Add test case for builtin only accessed in function parsed after the entry point function

naga/tests/in/spv/builtin-accessed-outside-entrypoint.spvasm

@@ -0,0 +1,90 @@
+;; Ensure builtin binding isn't removed by unused gl_PerVertex builtin culling when
+;; the builtin is used in a function defined after (in the SPIRV) the entry point.
+;;
+;; Generated from the following glsl via `glslc` (without `-O` flag):
+;;
+;; ```glsl
+;; #version 450
+;;
+;; void builtin_usage() {
+;;     gl_Position = vec4(
+;;         (gl_VertexIndex == 0) ? -4.0 : 1.0,
+;;         (gl_VertexIndex == 2) ? 4.0 : -1.0,
+;;         0.0,
+;;         1.0
+;;     );
+;; }
+;;
+;; void main()
+;; {
+;;     builtin_usage();
+;; }
+;; ```
+;;
+; SPIR-V
+; Version: 1.0
+; Generator: Google Shaderc over Glslang; 11
+; Bound: 37
+; Schema: 0
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Vertex %main "main" %_ %gl_VertexIndex
+               OpSource GLSL 450
+               OpSourceExtension "GL_GOOGLE_cpp_style_line_directive"
+               OpSourceExtension "GL_GOOGLE_include_directive"
+               OpName %main "main"
+               OpName %builtin_usage_ "builtin_usage("
+               OpName %gl_PerVertex "gl_PerVertex"
+               OpMemberName %gl_PerVertex 0 "gl_Position"
+               OpMemberName %gl_PerVertex 1 "gl_PointSize"
+               OpMemberName %gl_PerVertex 2 "gl_ClipDistance"
+               OpMemberName %gl_PerVertex 3 "gl_CullDistance"
+               OpName %_ ""
+               OpName %gl_VertexIndex "gl_VertexIndex"
+               OpMemberDecorate %gl_PerVertex 0 BuiltIn Position
+               OpMemberDecorate %gl_PerVertex 1 BuiltIn PointSize
+               OpMemberDecorate %gl_PerVertex 2 BuiltIn ClipDistance
+               OpMemberDecorate %gl_PerVertex 3 BuiltIn CullDistance
+               OpDecorate %gl_PerVertex Block
+               OpDecorate %gl_VertexIndex BuiltIn VertexIndex
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+       %uint = OpTypeInt 32 0
+     %uint_1 = OpConstant %uint 1
+%_arr_float_uint_1 = OpTypeArray %float %uint_1
+%gl_PerVertex = OpTypeStruct %v4float %float %_arr_float_uint_1 %_arr_float_uint_1
+%_ptr_Output_gl_PerVertex = OpTypePointer Output %gl_PerVertex
+          %_ = OpVariable %_ptr_Output_gl_PerVertex Output
+        %int = OpTypeInt 32 1
+      %int_0 = OpConstant %int 0
+%_ptr_Input_int = OpTypePointer Input %int
+%gl_VertexIndex = OpVariable %_ptr_Input_int Input
+       %bool = OpTypeBool
+   %float_n4 = OpConstant %float -4
+    %float_1 = OpConstant %float 1
+      %int_2 = OpConstant %int 2
+    %float_4 = OpConstant %float 4
+   %float_n1 = OpConstant %float -1
+    %float_0 = OpConstant %float 0
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+       %main = OpFunction %void None %3
+          %5 = OpLabel
+         %36 = OpFunctionCall %void %builtin_usage_
+               OpReturn
+               OpFunctionEnd
+%builtin_usage_ = OpFunction %void None %3
+          %7 = OpLabel
+         %20 = OpLoad %int %gl_VertexIndex
+         %22 = OpIEqual %bool %20 %int_0
+         %25 = OpSelect %float %22 %float_n4 %float_1
+         %26 = OpLoad %int %gl_VertexIndex
+         %28 = OpIEqual %bool %26 %int_2
+         %31 = OpSelect %float %28 %float_4 %float_n1
+         %33 = OpCompositeConstruct %v4float %25 %31 %float_0 %float_1
+         %35 = OpAccessChain %_ptr_Output_v4float %_ %int_0
+               OpStore %35 %33
+               OpReturn
+               OpFunctionEnd

naga/tests/out/wgsl/builtin-accessed-outside-entrypoint.wgsl

@@ -0,0 +1,31 @@
+struct gl_PerVertex {
+    @builtin(position) gl_Position: vec4<f32>,
+    gl_PointSize: f32,
+    gl_ClipDistance: array<f32, 1>,
+    gl_CullDistance: array<f32, 1>,
+}
+
+var<private> unnamed: gl_PerVertex = gl_PerVertex(vec4<f32>(0f, 0f, 0f, 1f), 1f, array<f32, 1>(), array<f32, 1>());
+var<private> gl_VertexIndex_1: i32;
+
+fn builtin_usage() {
+    let _e9 = gl_VertexIndex_1;
+    let _e12 = gl_VertexIndex_1;
+    unnamed.gl_Position = vec4<f32>(select(1f, -4f, (_e9 == 0i)), select(-1f, 4f, (_e12 == 2i)), 0f, 1f);
+    return;
+}
+
+fn main_1() {
+    builtin_usage();
+    return;
+}
+
+@vertex 
+fn main(@builtin(vertex_index) gl_VertexIndex: u32) -> @builtin(position) vec4<f32> {
+    gl_VertexIndex_1 = i32(gl_VertexIndex);
+    main_1();
+    let _e6 = unnamed.gl_Position.y;
+    unnamed.gl_Position.y = -(_e6);
+    let _e8 = unnamed.gl_Position;
+    return _e8;
+}

naga/tests/snapshots.rs

@@ -891,6 +891,7 @@ fn convert_spv_all() {
         true,
         Targets::METAL | Targets::GLSL | Targets::HLSL | Targets::WGSL,
     );
+    convert_spv("builtin-accessed-outside-entrypoint", true, Targets::WGSL);
 }
 
 #[cfg(feature = "glsl-in")]