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Change Volatile generation for HelperInvocation

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For SPIR-V 1.6 HelperInvocation accesses need to be volatile to avoid
undefined values when shaders execute 'demote'. Previously this was
always decorated on the gl_HelperInvocation variable, but this is not
valid when the Vulkan memory model is in use.

When the memory model is enabled, stop decorating the variable
declaration and apply the memory semantic to access chain loads instead.

Fixes #3042
This commit is contained in:
Graeme Leese 2022-10-04 16:16:52 +01:00
parent 5755de46b0
commit d570b2b05b
1 changed files with 12 additions and 1 deletions
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13
SPIRV/GlslangToSpv.cpp
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@ -4741,6 +4741,16 @@ spv::Id TGlslangToSpvTraverser::accessChainLoad(const glslang::TType& type)
spv::Builder::AccessChain::CoherentFlags coherentFlags = builder.getAccessChain().coherentFlags;
coherentFlags |= TranslateCoherent(type);
spv::MemoryAccessMask accessMask = spv::MemoryAccessMask(TranslateMemoryAccess(coherentFlags) & ~spv::MemoryAccessMakePointerAvailableKHRMask);
// If the value being loaded is HelperInvocation, SPIR-V 1.6 is being generated (so that
// SPV_EXT_demote_to_helper_invocation is in core) and the memory model is in use, add
// the Volatile MemoryAccess semantic.
if (type.getQualifier().builtIn == glslang::EbvHelperInvocation &&
glslangIntermediate->usingVulkanMemoryModel() &&
glslangIntermediate->getSpv().spv >= glslang::EShTargetSpv_1_6) {
accessMask = spv::MemoryAccessMask(accessMask | spv::MemoryAccessVolatileMask);
}
unsigned int alignment = builder.getAccessChain().alignment;
alignment |= type.getBufferReferenceAlignment();
@ -4748,7 +4758,7 @@ spv::Id TGlslangToSpvTraverser::accessChainLoad(const glslang::TType& type)
TranslateNonUniformDecoration(builder.getAccessChain().coherentFlags),
TranslateNonUniformDecoration(type.getQualifier()),
nominalTypeId,
spv::MemoryAccessMask(TranslateMemoryAccess(coherentFlags) & ~spv::MemoryAccessMakePointerAvailableKHRMask),
accessMask,
TranslateMemoryScope(coherentFlags),
alignment);
@ -8968,6 +8978,7 @@ spv::Id TGlslangToSpvTraverser::getSymbolId(const glslang::TIntermSymbol* symbol
// Add volatile decoration to HelperInvocation for spirv1.6 and beyond
if (builtIn == spv::BuiltInHelperInvocation &&
!glslangIntermediate->usingVulkanMemoryModel() &&
glslangIntermediate->getSpv().spv >= glslang::EShTargetSpv_1_6) {
builder.addDecoration(id, spv::DecorationVolatile);
}