transform: Make methods const, add ShouldRun()

Transforms are supposed to be immutable, operating on the DataMaps provided for input and output, so make the methods const.

Add a ShouldRun() method which the Manager can use to skip over transforms that do not need to be run.

Change-Id: I320ac964577e94ac988748d8aca85bd43ee8d3b5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/77120
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/reader/spirv/parser.cc

@@ -52,7 +52,7 @@ Program Parse(const std::vector<uint32_t>& input) {
 
   // If the generated program contains matrices with a custom MatrixStride
   // attribute then we need to decompose these into an array of vectors
-  if (transform::DecomposeStridedMatrix::ShouldRun(&program)) {
+  if (transform::DecomposeStridedMatrix().ShouldRun(&program)) {
     transform::Manager manager;
     manager.Add<transform::Unshadow>();
     manager.Add<transform::SimplifyPointers>();

src/transform/add_empty_entry_point.cc

@@ -27,7 +27,9 @@ AddEmptyEntryPoint::AddEmptyEntryPoint() = default;
 
 AddEmptyEntryPoint::~AddEmptyEntryPoint() = default;
 
-void AddEmptyEntryPoint::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void AddEmptyEntryPoint::Run(CloneContext& ctx,
+                             const DataMap&,
+                             DataMap&) const {
   for (auto* func : ctx.src->AST().Functions()) {
     if (func->IsEntryPoint()) {
       ctx.Clone();

src/transform/add_empty_entry_point.h

@@ -35,7 +35,9 @@ class AddEmptyEntryPoint : public Castable<AddEmptyEntryPoint, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/add_spirv_block_decoration.cc

@@ -33,7 +33,9 @@ AddSpirvBlockDecoration::AddSpirvBlockDecoration() = default;
 
 AddSpirvBlockDecoration::~AddSpirvBlockDecoration() = default;
 
-void AddSpirvBlockDecoration::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void AddSpirvBlockDecoration::Run(CloneContext& ctx,
+                                  const DataMap&,
+                                  DataMap&) const {
   auto& sem = ctx.src->Sem();
 
   // Collect the set of structs that are nested in other types.

src/transform/add_spirv_block_decoration.h

@@ -65,7 +65,9 @@ class AddSpirvBlockDecoration
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/array_length_from_uniform.cc

@@ -95,7 +95,7 @@ static void IterateArrayLengthOnStorageVar(CloneContext& ctx, F&& functor) {
 
 void ArrayLengthFromUniform::Run(CloneContext& ctx,
                                  const DataMap& inputs,
-                                 DataMap& outputs) {
+                                 DataMap& outputs) const {
   if (!Requires<SimplifyPointers>(ctx)) {
     return;
   }

src/transform/array_length_from_uniform.h

@@ -103,7 +103,9 @@ class ArrayLengthFromUniform
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/binding_remapper.cc

@@ -42,7 +42,9 @@ BindingRemapper::Remappings::~Remappings() = default;
 BindingRemapper::BindingRemapper() = default;
 BindingRemapper::~BindingRemapper() = default;
 
-void BindingRemapper::Run(CloneContext& ctx, const DataMap& inputs, DataMap&) {
+void BindingRemapper::Run(CloneContext& ctx,
+                          const DataMap& inputs,
+                          DataMap&) const {
   auto* remappings = inputs.Get<Remappings>();
   if (!remappings) {
     ctx.dst->Diagnostics().add_error(

src/transform/binding_remapper.h

@@ -75,7 +75,9 @@ class BindingRemapper : public Castable<BindingRemapper, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/calculate_array_length.cc

@@ -71,7 +71,9 @@ CalculateArrayLength::BufferSizeIntrinsic::Clone(CloneContext* ctx) const {
 CalculateArrayLength::CalculateArrayLength() = default;
 CalculateArrayLength::~CalculateArrayLength() = default;
 
