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Consider discard and demote as impure statements.

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Fixes cases where discard and demote are called in pure functions and
the function result is not consumed.
This commit is contained in:
Hans-Kristian Arntzen 2019-09-12 14:21:10 +02:00
parent b32a1b4150
commit bfa76ee2ab
5 changed files with 173 additions and 0 deletions
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22
reference/shaders-no-opt/asm/frag/demote-impure-function-call.vk.nocompat.asm.frag.vk Normal file
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@ -0,0 +1,22 @@
#version 450
#extension GL_EXT_demote_to_helper_invocation : require
layout(location = 0) flat in int vA;
layout(location = 0) out vec4 FragColor;
vec4 foobar(int a)
{
if (a < 0)
{
demote;
}
return vec4(10.0);
}
void main()
{
int param = vA;
vec4 _25 = foobar(param);
FragColor = vec4(10.0);
}

21
reference/shaders-no-opt/asm/frag/discard-impure-function-call.asm.frag Normal file
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@ -0,0 +1,21 @@
#version 450
layout(location = 0) flat in int vA;
layout(location = 0) out vec4 FragColor;
vec4 foobar(int a)
{
if (a < 0)
{
discard;
}
return vec4(10.0);
}
void main()
{
int param = vA;
vec4 _25 = foobar(param);
FragColor = vec4(10.0);
}

63
shaders-no-opt/asm/frag/demote-impure-function-call.vk.nocompat.asm.frag Normal file
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@ -0,0 +1,63 @@
; SPIR-V
; Version: 1.0
; Generator: Khronos Glslang Reference Front End; 7
; Bound: 33
; Schema: 0
OpCapability Shader
OpCapability DemoteToHelperInvocationEXT
OpExtension "SPV_EXT_demote_to_helper_invocation"
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %main "main" %vA %FragColor
OpExecutionMode %main OriginUpperLeft
OpSource GLSL 450
OpSourceExtension "GL_EXT_demote_to_helper_invocation"
OpName %main "main"
OpName %foobar_i1_ "foobar(i1;"
OpName %a "a"
OpName %a_0 "a"
OpName %vA "vA"
OpName %param "param"
OpName %FragColor "FragColor"
OpDecorate %vA Flat
OpDecorate %vA Location 0
OpDecorate %FragColor Location 0
%void = OpTypeVoid
%3 = OpTypeFunction %void
%int = OpTypeInt 32 1
%_ptr_Function_int = OpTypePointer Function %int
%float = OpTypeFloat 32
%v4float = OpTypeVector %float 4
%10 = OpTypeFunction %v4float %_ptr_Function_int
%int_0 = OpConstant %int 0
%bool = OpTypeBool
%float_10 = OpConstant %float 10
%21 = OpConstantComposite %v4float %float_10 %float_10 %float_10 %float_10
%_ptr_Function_v4float = OpTypePointer Function %v4float
%_ptr_Input_int = OpTypePointer Input %int
%vA = OpVariable %_ptr_Input_int Input
%_ptr_Output_v4float = OpTypePointer Output %v4float
%FragColor = OpVariable %_ptr_Output_v4float Output
%main = OpFunction %void None %3
%5 = OpLabel
%a_0 = OpVariable %_ptr_Function_v4float Function
%param = OpVariable %_ptr_Function_int Function
%29 = OpLoad %int %vA
OpStore %param %29
%30 = OpFunctionCall %v4float %foobar_i1_ %param
OpStore %FragColor %21
OpReturn
OpFunctionEnd
%foobar_i1_ = OpFunction %v4float None %10
%a = OpFunctionParameter %_ptr_Function_int
%13 = OpLabel
%14 = OpLoad %int %a
%17 = OpSLessThan %bool %14 %int_0
OpSelectionMerge %19 None
OpBranchConditional %17 %18 %19
%18 = OpLabel
OpDemoteToHelperInvocationEXT
OpBranch %19
%19 = OpLabel
OpReturnValue %21
OpFunctionEnd

59
shaders-no-opt/asm/frag/discard-impure-function-call.asm.frag Normal file
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@ -0,0 +1,59 @@
; SPIR-V
; Version: 1.0
; Generator: Khronos Glslang Reference Front End; 7
; Bound: 34
; Schema: 0
OpCapability Shader
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %main "main" %vA %FragColor
OpExecutionMode %main OriginUpperLeft
OpSource GLSL 450
OpName %main "main"
OpName %foobar_i1_ "foobar(i1;"
OpName %a "a"
OpName %a_0 "a"
OpName %vA "vA"
OpName %param "param"
OpName %FragColor "FragColor"
OpDecorate %vA Flat
OpDecorate %vA Location 0
OpDecorate %FragColor Location 0
%void = OpTypeVoid
%3 = OpTypeFunction %void
%int = OpTypeInt 32 1
%_ptr_Function_int = OpTypePointer Function %int
%float = OpTypeFloat 32
%v4float = OpTypeVector %float 4
%10 = OpTypeFunction %v4float %_ptr_Function_int
%int_0 = OpConstant %int 0
%bool = OpTypeBool
%float_10 = OpConstant %float 10
%22 = OpConstantComposite %v4float %float_10 %float_10 %float_10 %float_10
%_ptr_Function_v4float = OpTypePointer Function %v4float
%_ptr_Input_int = OpTypePointer Input %int
%vA = OpVariable %_ptr_Input_int Input
%_ptr_Output_v4float = OpTypePointer Output %v4float
%FragColor = OpVariable %_ptr_Output_v4float Output
%main = OpFunction %void None %3
%5 = OpLabel
%a_0 = OpVariable %_ptr_Function_v4float Function
%param = OpVariable %_ptr_Function_int Function
%30 = OpLoad %int %vA
OpStore %param %30
%31 = OpFunctionCall %v4float %foobar_i1_ %param
OpStore %FragColor %22
OpReturn
OpFunctionEnd
%foobar_i1_ = OpFunction %v4float None %10
%a = OpFunctionParameter %_ptr_Function_int
%13 = OpLabel
%14 = OpLoad %int %a
%17 = OpSLessThan %bool %14 %int_0
OpSelectionMerge %19 None
OpBranchConditional %17 %18 %19
%18 = OpLabel
OpKill
%19 = OpLabel
OpReturnValue %22
OpFunctionEnd

8
spirv_cross.cpp
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@ -88,6 +88,10 @@ bool Compiler::variable_storage_is_aliased(const SPIRVariable &v)
bool Compiler::block_is_pure(const SPIRBlock &block)
{
// This is a global side effect of the function.
if (block.terminator == SPIRBlock::Kill)
return false;
for (auto &i : block.ops)
{
auto ops = stream(i);
@ -156,6 +160,10 @@ bool Compiler::block_is_pure(const SPIRBlock &block)
// OpExtInst is potentially impure depending on extension, but GLSL builtins are at least pure.
case OpDemoteToHelperInvocationEXT:
// This is a global side effect of the function.
return false;
default:
break;
}