Convert @group to an expression

This CL updates the group attribute to store an expression
instead of a single value. The parser always produces an
IntLiteralExpression at the moment.

Bug: tint:1633
Change-Id: Ice05c26d652c7f5c21825f745f270e96e3d88e08
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/100441
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/tint/ast/builtin_texture_helper_test.cc

@@ -142,7 +142,7 @@ const ast::Type* TextureOverloadCase::BuildResultVectorComponentType(ProgramBuil
 
 const ast::Variable* TextureOverloadCase::BuildTextureVariable(ProgramBuilder* b) const {
     utils::Vector attrs{
-        b->create<ast::GroupAttribute>(0u),
+        b->Group(0_u),
         b->Binding(0_a),
     };
     switch (texture_kind) {
@@ -175,7 +175,7 @@ const ast::Variable* TextureOverloadCase::BuildTextureVariable(ProgramBuilder* b
 }
 
 const ast::Variable* TextureOverloadCase::BuildSamplerVariable(ProgramBuilder* b) const {
-    utils::Vector attrs = {b->Group(0u), b->Binding(1_a)};
+    utils::Vector attrs = {b->Group(0_a), b->Binding(1_a)};
     return b->GlobalVar("sampler", b->ty.sampler(sampler_kind), attrs);
 }
 

src/tint/ast/group_attribute.cc

@@ -22,7 +22,10 @@ TINT_INSTANTIATE_TYPEINFO(tint::ast::GroupAttribute);
 
 namespace tint::ast {
 
-GroupAttribute::GroupAttribute(ProgramID pid, NodeID nid, const Source& src, uint32_t val)
+GroupAttribute::GroupAttribute(ProgramID pid,
+                               NodeID nid,
+                               const Source& src,
+                               const ast::Expression* val)
     : Base(pid, nid, src), value(val) {}
 
 GroupAttribute::~GroupAttribute() = default;
@@ -34,7 +37,8 @@ std::string GroupAttribute::Name() const {
 const GroupAttribute* GroupAttribute::Clone(CloneContext* ctx) const {
     // Clone arguments outside of create() call to have deterministic ordering
     auto src = ctx->Clone(source);
-    return ctx->dst->create<GroupAttribute>(src, value);
+    auto* value_ = ctx->Clone(value);
+    return ctx->dst->create<GroupAttribute>(src, value_);
 }
 
 }  // namespace tint::ast

src/tint/ast/group_attribute.h

@@ -18,6 +18,7 @@
 #include <string>
 
 #include "src/tint/ast/attribute.h"
+#include "src/tint/ast/expression.h"
 
 namespace tint::ast {
 
@@ -28,8 +29,8 @@ class GroupAttribute final : public Castable<GroupAttribute, Attribute> {
     /// @param pid the identifier of the program that owns this node
     /// @param nid the unique node identifier
     /// @param src the source of this node
-    /// @param value the group value
-    GroupAttribute(ProgramID pid, NodeID nid, const Source& src, uint32_t value);
+    /// @param value the group value expression
+    GroupAttribute(ProgramID pid, NodeID nid, const Source& src, const ast::Expression* value);
     ~GroupAttribute() override;
 
     /// @returns the WGSL name for the attribute
@@ -41,8 +42,8 @@ class GroupAttribute final : public Castable<GroupAttribute, Attribute> {
     /// @return the newly cloned node
     const GroupAttribute* Clone(CloneContext* ctx) const override;
 
-    /// The group value
-    const uint32_t value;
+    /// The group value expression
+    const ast::Expression* const value;
 };
 
 }  // namespace tint::ast

src/tint/ast/group_attribute_test.cc

@@ -17,11 +17,12 @@
 namespace tint::ast {
 namespace {
 
+using namespace tint::number_suffixes;  // NOLINT
 using GroupAttributeTest = TestHelper;
 
 TEST_F(GroupAttributeTest, Creation) {
-    auto* d = create<GroupAttribute>(2u);
-    EXPECT_EQ(2u, d->value);
+    auto* d = Group(2_a);
+    EXPECT_TRUE(d->value->Is<IntLiteralExpression>());
 }
 
 }  // namespace

src/tint/ast/variable_test.cc

@@ -106,7 +106,7 @@ TEST_F(VariableTest, WithAttributes) {
 }
 
 TEST_F(VariableTest, HasBindingPoint_BothProvided) {
-    auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, Binding(2_a), Group(1));
+    auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, Binding(2_a), Group(1_a));
     EXPECT_TRUE(var->HasBindingPoint());
 }
 
@@ -121,7 +121,7 @@ TEST_F(VariableTest, HasBindingPoint_MissingGroupAttribute) {
 }
 
 TEST_F(VariableTest, HasBindingPoint_MissingBindingAttribute) {
-    auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, Group(1));
+    auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, Group(1_a));
     EXPECT_FALSE(var->HasBindingPoint());
 }