-void CalculateArrayLength::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void CalculateArrayLength::Run(CloneContext& ctx,
+                               const DataMap&,
+                               DataMap&) const {
   auto& sem = ctx.src->Sem();
   if (!Requires<SimplifyPointers>(ctx)) {
     return;

src/transform/calculate_array_length.h

@@ -63,7 +63,9 @@ class CalculateArrayLength : public Castable<CalculateArrayLength, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/canonicalize_entry_point_io.cc

@@ -550,7 +550,7 @@ struct CanonicalizeEntryPointIO::State {
 
 void CanonicalizeEntryPointIO::Run(CloneContext& ctx,
                                    const DataMap& inputs,
-                                   DataMap&) {
+                                   DataMap&) const {
   if (!Requires<Unshadow>(ctx)) {
     return;
   }

src/transform/canonicalize_entry_point_io.h

@@ -131,7 +131,9 @@ class CanonicalizeEntryPointIO
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
   struct State;
 };

src/transform/combine_samplers.cc

@@ -304,7 +304,9 @@ CombineSamplers::CombineSamplers() = default;
 
 CombineSamplers::~CombineSamplers() = default;
 
-void CombineSamplers::Run(CloneContext& ctx, const DataMap& inputs, DataMap&) {
+void CombineSamplers::Run(CloneContext& ctx,
+                          const DataMap& inputs,
+                          DataMap&) const {
   auto* binding_info = inputs.Get<BindingInfo>();
   if (!binding_info) {
     ctx.dst->Diagnostics().add_error(

src/transform/combine_samplers.h

@@ -95,7 +95,9 @@ class CombineSamplers : public Castable<CombineSamplers, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/decompose_memory_access.cc

@@ -790,7 +790,9 @@ const DecomposeMemoryAccess::Intrinsic* DecomposeMemoryAccess::Intrinsic::Clone(
 DecomposeMemoryAccess::DecomposeMemoryAccess() = default;
 DecomposeMemoryAccess::~DecomposeMemoryAccess() = default;
 
-void DecomposeMemoryAccess::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void DecomposeMemoryAccess::Run(CloneContext& ctx,
+                                const DataMap&,
+                                DataMap&) const {
   auto& sem = ctx.src->Sem();
 
   State state(ctx);

src/transform/decompose_memory_access.h

@@ -112,7 +112,9 @@ class DecomposeMemoryAccess
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
   struct State;
 };

src/transform/decompose_strided_matrix.cc

@@ -107,7 +107,7 @@ DecomposeStridedMatrix::DecomposeStridedMatrix() = default;
 
 DecomposeStridedMatrix::~DecomposeStridedMatrix() = default;
 
-bool DecomposeStridedMatrix::ShouldRun(const Program* program) {
+bool DecomposeStridedMatrix::ShouldRun(const Program* program) const {
   bool should_run = false;
   GatherCustomStrideMatrixMembers(
       program, [&](const sem::StructMember*, sem::Matrix*, uint32_t) {
@@ -117,7 +117,9 @@ bool DecomposeStridedMatrix::ShouldRun(const Program* program) {
   return should_run;
 }
 
-void DecomposeStridedMatrix::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void DecomposeStridedMatrix::Run(CloneContext& ctx,
+                                 const DataMap&,
+                                 DataMap&) const {
   if (!Requires<SimplifyPointers>(ctx)) {
     return;
   }

src/transform/decompose_strided_matrix.h

@@ -36,7 +36,7 @@ class DecomposeStridedMatrix
 
   /// @param program the program to inspect
   /// @returns true if this transform should be run for the given program
-  static bool ShouldRun(const Program* program);
+  bool ShouldRun(const Program* program) const override;
 
  protected:
   /// Runs the transform using the CloneContext built for transforming a
@@ -45,7 +45,9 @@ class DecomposeStridedMatrix
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/decompose_strided_matrix_test.cc

