Incorrect SPIR-V generated when InterlockedAdd present #2828
Description
Bit of an odd one this... I'm compiling this shader library with:
dxc -O3 -T lib_6_4 -spirv -fspv-target-env=vulkan1.1 -enable-16bit-types -Vn ShaderData -Fh Shader.hlsl
The InterlockedAdd in the entryHistogram shader appears to be causing the if statement and corresponding assignment in the entryAverage shader to be ignored. Shader playground link here:
[[vk::binding(0, 0)]]
RWStructuredBuffer<uint> uHistogram;
// Local workgroup histogram
groupshared uint sharedHistogram[256];
[shader("compute")]
[numthreads(16, 16, 1)]
void entryHistogram(uint3 id: SV_DispatchThreadID, uint idx: SV_GroupIndex)
{
// !!! Comment out this line to 'fix' problem !!!
InterlockedAdd(sharedHistogram[0], 1);
}
[shader("compute")]
[numthreads(256, 1, 1)]
void entryAverage(uint3 id: SV_DispatchThreadID, uint idx: SV_GroupIndex)
{
sharedHistogram[idx] = 0;
GroupMemoryBarrierWithGroupSync();
// !!! This if statement and following assignment is ignored !!!
if (idx == 0)
sharedHistogram[idx] = 1;
GroupMemoryBarrierWithGroupSync();
uHistogram[idx] = sharedHistogram[idx];
}
SPIRV generated for entryAverage with the InterlockedAdd:
%entryAverage = OpFunction %void None %23
%30 = OpLabel
%31 = OpLoad %uint %gl_LocalInvocationIndex
%32 = OpAccessChain %_ptr_Workgroup_uint %sharedHistogram %31
OpStore %32 %uint_0
OpControlBarrier %uint_2 %uint_2 %uint_264
OpControlBarrier %uint_2 %uint_2 %uint_264
%33 = OpLoad %uint %32
%34 = OpAccessChain %_ptr_Uniform_uint %uHistogram %int_0 %31
OpStore %34 %33
OpReturn
OpFunctionEnd
SPIRV generated for entryAverage without the InterlockedAdd:
%entryAverage = OpFunction %void None %23
%29 = OpLabel
%30 = OpLoad %uint %gl_LocalInvocationIndex
%31 = OpAccessChain %_ptr_Workgroup_uint %sharedHistogram %30
OpStore %31 %uint_0
OpControlBarrier %uint_2 %uint_2 %uint_264
%32 = OpIEqual %bool %30 %uint_0
OpSelectionMerge %33 None
OpBranchConditional %32 %34 %33
%34 = OpLabel
OpStore %31 %uint_1
OpBranch %33
%33 = OpLabel
OpControlBarrier %uint_2 %uint_2 %uint_264
%35 = OpLoad %uint %31
%36 = OpAccessChain %_ptr_Uniform_uint %uHistogram %int_0 %30
OpStore %36 %35
OpReturn
OpFunctionEnd