SPIRV-Cross/shaders/vulkan/frag/demote-to-helper-forwarding.asm.vk.nocompat.frag
Chip Davis 12a8654784 Don't forward uses of an OpIsHelperInvocationEXT op.
If this is computed *before* a `demote`, but used *after*, forwarding it
will produce the wrong value. This does make for uglier shaders, but
it's necessary right now to ensure correctness.

I needed to use an assembly shader to produce the test for this.
`spirv-opt` is not smart enough (or too smart?) to eliminate the
variable that would be used in GLSL to express this.
2019-07-18 17:32:35 -05:00

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1.6 KiB
JavaScript

; SPIR-V
; Version: 1.3
; Generator: Khronos Glslang Reference Front End; 7
; Bound: 19
; 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" %FragColor
OpExecutionMode %main OriginUpperLeft
OpSource GLSL 450
OpSourceExtension "GL_EXT_demote_to_helper_invocation"
OpName %main "main"
OpName %FragColor "FragColor"
OpDecorate %FragColor Location 0
%void = OpTypeVoid
%3 = OpTypeFunction %void
%bool = OpTypeBool
%_ptr_Function_bool = OpTypePointer Function %bool
%float = OpTypeFloat 32
%v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
%FragColor = OpVariable %_ptr_Output_v4float Output
%float_1 = OpConstant %float 1
%float_0 = OpConstant %float 0
%19 = OpConstantComposite %v4float %float_1 %float_0 %float_0 %float_1
%main = OpFunction %void None %3
%5 = OpLabel
%9 = OpIsHelperInvocationEXT %bool
OpDemoteToHelperInvocationEXT
%10 = OpLogicalNot %bool %9
OpSelectionMerge %12 None
OpBranchConditional %10 %11 %12
%11 = OpLabel
OpStore %FragColor %19
OpBranch %12
%12 = OpLabel
OpReturn
OpFunctionEnd