@@ -41,11 +41,45 @@ TEST_F(DecomposeStridedMatrixTest, Empty) {
 }
 
 TEST_F(DecomposeStridedMatrixTest, MissingDependencySimplify) {
-  auto* src = R"()";
+  // struct S {
+  //   [[offset(16), stride(32)]]
+  //   [[internal(ignore_stride_decoration)]]
+  //   m : mat2x2<f32>;
+  // };
+  // [[group(0), binding(0)]] var<uniform> s : S;
+  //
+  // [[stage(compute), workgroup_size(1)]]
+  // fn f() {
+  //   let x : mat2x2<f32> = s.m;
+  // }
+  ProgramBuilder b;
+  auto* S = b.Structure(
+      "S",
+      {
+          b.Member(
+              "m", b.ty.mat2x2<f32>(),
+              {
+                  b.create<ast::StructMemberOffsetDecoration>(16),
+                  b.create<ast::StrideDecoration>(32),
+                  b.Disable(ast::DisabledValidation::kIgnoreStrideDecoration),
+              }),
+      });
+  b.Global("s", b.ty.Of(S), ast::StorageClass::kUniform,
+           b.GroupAndBinding(0, 0));
+  b.Func(
+      "f", {}, b.ty.void_(),
+      {
+          b.Decl(b.Const("x", b.ty.mat2x2<f32>(), b.MemberAccessor("s", "m"))),
+      },
+      {
+          b.Stage(ast::PipelineStage::kCompute),
+          b.WorkgroupSize(1),
+      });
+
   auto* expect =
       R"(error: tint::transform::DecomposeStridedMatrix depends on tint::transform::SimplifyPointers but the dependency was not run)";
 
-  auto got = Run<DecomposeStridedMatrix>(src);
+  auto got = Run<DecomposeStridedMatrix>(Program(std::move(b)));
 
   EXPECT_EQ(expect, str(got));
 }

src/transform/external_texture_transform.cc

@@ -28,7 +28,7 @@ ExternalTextureTransform::~ExternalTextureTransform() = default;
 
 void ExternalTextureTransform::Run(CloneContext& ctx,
                                    const DataMap&,
-                                   DataMap&) {
+                                   DataMap&) const {
   auto& sem = ctx.src->Sem();
 
   // Within this transform, usages of texture_external are replaced with a

src/transform/external_texture_transform.h

@@ -42,7 +42,9 @@ class ExternalTextureTransform
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/first_index_offset.cc

@@ -59,7 +59,7 @@ FirstIndexOffset::~FirstIndexOffset() = default;
 
 void FirstIndexOffset::Run(CloneContext& ctx,
                            const DataMap& inputs,
-                           DataMap& outputs) {
+                           DataMap& outputs) const {
   // Get the uniform buffer binding point
   uint32_t ub_binding = binding_;
   uint32_t ub_group = group_;

src/transform/first_index_offset.h

@@ -122,7 +122,9 @@ class FirstIndexOffset : public Castable<FirstIndexOffset, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   uint32_t binding_ = 0;

src/transform/fold_constants.cc

@@ -33,7 +33,7 @@ FoldConstants::FoldConstants() = default;
 
 FoldConstants::~FoldConstants() = default;
 
-void FoldConstants::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void FoldConstants::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   ctx.ReplaceAll([&](const ast::Expression* expr) -> const ast::Expression* {
     auto* call = ctx.src->Sem().Get<sem::Call>(expr);
     if (!call) {

src/transform/fold_constants.h

@@ -36,7 +36,9 @@ class FoldConstants : public Castable<FoldConstants, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/fold_trivial_single_use_lets.cc

