[SPIR-V] Silent crash when using any WaveMultiPrefix* intrinsic with first arg of type uint*

[Dredhog]

Title

[SPIR-V] Silent crash when using any WaveMultiPrefix* intrinsic with first arg of type uint*

Minimal repro steps

1. Compile repro_shader.txt with dxc.exe -E main -T ps_6_5 -spirv repro_shader.txt

StructuredBuffer<uint4> g_mask;

uint4 main(uint input : ATTR0) : SV_Target {
    uint4 mask = g_mask[0];

    uint4 res = uint4(0,0,0,0);
    res += WaveMultiPrefixBitAnd(input, mask);
    res += WaveMultiPrefixBitOr(input, mask);
    res += WaveMultiPrefixBitXor(input, mask);
    res += WaveMultiPrefixProduct(input, mask);
    res += WaveMultiPrefixSum(input, mask);

    //res += WaveMultiPrefixBitAnd((int4)input, mask);	// error: WaveMultiPrefixBitAnd intrinsic function unimplemented
    //res += WaveMultiPrefixBitOr((int4)input, mask);   // error: WaveMultiPrefixBitOr intrinsic function unimplemented
    //res += WaveMultiPrefixBitXor((int4), mask);       // error: WaveMultiPrefixBitXor intrinsic function unimplemented
    //res += WaveMultiPrefixProduct((int4)input, mask); // error: WaveMultiPrefixProduct intrinsic function unimplemented
    //res += WaveMultiPrefixSum((int4)input, mask);     // error: WaveMultiPrefixSum intrinsic function unimplemented

    return res;
}

Expected result

Output is generated successfully as when using the DXIL backend. If certain wave ops are not yet supported in the SPIR-V backend - error messages explaining lack of wave intrinsic support are printed for the user.

Actual result

Compiler crashes with nothing printed to stdout. Running with a debugger attached the crash is caused by a NULL ptr dereference at:

