resolver: Allocate IDs for named pipeline constants

Keep track of any constant IDs specified in the shader, and then
allocate IDs for the remaining constants when creating the semantic
info.

Bug: tint:755
Change-Id: I6a76b1193cac459b62582cde7469b092dde51d5d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50841
Commit-Queue: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/CMakeLists.txt

@@ -550,6 +550,7 @@ if(${TINT_BUILD_TESTS})
     resolver/intrinsic_test.cc
     resolver/is_host_shareable_test.cc
     resolver/is_storeable_test.cc
+    resolver/pipeline_overridable_constant_test.cc
     resolver/resolver_test_helper.cc
     resolver/resolver_test_helper.h
     resolver/resolver_test.cc

src/program_builder.h

@@ -38,6 +38,7 @@
 #include "src/ast/member_accessor_expression.h"
 #include "src/ast/module.h"
 #include "src/ast/multisampled_texture.h"
+#include "src/ast/override_decoration.h"
 #include "src/ast/pointer.h"
 #include "src/ast/return_statement.h"
 #include "src/ast/sampled_texture.h"
@@ -1786,6 +1787,32 @@ class ProgramBuilder {
     return create<ast::LocationDecoration>(source_, location);
   }
 
+  /// Creates an ast::OverrideDecoration with a specific constant ID
+  /// @param source the source information
+  /// @param id the id value
+  /// @returns the override decoration pointer
+  ast::OverrideDecoration* Override(const Source& source, uint32_t id) {
+    return create<ast::OverrideDecoration>(source, id);
+  }
+
+  /// Creates an ast::OverrideDecoration with a specific constant ID
+  /// @param id the optional id value
+  /// @returns the override decoration pointer
+  ast::OverrideDecoration* Override(uint32_t id) {
+    return Override(source_, id);
+  }
+
+  /// Creates an ast::OverrideDecoration without a constant ID
+  /// @param source the source information
+  /// @returns the override decoration pointer
+  ast::OverrideDecoration* Override(const Source& source) {
+    return create<ast::OverrideDecoration>(source);
+  }
+
+  /// Creates an ast::OverrideDecoration without a constant ID
+  /// @returns the override decoration pointer
+  ast::OverrideDecoration* Override() { return Override(source_); }
+
   /// Creates an ast::StageDecoration
   /// @param source the source information
   /// @param stage the pipeline stage

src/resolver/pipeline_overridable_constant_test.cc

@@ -0,0 +1,113 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/resolver/resolver.h"
+
+#include "gmock/gmock.h"
+#include "src/resolver/resolver_test_helper.h"
+
+using ::testing::UnorderedElementsAre;
+
+namespace tint {
+namespace resolver {
+namespace {
+
+using ResolverPipelineOverridableConstantTest = ResolverTest;
+
+TEST_F(ResolverPipelineOverridableConstantTest, NonOverridable) {
+  auto* a = GlobalConst("a", ty.f32(), Construct(ty.f32()));
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  auto* sem_a = Sem().Get(a);
+  ASSERT_NE(sem_a, nullptr);
+  EXPECT_EQ(sem_a->Declaration(), a);
+  EXPECT_FALSE(sem_a->IsPipelineConstant());
+}
+
+TEST_F(ResolverPipelineOverridableConstantTest, WithId) {
+  auto* a = GlobalConst("a", ty.f32(), Construct(ty.f32()), {Override(7u)});
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  auto* sem_a = Sem().Get(a);
+  ASSERT_NE(sem_a, nullptr);
+  EXPECT_EQ(sem_a->Declaration(), a);
+  EXPECT_TRUE(sem_a->IsPipelineConstant());
+  EXPECT_EQ(sem_a->ConstantId(), 7u);
+}
+
+TEST_F(ResolverPipelineOverridableConstantTest, WithoutId) {
+  auto* a = GlobalConst("a", ty.f32(), Construct(ty.f32()), {Override()});
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  auto* sem_a = Sem().Get(a);
+  ASSERT_NE(sem_a, nullptr);
+  EXPECT_EQ(sem_a->Declaration(), a);
+  EXPECT_TRUE(sem_a->IsPipelineConstant());
+  EXPECT_EQ(sem_a->ConstantId(), 0u);
+}
+
+TEST_F(ResolverPipelineOverridableConstantTest, WithAndWithoutIds) {
+  std::vector<ast::Variable*> variables;
+  variables.push_back(
+      GlobalConst("a", ty.f32(), Construct(ty.f32()), {Override()}));
+  variables.push_back(
+      GlobalConst("b", ty.f32(), Construct(ty.f32()), {Override()}));
+  variables.push_back(
+      GlobalConst("c", ty.f32(), Construct(ty.f32()), {Override(2u)}));
+  variables.push_back(
+      GlobalConst("d", ty.f32(), Construct(ty.f32()), {Override(4u)}));
+  variables.push_back(
+      GlobalConst("e", ty.f32(), Construct(ty.f32()), {Override()}));
+  variables.push_back(
+      GlobalConst("f", ty.f32(), Construct(ty.f32()), {Override(1u)}));
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  std::vector<uint16_t> constant_ids;
+  for (auto* var : variables) {
+    auto* sem = Sem().Get(var);
+    ASSERT_NE(sem, nullptr);
+    constant_ids.push_back(sem->ConstantId());
+  }
+  EXPECT_THAT(constant_ids, UnorderedElementsAre(0u, 3u, 2u, 4u, 5u, 1u));
+}
+
+TEST_F(ResolverPipelineOverridableConstantTest, DuplicateIds) {
+  GlobalConst("a", ty.f32(), Construct(ty.f32()),
+              {Override(Source{{12, 34}}, 7u)});
+  GlobalConst("b", ty.f32(), Construct(ty.f32()),
+              {Override(Source{{56, 78}}, 7u)});
+
+  EXPECT_FALSE(r()->Resolve());
+
+  EXPECT_EQ(r()->error(), R"(56:78 error: pipeline constant IDs must be unique
+12:34 note: a pipeline constant with an ID of 7 was previously declared here:)");
+}
+
+TEST_F(ResolverPipelineOverridableConstantTest, IdTooLarge) {
+  GlobalConst("a", ty.f32(), Construct(ty.f32()),
+              {Override(Source{{12, 34}}, 65536u)});
+
+  EXPECT_FALSE(r()->Resolve());
+
+  EXPECT_EQ(r()->error(),
+            "12:34 error: pipeline constant IDs must be between 0 and 65535");
+}
+
+}  // namespace
+}  // namespace resolver
+}  // namespace tint

