vertex_index)]] var<in> vert_idx : u32;
 
 fn test() -> u32 {
-  let instance_idx : u32 = (tint_first_index_offset_instance_idx + tint_first_index_data.tint_first_instance_index);
-  let vert_idx : u32 = (tint_first_index_offset_vert_idx + tint_first_index_data.tint_first_vertex_index);
-  return (instance_idx + vert_idx);
+  return ((instance_idx + tint_symbol_4.first_instance_index) + (vert_idx + tint_symbol_4.first_vertex_index));
 }
 
 [[stage(vertex)]]
@@ -226,7 +457,7 @@
   EXPECT_EQ(data->first_instance_offset, 4u);
 }
 
-TEST_F(FirstIndexOffsetTest, NestedCalls) {
+TEST_F(FirstIndexOffsetTest, OLD_NestedCalls) {
   auto* src = R"(
 [[builtin(vertex_index)]] var<in> vert_idx : u32;
 
@@ -246,17 +477,16 @@
 
   auto* expect = R"(
 [[block]]
-struct TintFirstIndexOffsetData {
-  tint_first_vertex_index : u32;
+struct tint_symbol_2 {
+  first_vertex_index : u32;
 };
 
-[[binding(1), group(2)]] var<uniform> tint_first_index_data : TintFirstIndexOffsetData;
+[[binding(1), group(2)]] var<uniform> tint_symbol_3 : tint_symbol_2;
 
-[[builtin(vertex_index)]] var<in> tint_first_index_offset_vert_idx : u32;
+[[builtin(vertex_index)]] var<in> vert_idx : u32;
 
 fn func1() -> u32 {
-  let vert_idx : u32 = (tint_first_index_offset_vert_idx + tint_first_index_data.tint_first_vertex_index);
-  return vert_idx;
+  return (vert_idx + tint_symbol_3.first_vertex_index);
 }
 
 fn func2() -> u32 {