dxcompiler.dll!clang::spirv::SpirvInstruction::isRelaxedPrecision() Line 165
	at c:\repos\dxc\tools\clang\include\clang\spirv\spirvinstruction.h(165)
dxcompiler.dll!clang::spirv::SpirvEmitter::processBinaryOp(const clang::Expr * lhs, const clang::Expr * rhs, clang::BinaryOperatorKind opcode, clang::QualType computationType, clang::QualType resultType, clang::SourceRange sourceRange, clang::SourceLocation loc, clang::spirv::SpirvInstruction * * lhsInfo, spv::Op mandateGenOpcode) Line 5495
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(5495)
dxcompiler.dll!clang::spirv::SpirvEmitter::doCompoundAssignOperator(const clang::CompoundAssignOperator * expr) Line 2740
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(2740)
dxcompiler.dll!clang::spirv::SpirvEmitter::doExpr(const clang::Expr * expr) Line 819
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(819)
dxcompiler.dll!clang::spirv::SpirvEmitter::doStmt(const clang::Stmt * stmt, llvm::ArrayRef<clang::Attr const *> attrs) Line 781
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(781)
dxcompiler.dll!clang::spirv::SpirvEmitter::doStmt(const clang::Stmt * stmt, llvm::ArrayRef<clang::Attr const *> attrs) Line 752
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(752)
dxcompiler.dll!clang::spirv::SpirvEmitter::doFunctionDecl(const clang::FunctionDecl * decl) Line 1071
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(1071)
dxcompiler.dll!clang::spirv::SpirvEmitter::doDecl(const clang::Decl * decl) Line 735
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(735)
dxcompiler.dll!clang::spirv::SpirvEmitter::HandleTranslationUnit(clang::ASTContext & context) Line 617
	at c:\repos\dxc\tools\clang\lib\spirv\spirvemitter.cpp(617)
dxcompiler.dll!clang::ParseAST(clang::Sema & S, bool PrintStats, bool SkipFunctionBodies) Line 162
	at c:\repos\dxc\tools\clang\lib\parse\parseast.cpp(162)
dxcompiler.dll!clang::ASTFrontendAction::ExecuteAction() Line 556
	at c:\repos\dxc\tools\clang\lib\frontend\frontendaction.cpp(556)
dxcompiler.dll!clang::FrontendAction::Execute() Line 468
	at c:\repos\dxc\tools\clang\lib\frontend\frontendaction.cpp(468)
dxcompiler.dll!DxcCompiler::Compile(const DxcBuffer * pSource, const wchar_t * * pArguments, unsigned int argCount, IDxcIncludeHandler * pIncludeHandler, const _GUID & riid, void * * ppResult) Line 754
	at c:\repos\dxc\tools\clang\tools\dxcompiler\dxcompilerobj.cpp(754)
dxcompiler.dll!hlsl::DxcCompilerAdapter::WrapCompile(int bPreprocess, IDxcBlob * pSource, const wchar_t * pSourceName, const wchar_t * pEntryPoint, const wchar_t * pTargetProfile, const wchar_t * * pArguments, unsigned int argCount, const DxcDefine * pDefines, unsigned int defineCount, IDxcIncludeHandler * pIncludeHandler, IDxcOperationResult * * ppResult, wchar_t * * ppDebugBlobName, IDxcBlob * * ppDebugBlob) Line 1389
	at c:\repos\dxc\tools\clang\tools\dxcompiler\dxcompilerobj.cpp(1389)
dxcompiler.dll!hlsl::DxcCompilerAdapter::CompileWithDebug(IDxcBlob * pSource, const wchar_t * pSourceName, const wchar_t * pEntryPoint, const wchar_t * pTargetProfile, const wchar_t * * pArguments, unsigned int argCount, const DxcDefine * pDefines, unsigned int defineCount, IDxcIncludeHandler * pIncludeHandler, IDxcOperationResult * * ppResult, wchar_t * * ppDebugBlobName, IDxcBlob * * ppDebugBlob) Line 1303
	at c:\repos\dxc\tools\clang\tools\dxcompiler\dxcompilerobj.cpp(1303)
dxcompiler.dll!hlsl::DxcCompilerAdapter::Compile(IDxcBlob * pSource, const wchar_t * pSourceName, const wchar_t * pEntryPoint, const wchar_t * pTargetProfile, const wchar_t * * pArguments, unsigned int argCount, const DxcDefine * pDefines, unsigned int defineCount, IDxcIncludeHandler * pIncludeHandler, IDxcOperationResult * * ppResult) Line 72
	at c:\repos\dxc\tools\clang\tools\dxcompiler\dxcompileradapter.h(72)
dxc.exe!DxcContext::Compile() Line 802
	at c:\repos\dxc\tools\clang\tools\dxclib\dxc.cpp(802)
dxc.exe!dxc::main(int argc, const wchar_t * * argv_) Line 1262
	at c:\repos\dxc\tools\clang\tools\dxclib\dxc.cpp(1262)
dxc.exe!wmain(int argc, const wchar_t * * argv_) Line 22
	at c:\repos\dxc\tools\clang\tools\dxc\dxcmain.cpp(22)
dxc.exe!invoke_main() Line 91
	at d:\agent\_work\2\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl(91)
dxc.exe!__scrt_common_main_seh() Line 288
	at d:\agent\_work\2\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl(288)
dxc.exe!__scrt_common_main() Line 331
	at d:\agent\_work\2\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl(331)
dxc.exe!wmainCRTStartup() Line 17
	at d:\agent\_work\2\s\src\vctools\crt\vcstartup\src\startup\exe_wmain.cpp(17)
kernel32.dll!00007ffbb5ab7974()
ntdll.dll!00007ffbb733a271()

Further technical details

Seems that only unit scalars and vectors passed as first arguments to these wave intrinsic will trigger the crash e.g. casting with (int4) as seen in the comments will print errors as expected but if any of the uncommented lines are not removed first - the crash will silence the error message.

The repro shader is based on sm_6_5_wave.hlsl from the DXC repo so this issue might be known internally I but couldn't find a bug report for it.

some lines which don't trigger the crash by themselves were removed, however, the crash still happens on the original file.

[ehsannas]

Thanks for reporting. Will investigate.

[ehsannas]

Yeah we have started the work for SPIR-V support for sm_6_5, but it's not 100% done yet.
I'm not quite sure whether there currently exists Vulkan/SPIR-V equivalent features for WaveMultiPrefix*?

[ehsannas]

(As for the crash, I've put up a PR to fix it and show a proper error message).

[Dredhog]

I'm not quite sure whether there currently exists Vulkan/SPIR-V equivalent features for WaveMultiPrefix*?

Not sure, was actually trying to figure that out by compiling the actual shaders :)

(As for the crash, I've put up a PR to fix it and show a proper error message).

Sounds good! 👍