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Merge pull request #1466 from KhronosGroup/fix-1465
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Clean up and fix awkward conditional branch codegen.
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@HansKristian-Work
HansKristian-Work committed Sep 17, 2020
2 parents 16d9fea + 2144274 commit 8891bd3
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Showing 4 changed files with 215 additions and 37 deletions.
5 changes: 5 additions & 0 deletions reference/opt/shaders/asm/frag/loop-body-dominator-continue-access.asm.frag
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Expand Up @@ -55,6 +55,11 @@ void main()
break;
}
}
if (_225)
{
_228 = _229;
break;
}
_228 = -1;
break;
} while(false);
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67 changes: 67 additions & 0 deletions reference/shaders-no-opt/asm/frag/early-conditional-return-switch.asm.frag
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@@ -0,0 +1,67 @@
#version 450

layout(binding = 0, std140) uniform type_gCBuffarrayIndex
{
uint gArrayIndex;
} gCBuffarrayIndex;

uniform sampler2D SPIRV_Cross_Combinedg_textureArray0SPIRV_Cross_DummySampler;
uniform sampler2D SPIRV_Cross_Combinedg_textureArray1SPIRV_Cross_DummySampler;
uniform sampler2D SPIRV_Cross_Combinedg_textureArray2SPIRV_Cross_DummySampler;
uniform sampler2D SPIRV_Cross_Combinedg_textureArray3SPIRV_Cross_DummySampler;

layout(location = 0) out vec4 out_var_SV_TARGET;

vec4 _32;

void main()
{
vec4 _80;
do
{
vec4 _77;
bool _78;
switch (gCBuffarrayIndex.gArrayIndex)
{
case 0u:
{
_77 = texelFetch(SPIRV_Cross_Combinedg_textureArray0SPIRV_Cross_DummySampler, ivec3(int(gl_FragCoord.x), int(gl_FragCoord.y), 0).xy, 0);
_78 = true;
break;
}
case 1u:
{
_77 = texelFetch(SPIRV_Cross_Combinedg_textureArray1SPIRV_Cross_DummySampler, ivec3(int(gl_FragCoord.x), int(gl_FragCoord.y), 0).xy, 0);
_78 = true;
break;
}
case 2u:
{
_77 = texelFetch(SPIRV_Cross_Combinedg_textureArray2SPIRV_Cross_DummySampler, ivec3(int(gl_FragCoord.x), int(gl_FragCoord.y), 0).xy, 0);
_78 = true;
break;
}
case 3u:
{
_77 = texelFetch(SPIRV_Cross_Combinedg_textureArray3SPIRV_Cross_DummySampler, ivec3(int(gl_FragCoord.x), int(gl_FragCoord.y), 0).xy, 0);
_78 = true;
break;
}
default:
{
_77 = _32;
_78 = false;
break;
}
}
if (_78)
{
_80 = _77;
break;
}
_80 = vec4(0.0, 1.0, 0.0, 1.0);
break;
} while(false);
out_var_SV_TARGET = _80;
}