@@ -51,7 +51,7 @@ FoldTrivialSingleUseLets::~FoldTrivialSingleUseLets() = default;
 
 void FoldTrivialSingleUseLets::Run(CloneContext& ctx,
                                    const DataMap&,
-                                   DataMap&) {
+                                   DataMap&) const {
   for (auto* node : ctx.src->ASTNodes().Objects()) {
     if (auto* block = node->As<ast::BlockStatement>()) {
       auto& stmts = block->statements;

src/transform/fold_trivial_single_use_lets.h

@@ -50,7 +50,9 @@ class FoldTrivialSingleUseLets
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/for_loop_to_loop.cc

@@ -25,7 +25,7 @@ ForLoopToLoop::ForLoopToLoop() = default;
 
 ForLoopToLoop::~ForLoopToLoop() = default;
 
-void ForLoopToLoop::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void ForLoopToLoop::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   ctx.ReplaceAll(
       [&](const ast::ForLoopStatement* for_loop) -> const ast::Statement* {
         ast::StatementList stmts;

src/transform/for_loop_to_loop.h

@@ -37,7 +37,9 @@ class ForLoopToLoop : public Castable<ForLoopToLoop, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/glsl.cc

@@ -45,7 +45,7 @@ namespace transform {
 Glsl::Glsl() = default;
 Glsl::~Glsl() = default;
 
-Output Glsl::Run(const Program* in, const DataMap& inputs) {
+Output Glsl::Run(const Program* in, const DataMap& inputs) const {
   Manager manager;
   DataMap data;
 

src/transform/glsl.h

@@ -61,7 +61,7 @@ class Glsl : public Castable<Glsl, Transform> {
   /// @param program the source program to transform
   /// @param data optional extra transform-specific data
   /// @returns the transformation result
-  Output Run(const Program* program, const DataMap& data = {}) override;
+  Output Run(const Program* program, const DataMap& data = {}) const override;
 };
 
 }  // namespace transform

src/transform/localize_struct_array_assignment.cc

@@ -215,7 +215,7 @@ LocalizeStructArrayAssignment::~LocalizeStructArrayAssignment() = default;
 
 void LocalizeStructArrayAssignment::Run(CloneContext& ctx,
                                         const DataMap&,
-                                        DataMap&) {
+                                        DataMap&) const {
   if (!Requires<SimplifyPointers>(ctx)) {
     return;
   }

src/transform/localize_struct_array_assignment.h

@@ -41,7 +41,9 @@ class LocalizeStructArrayAssignment
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   class State;

src/transform/loop_to_for_loop.cc

@@ -56,7 +56,7 @@ LoopToForLoop::LoopToForLoop() = default;
 
 LoopToForLoop::~LoopToForLoop() = default;
 
-void LoopToForLoop::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void LoopToForLoop::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   ctx.ReplaceAll([&](const ast::LoopStatement* loop) -> const ast::Statement* {
     // For loop condition is taken from the first statement in the loop.
     // This requires an if-statement with either:

src/transform/loop_to_for_loop.h

@@ -37,7 +37,9 @@ class LoopToForLoop : public Castable<LoopToForLoop, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/manager.cc

@@ -32,7 +32,7 @@ namespace transform {
 Manager::Manager() = default;
 Manager::~Manager() = default;
 
-Output Manager::Run(const Program* program, const DataMap& data) {
+Output Manager::Run(const Program* program, const DataMap& data) const {
 #if TINT_PRINT_PROGRAM_FOR_EACH_TRANSFORM
   auto print_program = [&](const char* msg, const Transform* transform) {
     auto wgsl = Program::printer(program);
@@ -49,16 +49,22 @@ Output Manager::Run(const Program* program, const DataMap& data) {
   };
 #endif
 
+  const Program* in = program;
+
   Output out;
-  if (!transforms_.empty()) {
   for (const auto& transform : transforms_) {
+    if (!transform->ShouldRun(in)) {
+      TINT_IF_PRINT_PROGRAM(std::cout << "Skipping "
+                                      << transform->TypeInfo().name);
+      continue;
+    }
     TINT_IF_PRINT_PROGRAM(print_program("Input to", transform.get()));
 
