commit 57b22f36e374ffe2bdffc37f2987d808ce5f9324
author James Price <jrprice@google.com> Wed Aug 27 10:23:13 2025 -0700
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Aug 27 10:23:13 2025 -0700
tree 8ddf584b1a6101257421883c71200a55f9eab420
parent bb7797d063ba9244e6cee6b79fd41598c2d676a1

[spirv-reader] Handle i32 PrimitiveId

We only support u32 for this builtin, so insert a conversion if
needed.

Fixed: 441490952
Change-Id: I637537d4093ec9cc39006709037e15f708ec382a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/259495
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: James Price <jrprice@google.com>

src/tint/lang/spirv/reader/lower/shader_io.cc

diff --git a/src/tint/lang/spirv/reader/lower/shader_io.cc b/src/tint/lang/spirv/reader/lower/shader_io.cc
index 4af4533..3057dc1 100644
--- a/src/tint/lang/spirv/reader/lower/shader_io.cc
+++ b/src/tint/lang/spirv/reader/lower/shader_io.cc
@@ -552,6 +552,7 @@
                     break;
                 }
                 case core::BuiltinValue::kInstanceIndex:
+                case core::BuiltinValue::kPrimitiveIndex:
                 case core::BuiltinValue::kVertexIndex:
                 case core::BuiltinValue::kLocalInvocationIndex:
                 case core::BuiltinValue::kSubgroupInvocationId:
@@ -609,6 +610,7 @@
                     break;
                 }
                 case core::BuiltinValue::kInstanceIndex:
+                case core::BuiltinValue::kPrimitiveIndex:
                 case core::BuiltinValue::kVertexIndex:
                 case core::BuiltinValue::kLocalInvocationIndex:
                 case core::BuiltinValue::kSubgroupInvocationId:

src/tint/lang/spirv/reader/lower/shader_io_test.cc

diff --git a/src/tint/lang/spirv/reader/lower/shader_io_test.cc b/src/tint/lang/spirv/reader/lower/shader_io_test.cc
index 5b461db..5096a85 100644
--- a/src/tint/lang/spirv/reader/lower/shader_io_test.cc
+++ b/src/tint/lang/spirv/reader/lower/shader_io_test.cc
@@ -2306,6 +2306,91 @@
     EXPECT_EQ(expect, str());
 }
 
+TEST_F(SpirvReader_ShaderIOTest, PrimitiveIndex_i32) {
+    auto* idx = b.Var("prim_idx", ty.ptr(core::AddressSpace::kIn, ty.i32()));
+    idx->SetBuiltin(core::BuiltinValue::kPrimitiveIndex);
+    mod.root_block->Append(idx);
+
+    auto* ep = b.Function("foo", ty.i32(), core::ir::Function::PipelineStage::kFragment);
+    ep->SetReturnLocation(0);
+    b.Append(ep->Block(), [&] {
+        auto* idx_value = b.Load(idx);
+        auto* doubled = b.Multiply(ty.i32(), idx_value, 2_i);
+        b.Return(ep, doubled);
+    });
+
+    auto* src = R"(
+$B1: {  # root
+  %prim_idx:ptr<__in, i32, read> = var undef @builtin(primitive_index)
+}
+
+%foo = @fragment func():i32 [@location(0)] {
+  $B2: {
+    %3:i32 = load %prim_idx
+    %4:i32 = mul %3, 2i
+    ret %4
+  }
+}
+)";
+    EXPECT_EQ(src, str());
+
+    auto* expect = R"(
+%foo = @fragment func(%prim_idx:u32 [@primitive_index]):i32 [@location(0)] {
+  $B1: {
+    %3:i32 = convert %prim_idx
+    %4:i32 = mul %3, 2i
+    ret %4
+  }
+}
+)";
+
+    Run(ShaderIO);
+
+    EXPECT_EQ(expect, str());
+}
+
+TEST_F(SpirvReader_ShaderIOTest, PrimitiveIndex_u32) {
+    auto* idx = b.Var("prim_idx", ty.ptr(core::AddressSpace::kIn, ty.u32()));
+    idx->SetBuiltin(core::BuiltinValue::kPrimitiveIndex);
+    mod.root_block->Append(idx);
+
+    auto* ep = b.Function("foo", ty.u32(), core::ir::Function::PipelineStage::kFragment);
+    ep->SetReturnLocation(0);
+    b.Append(ep->Block(), [&] {
+        auto* idx_value = b.Load(idx);
+        auto* doubled = b.Multiply(ty.u32(), idx_value, 2_u);
+        b.Return(ep, doubled);
+    });
+
+    auto* src = R"(
+$B1: {  # root
+  %prim_idx:ptr<__in, u32, read> = var undef @builtin(primitive_index)
+}
+
+%foo = @fragment func():u32 [@location(0)] {
+  $B2: {
+    %3:u32 = load %prim_idx
+    %4:u32 = mul %3, 2u
+    ret %4
+  }
+}
+)";
+    EXPECT_EQ(src, str());
+
+    auto* expect = R"(
+%foo = @fragment func(%prim_idx:u32 [@primitive_index]):u32 [@location(0)] {
+  $B1: {
+    %3:u32 = mul %prim_idx, 2u
+    ret %3
+  }
+}
+)";
+
+    Run(ShaderIO);
+
+    EXPECT_EQ(expect, str());
+}
+
 TEST_F(SpirvReader_ShaderIOTest, LocalInvocationIndex_i32) {
     auto* idx = b.Var("idx", ty.ptr(core::AddressSpace::kIn, ty.i32()));
     idx->SetBuiltin(core::BuiltinValue::kLocalInvocationIndex);