133 changes: 133 additions & 0 deletions shaders-no-opt/asm/frag/early-conditional-return-switch.asm.frag
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@@ -0,0 +1,133 @@
; SPIR-V
; Version: 1.3
; Generator: Google spiregg; 0
; Bound: 81
; Schema: 0
OpCapability Shader
OpCapability Sampled1D
OpCapability Image1D
OpCapability SampledBuffer
OpCapability ImageBuffer
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %PsTextureLoadArray "main" %gl_FragCoord %out_var_SV_TARGET
OpExecutionMode %PsTextureLoadArray OriginUpperLeft
OpSource HLSL 500
OpName %type_2d_image "type.2d.image"
OpName %type_gCBuffarrayIndex "type.gCBuffarrayIndex"
OpMemberName %type_gCBuffarrayIndex 0 "gArrayIndex"
OpName %gCBuffarrayIndex "gCBuffarrayIndex"
OpName %g_textureArray0 "g_textureArray0"
OpName %g_textureArray1 "g_textureArray1"
OpName %g_textureArray2 "g_textureArray2"
OpName %g_textureArray3 "g_textureArray3"
OpName %out_var_SV_TARGET "out.var.SV_TARGET"
OpName %PsTextureLoadArray "PsTextureLoadArray"
OpDecorate %gl_FragCoord BuiltIn FragCoord
OpDecorate %out_var_SV_TARGET Location 0
OpDecorate %gCBuffarrayIndex DescriptorSet 0
OpDecorate %gCBuffarrayIndex Binding 0
OpDecorate %g_textureArray0 DescriptorSet 0
OpDecorate %g_textureArray0 Binding 0
OpDecorate %g_textureArray1 DescriptorSet 0
OpDecorate %g_textureArray1 Binding 1
OpDecorate %g_textureArray2 DescriptorSet 0
OpDecorate %g_textureArray2 Binding 2
OpDecorate %g_textureArray3 DescriptorSet 0
OpDecorate %g_textureArray3 Binding 3
OpMemberDecorate %type_gCBuffarrayIndex 0 Offset 0
OpDecorate %type_gCBuffarrayIndex Block
%uint = OpTypeInt 32 0
%int = OpTypeInt 32 1
%int_0 = OpConstant %int 0
%float = OpTypeFloat 32
%float_0 = OpConstant %float 0
%float_1 = OpConstant %float 1
%v4float = OpTypeVector %float 4
%18 = OpConstantComposite %v4float %float_0 %float_1 %float_0 %float_1
%type_2d_image = OpTypeImage %float 2D 2 0 0 1 Unknown
%_ptr_UniformConstant_type_2d_image = OpTypePointer UniformConstant %type_2d_image
%type_gCBuffarrayIndex = OpTypeStruct %uint
%_ptr_Uniform_type_gCBuffarrayIndex = OpTypePointer Uniform %type_gCBuffarrayIndex
%_ptr_Input_v4float = OpTypePointer Input %v4float
%_ptr_Output_v4float = OpTypePointer Output %v4float
%void = OpTypeVoid
%24 = OpTypeFunction %void
%_ptr_Uniform_uint = OpTypePointer Uniform %uint
%v3int = OpTypeVector %int 3
%v2int = OpTypeVector %int 2
%gCBuffarrayIndex = OpVariable %_ptr_Uniform_type_gCBuffarrayIndex Uniform
%g_textureArray0 = OpVariable %_ptr_UniformConstant_type_2d_image UniformConstant
%g_textureArray1 = OpVariable %_ptr_UniformConstant_type_2d_image UniformConstant
%g_textureArray2 = OpVariable %_ptr_UniformConstant_type_2d_image UniformConstant
%g_textureArray3 = OpVariable %_ptr_UniformConstant_type_2d_image UniformConstant
%gl_FragCoord = OpVariable %_ptr_Input_v4float Input
%out_var_SV_TARGET = OpVariable %_ptr_Output_v4float Output
%uint_0 = OpConstant %uint 0
%bool = OpTypeBool
%false = OpConstantFalse %bool
%true = OpConstantTrue %bool
%32 = OpUndef %v4float
%PsTextureLoadArray = OpFunction %void None %24
%33 = OpLabel
%34 = OpLoad %v4float %gl_FragCoord
OpSelectionMerge %35 None
OpSwitch %uint_0 %36
%36 = OpLabel
%37 = OpAccessChain %_ptr_Uniform_uint %gCBuffarrayIndex %int_0
%38 = OpLoad %uint %37
OpSelectionMerge %39 None
OpSwitch %38 %40 0 %41 1 %42 2 %43 3 %44
%41 = OpLabel
%45 = OpCompositeExtract %float %34 0
%46 = OpCompositeExtract %float %34 1
%47 = OpConvertFToS %int %45
%48 = OpConvertFToS %int %46
%49 = OpCompositeConstruct %v3int %47 %48 %int_0
%50 = OpVectorShuffle %v2int %49 %49 0 1
%51 = OpLoad %type_2d_image %g_textureArray0
%52 = OpImageFetch %v4float %51 %50 Lod %int_0
OpBranch %39
%42 = OpLabel
%53 = OpCompositeExtract %float %34 0
%54 = OpCompositeExtract %float %34 1
%55 = OpConvertFToS %int %53
%56 = OpConvertFToS %int %54
%57 = OpCompositeConstruct %v3int %55 %56 %int_0
%58 = OpVectorShuffle %v2int %57 %57 0 1
%59 = OpLoad %type_2d_image %g_textureArray1
%60 = OpImageFetch %v4float %59 %58 Lod %int_0
OpBranch %39
%43 = OpLabel
%61 = OpCompositeExtract %float %34 0
%62 = OpCompositeExtract %float %34 1
%63 = OpConvertFToS %int %61
%64 = OpConvertFToS %int %62
%65 = OpCompositeConstruct %v3int %63 %64 %int_0
%66 = OpVectorShuffle %v2int %65 %65 0 1
%67 = OpLoad %type_2d_image %g_textureArray2
%68 = OpImageFetch %v4float %67 %66 Lod %int_0
OpBranch %39
%44 = OpLabel
%69 = OpCompositeExtract %float %34 0
%70 = OpCompositeExtract %float %34 1
%71 = OpConvertFToS %int %69
%72 = OpConvertFToS %int %70
%73 = OpCompositeConstruct %v3int %71 %72 %int_0
%74 = OpVectorShuffle %v2int %73 %73 0 1
%75 = OpLoad %type_2d_image %g_textureArray3
%76 = OpImageFetch %v4float %75 %74 Lod %int_0
OpBranch %39
%40 = OpLabel
OpBranch %39
%39 = OpLabel
%77 = OpPhi %v4float %52 %41 %60 %42 %68 %43 %76 %44 %32 %40
%78 = OpPhi %bool %true %41 %true %42 %true %43 %true %44 %false %40
OpSelectionMerge %79 None
OpBranchConditional %78 %35 %79
%79 = OpLabel
OpBranch %35
%35 = OpLabel
%80 = OpPhi %v4float %77 %39 %18 %79
OpStore %out_var_SV_TARGET %80
OpReturn
OpFunctionEnd
47 changes: 10 additions & 37 deletions spirv_glsl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12732,64 +12732,37 @@ void CompilerGLSL::branch(BlockID from, uint32_t cond, BlockID true_block, Block
auto &from_block = get<SPIRBlock>(from);
BlockID merge_block = from_block.merge == SPIRBlock::MergeSelection ? from_block.next_block : BlockID(0);