-      auto res = transform->Run(program, data);
+    auto res = transform->Run(in, data);
     out.program = std::move(res.program);
     out.data.Add(std::move(res.data));
-      program = &out.program;
+    in = &out.program;
-      if (!program->IsValid()) {
+    if (!in->IsValid()) {
       TINT_IF_PRINT_PROGRAM(
           print_program("Invalid output of", transform.get()));
       return out;
@@ -68,7 +74,8 @@ Output Manager::Run(const Program* program, const DataMap& data) {
       TINT_IF_PRINT_PROGRAM(print_program("Output of", transform.get()));
     }
   }
-  } else {
+
+  if (program == in) {
     out.program = program->Clone();
   }
 

src/transform/manager.h

@@ -52,7 +52,7 @@ class Manager : public Castable<Manager, Transform> {
   /// @param program the source program to transform
   /// @param data optional extra transform-specific input data
   /// @returns the transformed program and diagnostics
-  Output Run(const Program* program, const DataMap& data = {}) override;
+  Output Run(const Program* program, const DataMap& data = {}) const override;
 
  private:
   std::vector<std::unique_ptr<Transform>> transforms_;

src/transform/module_scope_var_to_entry_point_param.cc

@@ -379,7 +379,7 @@ ModuleScopeVarToEntryPointParam::~ModuleScopeVarToEntryPointParam() = default;
 
 void ModuleScopeVarToEntryPointParam::Run(CloneContext& ctx,
                                           const DataMap&,
-                                          DataMap&) {
+                                          DataMap&) const {
   State state{ctx};
   state.Process();
   ctx.Clone();

src/transform/module_scope_var_to_entry_point_param.h

@@ -77,7 +77,9 @@ class ModuleScopeVarToEntryPointParam
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
   struct State;
 };

src/transform/multiplanar_external_texture.cc

@@ -413,10 +413,10 @@ MultiplanarExternalTexture::~MultiplanarExternalTexture() = default;
 // parameters. Calls to textureLoad or textureSampleLevel that contain a
 // texture_external parameter will be transformed into a newly generated version
 // of the function, which can perform the desired operation on a single RGBA
-// plane or on seperate Y and UV planes.
+// plane or on separate Y and UV planes.
 void MultiplanarExternalTexture::Run(CloneContext& ctx,
                                      const DataMap& inputs,
-                                     DataMap&) {
+                                     DataMap&) const {
   auto* new_binding_points = inputs.Get<NewBindingPoints>();
 
   if (!new_binding_points) {

src/transform/multiplanar_external_texture.h

@@ -85,7 +85,9 @@ class MultiplanarExternalTexture
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/num_workgroups_from_uniform.cc

@@ -54,7 +54,7 @@ NumWorkgroupsFromUniform::~NumWorkgroupsFromUniform() = default;
 
 void NumWorkgroupsFromUniform::Run(CloneContext& ctx,
                                    const DataMap& inputs,
-                                   DataMap&) {
+                                   DataMap&) const {
   if (!Requires<CanonicalizeEntryPointIO>(ctx)) {
     return;
   }

src/transform/num_workgroups_from_uniform.h

@@ -70,7 +70,9 @@ class NumWorkgroupsFromUniform
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/pad_array_elements.cc

@@ -97,7 +97,7 @@ PadArrayElements::PadArrayElements() = default;
 
 PadArrayElements::~PadArrayElements() = default;
 
-void PadArrayElements::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void PadArrayElements::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   auto& sem = ctx.src->Sem();
 
   std::unordered_map<const sem::Array*, ArrayBuilder> padded_arrays;

src/transform/pad_array_elements.h

@@ -45,7 +45,9 @@ class PadArrayElements : public Castable<PadArrayElements, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/promote_side_effects_to_decl.cc

