Using MSAA UAV store instruction (introduced in SM6.7) with a innocuous write-mask results in an AV in dxc.

[agrewal-nv]

Description
Using MSAA UAV store instruction (introduced in SM6.7) with a innocuous write-mask results in an AV in dxc.

Steps to Reproduce
Compile shader like:

RWTexture2DMS<float4, 4> uavMsaaTex : register(u0);

[numthreads(1, 1, 1)]
void mainMsaa(uint3 DTid : SV_DispatchThreadID)
{
    uavMsaaTex.sample[0][uint2(0,0)].xyzw = float4(0, 0, 0, 0);
}

dxc -T cs_6_7 -E mainMsaa uavMsaa.hlsl

It succeeds if you remove the .xyzw write mask (or use the non-sample suffix operator).

See https://godbolt.org/z/zzndfzd8K (uncomment the failing line)

Actual Behavior
AV with this stack:

0:000> k
 # Child-SP          RetAddr               Call Site
00 00000022`7d98aa00 00007ff8`cdd9736b     dxcompiler!llvm::DataLayout::getPointerTypeSizeInBits+0x6
01 00000022`7d98aa30 00007ff8`cdc8749f     dxcompiler!llvm::getOrEnforceKnownAlignment+0x37
02 00000022`7d98aac0 00007ff8`cdc3eea7     dxcompiler!llvm::InstCombiner::visitStoreInst+0xa7
03 00000022`7d98ab50 00007ff8`cdc3e0af     dxcompiler!llvm::InstCombiner::run+0x2bb
04 00000022`7d98abd0 00007ff8`cdc3f175     dxcompiler!combineInstructionsOverFunction+0x237
05 00000022`7d98af30 00007ff8`ce7379d8     dxcompiler!`anonymous namespace'::InstructionCombiningPass::runOnFunction+0xc5
06 00000022`7d98af90 00007ff8`ce737b40     dxcompiler!llvm::FPPassManager::runOnFunction+0x194
07 00000022`7d98b090 00007ff8`ce737d4b     dxcompiler!llvm::FPPassManager::runOnModule+0x90
08 00000022`7d98b0f0 00007ff8`ce737579     dxcompiler!`anonymous namespace'::MPPassManager::runOnModule+0x1d7
09 00000022`7d98b1e0 00007ff8`cddd985c     dxcompiler!llvm::legacy::PassManagerImpl::run+0x95
0a 00000022`7d98b220 00007ff8`cddd9bc8     dxcompiler!`anonymous namespace'::EmitAssemblyHelper::EmitAssembly+0x430
0b 00000022`7d98b2b0 00007ff8`cddcf6ad     dxcompiler!clang::EmitBackendOutput+0x2fc
0c 00000022`7d98b510 00007ff8`ce461888     dxcompiler!clang::BackendConsumer::HandleTranslationUnit+0x1bd
0d 00000022`7d98b5e0 00007ff8`cdec3c47     dxcompiler!clang::ParseAST+0x1f8
0e 00000022`7d98b690 00007ff8`cddcef71     dxcompiler!clang::ASTFrontendAction::ExecuteAction+0x97
0f 00000022`7d98b6c0 00007ff8`cdec3b95     dxcompiler!clang::CodeGenAction::ExecuteAction+0x481
10 00000022`7d98b920 00007ff8`cda90b5c     dxcompiler!clang::FrontendAction::Execute+0x51
11 00000022`7d98b950 00007ff8`cda97e9d     dxcompiler!DxcCompiler::Compile+0x331c
12 00000022`7d98e0d0 00007ff8`cda9363e     dxcompiler!hlsl::DxcCompilerAdapter::WrapCompile+0x69d
13 00000022`7d98ef50 00007ff8`cda93527     dxcompiler!hlsl::DxcCompilerAdapter::CompileWithDebug+0xfe
14 00000022`7d98efd0 00007ff7`462f5276     dxcompiler!hlsl::DxcCompilerAdapter::Compile+0x97
15 00000022`7d98f050 00007ff7`462fbf43     dxc_full+0x5276
16 00000022`7d98f280 00007ff7`46310de8     dxc_full+0xbf43
17 00000022`7d98fea0 00007ffa`56bbe8d7     dxc_full+0x20de8
18 00000022`7d98fee0 00007ffa`578fc34c     KERNEL32!BaseThreadInitThunk+0x17
19 00000022`7d98ff10 00000000`00000000     ntdll!RtlUserThreadStart+0x2c
0:000> r
rax=0000000000000004 rbx=00000134885a4820 rcx=00000134885a4820
rdx=0000001000000000 rsi=00000134885bc030 rdi=0000013489f98e88
rip=00007ff8cdaf12d2 rsp=000000227d98aa00 rbp=000000227d98aa90
 r8=00000134885a4820  r9=0000013489f66570 r10=00000134885a4870
r11=00000000ffffffff r12=0000013489f66570 r13=0000000000000004
r14=00000134885a4820 r15=0000013489f6bd68
iopl=0         nv up ei pl nz na po nc
cs=0033  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010206
dxcompiler!llvm::DataLayout::getPointerTypeSizeInBits+0x6:
00007ff8`cdaf12d2 807a080e        cmp     byte ptr [rdx+8],0Eh ds:00000010`00000008=??

Environment

• DXC version: 1.8.2505 +
• Host Operating System: Win11