src/resolver/resolver.cc

@@ -519,6 +519,13 @@ bool Resolver::GlobalVariable(ast::Variable* var) {
 
   for (auto* deco : var->decorations()) {
     Mark(deco);
+
+    if (auto* override_deco = deco->As<ast::OverrideDecoration>()) {
+      // Track the constant IDs that are specified in the shader.
+      if (override_deco->HasValue()) {
+        constant_ids_.emplace(override_deco->value(), info);
+      }
+    }
   }
 
   if (auto bp = var->binding_point()) {
@@ -543,7 +550,30 @@ bool Resolver::GlobalVariable(ast::Variable* var) {
 bool Resolver::ValidateGlobalVariable(const VariableInfo* info) {
   for (auto* deco : info->declaration->decorations()) {
     if (info->declaration->is_const()) {
-      if (!deco->Is<ast::OverrideDecoration>()) {
+      if (auto* override_deco = deco->As<ast::OverrideDecoration>()) {
+        if (override_deco->HasValue()) {
+          uint32_t id = override_deco->value();
+          auto itr = constant_ids_.find(id);
+          if (itr != constant_ids_.end() && itr->second != info) {
+            diagnostics_.add_error("pipeline constant IDs must be unique",
+                                   deco->source());
+            diagnostics_.add_note("a pipeline constant with an ID of " +
+                                      std::to_string(id) +
+                                      " was previously declared "
+                                      "here:",
+                                  ast::GetDecoration<ast::OverrideDecoration>(
+                                      itr->second->declaration->decorations())
+                                      ->source());
+            return false;
+          }
+          if (id > 65535) {
+            diagnostics_.add_error(
+                "pipeline constant IDs must be between 0 and 65535",
+                deco->source());
+            return false;
+          }
+        }
+      } else {
         diagnostics_.add_error("decoration is not valid for constants",
                                deco->source());
         return false;
@@ -2244,12 +2274,42 @@ void Resolver::CreateSemanticNodes() const {
     }
   }
 