@@ -398,7 +398,7 @@ PromoteSideEffectsToDecl::~PromoteSideEffectsToDecl() = default;
 
 void PromoteSideEffectsToDecl::Run(CloneContext& ctx,
                                    const DataMap& inputs,
-                                   DataMap&) {
+                                   DataMap&) const {
   auto* cfg = inputs.Get<Config>();
   if (cfg == nullptr) {
     ctx.dst->Diagnostics().add_error(

src/transform/promote_side_effects_to_decl.h

@@ -61,7 +61,9 @@ class PromoteSideEffectsToDecl
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   class State;

src/transform/remove_phonies.cc

@@ -68,7 +68,7 @@ RemovePhonies::RemovePhonies() = default;
 
 RemovePhonies::~RemovePhonies() = default;
 
-void RemovePhonies::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void RemovePhonies::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   auto& sem = ctx.src->Sem();
 
   std::unordered_map<SinkSignature, Symbol, SinkSignature::Hasher> sinks;

src/transform/remove_phonies.h

@@ -41,7 +41,9 @@ class RemovePhonies : public Castable<RemovePhonies, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/remove_unreachable_statements.cc

@@ -39,7 +39,7 @@ RemoveUnreachableStatements::~RemoveUnreachableStatements() = default;
 
 void RemoveUnreachableStatements::Run(CloneContext& ctx,
                                       const DataMap&,
-                                      DataMap&) {
+                                      DataMap&) const {
   for (auto* node : ctx.src->ASTNodes().Objects()) {
     if (auto* stmt = ctx.src->Sem().Get<sem::Statement>(node)) {
       if (!stmt->IsReachable()) {

src/transform/remove_unreachable_statements.h

@@ -41,7 +41,9 @@ class RemoveUnreachableStatements
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/renamer.cc

@@ -1252,7 +1252,7 @@ Renamer::Config::~Config() = default;
 Renamer::Renamer() = default;
 Renamer::~Renamer() = default;
 
-Output Renamer::Run(const Program* in, const DataMap& inputs) {
+Output Renamer::Run(const Program* in, const DataMap& inputs) const {
   ProgramBuilder out;
   // Disable auto-cloning of symbols, since we want to rename them.
   CloneContext ctx(&out, in, false);

src/transform/renamer.h

@@ -85,7 +85,7 @@ class Renamer : public Castable<Renamer, Transform> {
   /// @param program the source program to transform
   /// @param data optional extra transform-specific input data
   /// @returns the transformation result
-  Output Run(const Program* program, const DataMap& data = {}) override;
+  Output Run(const Program* program, const DataMap& data = {}) const override;
 };
 
 }  // namespace transform

src/transform/robustness.cc

@@ -293,7 +293,7 @@ Robustness::Config& Robustness::Config::operator=(const Config&) = default;
 Robustness::Robustness() = default;
 Robustness::~Robustness() = default;
 
-void Robustness::Run(CloneContext& ctx, const DataMap& inputs, DataMap&) {
+void Robustness::Run(CloneContext& ctx, const DataMap& inputs, DataMap&) const {
   Config cfg;
   if (auto* cfg_data = inputs.Get<Config>()) {
     cfg = *cfg_data;

src/transform/robustness.h

@@ -74,7 +74,9 @@ class Robustness : public Castable<Robustness, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   struct State;

src/transform/simplify_pointers.cc

@@ -231,7 +231,7 @@ SimplifyPointers::SimplifyPointers() = default;
 
 SimplifyPointers::~SimplifyPointers() = default;
 
-void SimplifyPointers::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void SimplifyPointers::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   if (!Requires<Unshadow>(ctx)) {
     return;
   }

src/transform/simplify_pointers.h

@@ -46,7 +46,9 @@ class SimplifyPointers : public Castable<SimplifyPointers, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/single_entry_point.cc

@@ -31,7 +31,9 @@ SingleEntryPoint::SingleEntryPoint() = default;
 
 SingleEntryPoint::~SingleEntryPoint() = default;
 
