Add pass to eliminate dead output components (#4982)

This pass eliminates components of output variables that are not stored
to. Currently this just eliminates trailing components of arrays and
structs, all of which are dead.

WARNING: This pass is not designed to be a standalone pass as it can
cause interface incompatibiliies with the following shader in the
pipeline. See the comment in optimizer.hpp for best usage. This pass is
currently available only through the API; it is not available in the CLI.

This commit also fixes a bug in CreateDecoration() which is part of the
system of generating SPIR-V from the Type manager.

1 files changed, 149 insertions, 0 deletions

diff --git a/test/opt/eliminate_dead_input_components_test.cpp b/test/opt/eliminate_dead_input_components_test.cpp
index 822914a86..2c2e63612 100644
--- a/test/opt/eliminate_dead_input_components_test.cpp
+++ b/test/opt/eliminate_dead_input_components_test.cpp
@@ -463,6 +463,155 @@ TEST_F(ElimDeadInputComponentsTest, ElimStructMember) {
   SinglePassRunAndMatch<EliminateDeadInputComponentsPass>(text, true);
 }
 
+TEST_F(ElimDeadInputComponentsTest, ElimOutputStructMember) {
+  // Should eliminate uv from Vertex and all but gl_Position from gl_PerVertex
+  //
+  // #version 450
+  //
+  // out Vertex {
+  //   vec4 Cd;
+  //   vec2 uv;
+  // } oVert;
+  //
+  // in vec3 P;
+  //
+  // void main()
+  // {
+  //   vec4 worldSpacePos = vec4(P, 1);
+  //   oVert.Cd = vec4(1, 0.5, 0, 1);
+  //   gl_Position = worldSpacePos;
+  // }
+
+  const std::string text = R"(
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Vertex %main "main" %P %oVert %_
+               OpSource GLSL 450
+               OpName %main "main"
+               OpName %P "P"
+               OpName %Vertex "Vertex"
+               OpMemberName %Vertex 0 "Cd"
+               OpMemberName %Vertex 1 "uv"
+               OpName %oVert "oVert"
+               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 %_ ""
+               OpDecorate %P Location 0
+               OpDecorate %Vertex Block
+               OpDecorate %oVert Location 0
+               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
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+    %v3float = OpTypeVector %float 3
+%_ptr_Input_v3float = OpTypePointer Input %v3float
+          %P = OpVariable %_ptr_Input_v3float Input
+    %float_1 = OpConstant %float 1
+    %v2float = OpTypeVector %float 2
+     %Vertex = OpTypeStruct %v4float %v2float
+%_ptr_Output_Vertex = OpTypePointer Output %Vertex
+      %oVert = OpVariable %_ptr_Output_Vertex Output
+        %int = OpTypeInt 32 1
+      %int_0 = OpConstant %int 0
+  %float_0_5 = OpConstant %float 0.5
+    %float_0 = OpConstant %float 0
+         %27 = OpConstantComposite %v4float %float_1 %float_0_5 %float_0 %float_1
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+       %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
+; CHECK: %Vertex = OpTypeStruct %v4float %v2float
+; CHECK: %gl_PerVertex = OpTypeStruct %v4float %float %_arr_float_uint_1 %_arr_float_uint_1
+; CHECK: %_ptr_Output_gl_PerVertex = OpTypePointer Output %gl_PerVertex
+; CHECK: [[sty:%\w+]] = OpTypeStruct %v4float
+; CHECK: [[pty:%\w+]] = OpTypePointer Output [[sty]]
+; CHECK: %oVert = OpVariable [[pty]] Output
+; CHECK: [[sty2:%\w+]] = OpTypeStruct %v4float
+; CHECK: [[pty2:%\w+]] = OpTypePointer Output [[sty2]]
+; CHECK: %_ = OpVariable [[pty2]] Output
+       %main = OpFunction %void None %3
+          %5 = OpLabel
+         %13 = OpLoad %v3float %P
+         %15 = OpCompositeExtract %float %13 0
+         %16 = OpCompositeExtract %float %13 1
+         %17 = OpCompositeExtract %float %13 2
+         %18 = OpCompositeConstruct %v4float %15 %16 %17 %float_1
+         %29 = OpAccessChain %_ptr_Output_v4float %oVert %int_0
+               OpStore %29 %27
+         %37 = OpAccessChain %_ptr_Output_v4float %_ %int_0
+               OpStore %37 %18
+               OpReturn
+               OpFunctionEnd
+)";
+
+  SetTargetEnv(SPV_ENV_VULKAN_1_3);
+  SetAssembleOptions(SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  SinglePassRunAndMatch<EliminateDeadInputComponentsPass>(text, true, true);
+}
+
+TEST_F(ElimDeadInputComponentsTest, ElimOutputArrayMembers) {
+  // Should reduce to uv[2]
+  //
+  // #version 450
+  //
+  // layout(location = 0) out vec2 uv[8];
+  //
+  // void main()
+  // {
+  //     uv[1] = vec2(1, 0.5);
+  // }
+
+  const std::string text = R"(
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Vertex %main "main" %uv
+               OpSource GLSL 450
+               OpName %main "main"
+               OpName %uv "uv"
+               OpDecorate %uv Location 0
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+      %float = OpTypeFloat 32
+    %v2float = OpTypeVector %float 2
+       %uint = OpTypeInt 32 0
+     %uint_8 = OpConstant %uint 8
+%_arr_v2float_uint_8 = OpTypeArray %v2float %uint_8
+%_ptr_Output__arr_v2float_uint_8 = OpTypePointer Output %_arr_v2float_uint_8
+         %uv = OpVariable %_ptr_Output__arr_v2float_uint_8 Output
+;CHECK-NOT:         %uv = OpVariable %_ptr_Output__arr_v2float_uint_8 Output
+;CHECK:             %uv = OpVariable %_ptr_Output__arr_v2float_uint_2 Output
+        %int = OpTypeInt 32 1
+      %int_1 = OpConstant %int 1
+    %float_1 = OpConstant %float 1
+  %float_0_5 = OpConstant %float 0.5
+         %17 = OpConstantComposite %v2float %float_1 %float_0_5
+%_ptr_Output_v2float = OpTypePointer Output %v2float
+       %main = OpFunction %void None %3
+          %5 = OpLabel
+         %19 = OpAccessChain %_ptr_Output_v2float %uv %int_1
+               OpStore %19 %17
+               OpReturn
+               OpFunctionEnd
+)";
+
+  SetTargetEnv(SPV_ENV_VULKAN_1_3);
+  SetAssembleOptions(SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  SinglePassRunAndMatch<EliminateDeadInputComponentsPass>(text, true, true);
+}
+
 }  // namespace
 }  // namespace opt
 }  // namespace spvtools