// If we branch directly to a selection merge target, we don't need a code path.
// This covers both merge out of if () / else () as well as a break for switch blocks.
bool true_sub = !is_conditional(true_block);
bool false_sub = !is_conditional(false_block);
// If we branch directly to our selection merge target, we don't need a code path.
bool true_block_needs_code = true_block != merge_block || flush_phi_required(from, true_block);
bool false_block_needs_code = false_block != merge_block || flush_phi_required(from, false_block);

bool true_block_is_selection_merge = true_block == merge_block;
bool false_block_is_selection_merge = false_block == merge_block;
if (!true_block_needs_code && !false_block_needs_code)
return;

emit_block_hints(get<SPIRBlock>(from));

if (true_sub)
if (true_block_needs_code)
{
emit_block_hints(get<SPIRBlock>(from));
statement("if (", to_expression(cond), ")");
begin_scope();
branch(from, true_block);
end_scope();

// If we merge to continue, we handle that explicitly in emit_block_chain(),
// so there is no need to branch to it directly here.
// break; is required to handle ladder fallthrough cases, so keep that in for now, even
// if we could potentially handle it in emit_block_chain().
if (false_sub || (!false_block_is_selection_merge && is_continue(false_block)) || is_break(false_block))
if (false_block_needs_code)
{
statement("else");
begin_scope();
branch(from, false_block);
end_scope();
}
else if (flush_phi_required(from, false_block))
{
statement("else");
begin_scope();
flush_phi(from, false_block);
end_scope();
}
}
else if (false_sub)
else if (false_block_needs_code)
{
// Only need false path, use negative conditional.
emit_block_hints(get<SPIRBlock>(from));
statement("if (!", to_enclosed_expression(cond), ")");
begin_scope();
branch(from, false_block);
end_scope();

if ((!true_block_is_selection_merge && is_continue(true_block)) || is_break(true_block))
{
statement("else");
begin_scope();
branch(from, true_block);
end_scope();
}
else if (flush_phi_required(from, true_block))
{
statement("else");
begin_scope();
flush_phi(from, true_block);
end_scope();
}
}
}

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