-void SingleEntryPoint::Run(CloneContext& ctx, const DataMap& inputs, DataMap&) {
+void SingleEntryPoint::Run(CloneContext& ctx,
+                           const DataMap& inputs,
+                           DataMap&) const {
   auto* cfg = inputs.Get<Config>();
   if (cfg == nullptr) {
     ctx.dst->Diagnostics().add_error(

src/transform/single_entry_point.h

@@ -61,7 +61,9 @@ class SingleEntryPoint : public Castable<SingleEntryPoint, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/transform.cc

@@ -46,7 +46,8 @@ Output::Output(Program&& p) : program(std::move(p)) {}
 Transform::Transform() = default;
 Transform::~Transform() = default;
 
-Output Transform::Run(const Program* program, const DataMap& data /* = {} */) {
+Output Transform::Run(const Program* program,
+                      const DataMap& data /* = {} */) const {
   ProgramBuilder builder;
   CloneContext ctx(&builder, program);
   Output output;
@@ -56,13 +57,18 @@ Output Transform::Run(const Program* program, const DataMap& data /* = {} */) {
   return output;
 }
 
-void Transform::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void Transform::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   TINT_UNIMPLEMENTED(Transform, ctx.dst->Diagnostics())
       << "Transform::Run() unimplemented for " << TypeInfo().name;
 }
 
-bool Transform::Requires(CloneContext& ctx,
+bool Transform::ShouldRun(const Program*) const {
-                         std::initializer_list<const ::tint::TypeInfo*> deps) {
+  return true;
+}
+
+bool Transform::Requires(
+    CloneContext& ctx,
+    std::initializer_list<const ::tint::TypeInfo*> deps) const {
   for (auto* dep : deps) {
     if (!ctx.src->HasTransformApplied(dep)) {
       ctx.dst->Diagnostics().add_error(

src/transform/transform.h

@@ -157,7 +157,11 @@ class Transform : public Castable<Transform> {
   /// @param program the source program to transform
   /// @param data optional extra transform-specific input data
   /// @returns the transformation result
-  virtual Output Run(const Program* program, const DataMap& data = {});
+  virtual Output Run(const Program* program, const DataMap& data = {}) const;
+
+  /// @param program the program to inspect
+  /// @returns true if this transform should be run for the given program
+  virtual bool ShouldRun(const Program* program) const;
 
  protected:
   /// Runs the transform using the CloneContext built for transforming a
@@ -166,14 +170,16 @@ class Transform : public Castable<Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  virtual void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs);
+  virtual void Run(CloneContext& ctx,
+                   const DataMap& inputs,
+                   DataMap& outputs) const;
 
   /// Requires appends an error diagnostic to `ctx.dst` if the template type
   /// transforms were not already run on `ctx.src`.
   /// @param ctx the CloneContext
   /// @returns true if all dependency transforms have been run
   template <typename... TRANSFORMS>
-  bool Requires(CloneContext& ctx) {
+  bool Requires(CloneContext& ctx) const {
     return Requires(ctx, {&::tint::TypeInfo::Of<TRANSFORMS>()...});
   }
 
@@ -183,7 +189,7 @@ class Transform : public Castable<Transform> {
   /// @param deps the list of Transform TypeInfos
   /// @returns true if all dependency transforms have been run
   bool Requires(CloneContext& ctx,
-                std::initializer_list<const ::tint::TypeInfo*> deps);
+                std::initializer_list<const ::tint::TypeInfo*> deps) const;
 
   /// Removes the statement `stmt` from the transformed program.
   /// RemoveStatement handles edge cases, like statements in the initializer and

src/transform/transform_test.cc

@@ -24,7 +24,7 @@ namespace {
 
 // Inherit from Transform so we have access to protected methods
 struct CreateASTTypeForTest : public testing::Test, public Transform {
-  Output Run(const Program*, const DataMap&) override { return {}; }
+  Output Run(const Program*, const DataMap&) const override { return {}; }
 
   const ast::Type* create(
       std::function<sem::Type*(ProgramBuilder&)> create_sem_type) {

src/transform/unshadow.cc

@@ -91,7 +91,7 @@ Unshadow::Unshadow() = default;
 