+  // The next pipeline constant ID to try to allocate.
+  uint16_t next_constant_id = 0;
+
   // Create semantic nodes for all ast::Variables
   for (auto it : variable_to_info_) {
     auto* var = it.first;
     auto* info = it.second;
-    auto* sem_var =
-        builder_->create<sem::Variable>(var, info->type, info->storage_class);
+
+    sem::Variable* sem_var = nullptr;
+
+    if (auto* override_deco =
+            ast::GetDecoration<ast::OverrideDecoration>(var->decorations())) {
+      // Create a pipeline overridable constant.
+      uint16_t constant_id;
+      if (override_deco->HasValue()) {
+        constant_id = override_deco->value();
+      } else {
+        // No ID was specified, so allocate the next available ID.
+        constant_id = next_constant_id;
+        while (constant_ids_.count(constant_id)) {
+          if (constant_id == UINT16_MAX) {
+            TINT_ICE(builder_->Diagnostics())
+                << "no more pipeline constant IDs available";
+            return;
+          }
+          constant_id++;
+        }
+        next_constant_id = constant_id + 1;
+      }
+
+      sem_var = builder_->create<sem::Variable>(var, info->type, constant_id);
+    } else {
+      sem_var =
+          builder_->create<sem::Variable>(var, info->type, info->storage_class);
+    }
+
     std::vector<const sem::VariableUser*> users;
     for (auto* user : info->users) {
       // Create semantic node for the identifier expression if necessary

src/resolver/resolver.h

@@ -347,6 +347,7 @@ class Resolver {
   std::unordered_map<const ast::Expression*, ExpressionInfo> expr_info_;
   std::unordered_map<Symbol, sem::Type*> named_types_;
   std::unordered_set<const ast::Node*> marked_;
+  std::unordered_map<uint32_t, const VariableInfo*> constant_ids_;
   FunctionInfo* current_function_ = nullptr;
   sem::Statement* current_statement_ = nullptr;
   BlockAllocator<VariableInfo> variable_infos_;

src/sem/variable.cc

@@ -26,7 +26,19 @@ namespace sem {
 Variable::Variable(const ast::Variable* declaration,
                    const sem::Type* type,
                    ast::StorageClass storage_class)
-    : declaration_(declaration), type_(type), storage_class_(storage_class) {}
+    : declaration_(declaration),
+      type_(type),
+      storage_class_(storage_class),
+      is_pipeline_constant_(false) {}
+
+Variable::Variable(const ast::Variable* declaration,
+                   const sem::Type* type,
+                   uint16_t constant_id)
+    : declaration_(declaration),
+      type_(type),
+      storage_class_(ast::StorageClass::kNone),
+      is_pipeline_constant_(true),
+      constant_id_(constant_id) {}
 
 Variable::~Variable() = default;
 

src/sem/variable.h

@@ -37,7 +37,7 @@ class VariableUser;
 /// Variable holds the semantic information for variables.
 class Variable : public Castable<Variable, Node> {
  public:
-  /// Constructor
+  /// Constructor for variables and non-overridable constants
   /// @param declaration the AST declaration node
   /// @param type the variable type
   /// @param storage_class the variable storage class
@@ -45,6 +45,14 @@ class Variable : public Castable<Variable, Node> {
            const sem::Type* type,
            ast::StorageClass storage_class);
 
+  /// Constructor for overridable pipeline constants
+  /// @param declaration the AST declaration node
+  /// @param type the variable type
+  /// @param constant_id the pipeline constant ID
+  Variable(const ast::Variable* declaration,
+           const sem::Type* type,
+           uint16_t constant_id);
+
   /// Destructor
   ~Variable() override;
 
@@ -63,11 +71,19 @@ class Variable : public Castable<Variable, Node> {
   /// @param user the user to add
   void AddUser(const VariableUser* user) { users_.emplace_back(user); }
 
+  /// @returns true if this variable is an overridable pipeline constant
+  bool IsPipelineConstant() const { return is_pipeline_constant_; }
+
+  /// @returns the pipeline constant ID associated with the variable
+  uint32_t ConstantId() const { return constant_id_; }
+
  private:
   const ast::Variable* const declaration_;
   const sem::Type* const type_;
   ast::StorageClass const storage_class_;
   std::vector<const VariableUser*> users_;
+  const bool is_pipeline_constant_;
+  const uint16_t constant_id_ = 0;
 };
 
 /// VariableUser holds the semantic information for an identifier expression

test/BUILD.gn

@@ -257,6 +257,7 @@ tint_unittests_source_set("tint_unittests_core_src") {
     "../src/resolver/intrinsic_test.cc",
     "../src/resolver/is_host_shareable_test.cc",
     "../src/resolver/is_storeable_test.cc",
+    "../src/resolver/pipeline_overridable_constant_test.cc",
     "../src/resolver/resolver_test.cc",
     "../src/resolver/resolver_test_helper.cc",
     "../src/resolver/resolver_test_helper.h",