 Unshadow::~Unshadow() = default;
 
-void Unshadow::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void Unshadow::Run(CloneContext& ctx, const DataMap&, DataMap&) const {
   State(ctx).Run();
 }
 

src/transform/unshadow.h

@@ -39,7 +39,9 @@ class Unshadow : public Castable<Unshadow, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/vectorize_scalar_matrix_constructors.cc

@@ -34,7 +34,7 @@ VectorizeScalarMatrixConstructors::~VectorizeScalarMatrixConstructors() =
 
 void VectorizeScalarMatrixConstructors::Run(CloneContext& ctx,
                                             const DataMap&,
-                                            DataMap&) {
+                                            DataMap&) const {
   ctx.ReplaceAll(
       [&](const ast::CallExpression* expr) -> const ast::CallExpression* {
         auto* call = ctx.src->Sem().Get(expr);

src/transform/vectorize_scalar_matrix_constructors.h

@@ -37,7 +37,9 @@ class VectorizeScalarMatrixConstructors
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 };
 
 }  // namespace transform

src/transform/vertex_pulling.cc

@@ -903,7 +903,9 @@ struct State {
 VertexPulling::VertexPulling() = default;
 VertexPulling::~VertexPulling() = default;
 
-void VertexPulling::Run(CloneContext& ctx, const DataMap& inputs, DataMap&) {
+void VertexPulling::Run(CloneContext& ctx,
+                        const DataMap& inputs,
+                        DataMap&) const {
   auto cfg = cfg_;
   if (auto* cfg_data = inputs.Get<Config>()) {
     cfg = *cfg_data;

src/transform/vertex_pulling.h

@@ -172,7 +172,9 @@ class VertexPulling : public Castable<VertexPulling, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   Config cfg_;

src/transform/wrap_arrays_in_structs.cc

@@ -38,7 +38,9 @@ WrapArraysInStructs::WrapArraysInStructs() = default;
 
 WrapArraysInStructs::~WrapArraysInStructs() = default;
 
-void WrapArraysInStructs::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void WrapArraysInStructs::Run(CloneContext& ctx,
+                              const DataMap&,
+                              DataMap&) const {
   auto& sem = ctx.src->Sem();
 
   std::unordered_map<const sem::Array*, WrappedArrayInfo> wrapped_arrays;

src/transform/wrap_arrays_in_structs.h

@@ -51,7 +51,9 @@ class WrapArraysInStructs : public Castable<WrapArraysInStructs, Transform> {
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   struct WrappedArrayInfo {

src/transform/zero_init_workgroup_memory.cc

@@ -433,7 +433,9 @@ ZeroInitWorkgroupMemory::ZeroInitWorkgroupMemory() = default;
 
 ZeroInitWorkgroupMemory::~ZeroInitWorkgroupMemory() = default;
 
-void ZeroInitWorkgroupMemory::Run(CloneContext& ctx, const DataMap&, DataMap&) {
+void ZeroInitWorkgroupMemory::Run(CloneContext& ctx,
+                                  const DataMap&,
+                                  DataMap&) const {
   for (auto* fn : ctx.src->AST().Functions()) {
     if (fn->PipelineStage() == ast::PipelineStage::kCompute) {
       State{ctx}.Run(fn);

src/transform/zero_init_workgroup_memory.h

@@ -39,7 +39,9 @@ class ZeroInitWorkgroupMemory
   /// ProgramBuilder
   /// @param inputs optional extra transform-specific input data
   /// @param outputs optional extra transform-specific output data
-  void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
+  void Run(CloneContext& ctx,
+           const DataMap& inputs,
+           DataMap& outputs) const override;
 
  private:
   struct State;