[llvm] [WebAssembly] Don't stackify multi-def instructions (PR #200429)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `release-noassertions-warnings` running on `google-integrate-b2` while building `llvm` at step 6 "build-default".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/228/builds/1332

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (build-default) failure: cmake (failure)
...
39.354 [4526/34/4027] Building WasmSSAOps.h.inc...
39.355 [4525/34/4028] Building SymbolInterfaces.cpp.inc...
39.355 [4524/34/4029] Building SymbolInterfaces.h.inc...
39.360 [4523/34/4030] Building RegionKindInterface.cpp.inc...
39.366 [4522/34/4031] Building RegionKindInterface.h.inc...
39.367 [4521/34/4032] Building XeGPUTransformOps.cpp.inc...
39.367 [4520/34/4033] Building QuantStorageTypeInterface.cpp.inc...
39.369 [4519/34/4034] Building SymbolInterfacesAttrInterface.cpp.inc...
39.375 [4518/34/4035] Building XeGPUTransformOps.h.inc...
39.378 [4517/34/4036] Building CXX object lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyRegStackify.cpp.o
FAILED: lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyRegStackify.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /usr/bin/ccache /usr/bin/c++ -D_GLIBCXX_USE_CXX11_ABI=1 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/release-noassertions-warnings-build/build/lib/Target/WebAssembly -I/b/release-noassertions-warnings-build/llvm-project/llvm/lib/Target/WebAssembly -I/b/release-noassertions-warnings-build/build/include -I/b/release-noassertions-warnings-build/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Xclang -fno-pch-timestamp -O3 -DNDEBUG -std=c++17 -fvisibility=hidden -fno-exceptions -funwind-tables -fno-rtti -Winvalid-pch -Xclang -include-pch -Xclang /b/release-noassertions-warnings-build/build/lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/cmake_pch.hxx.pch -Xclang -include -Xclang /b/release-noassertions-warnings-build/build/lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/cmake_pch.hxx -MD -MT lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyRegStackify.cpp.o -MF lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyRegStackify.cpp.o.d -o lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyRegStackify.cpp.o -c /b/release-noassertions-warnings-build/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
/b/release-noassertions-warnings-build/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp:354:23: error: unused variable 'UseI' [-Werror,-Wunused-variable]
  354 |   const MachineInstr *UseI = Use->getParent();
      |                       ^~~~
1 error generated.
39.378 [4517/33/4037] Building SymbolInterfacesAttrInterface.h.inc...
39.380 [4517/32/4038] Building QuantStorageTypeInterface.h.inc...
39.380 [4517/31/4039] Building XeGPUEnums.cpp.inc...
39.381 [4517/30/4040] Building OpAsmAttrInterface.cpp.inc...
39.385 [4517/29/4041] Building X86.h.inc...
39.388 [4517/28/4042] Building X86Types.cpp.inc...
39.388 [4517/27/4043] Building OpAsmAttrInterface.h.inc...
39.390 [4517/26/4044] Building OpAsmOpInterface.cpp.inc...
39.390 [4517/25/4045] Linking CXX static library lib/libLLVMAnalysis.a
39.391 [4517/24/4046] Building XeGPUEnums.h.inc...
39.394 [4517/23/4047] Building AlignmentAttrInterface.cpp.inc...
39.394 [4517/22/4048] Building OpAsmOpInterface.h.inc...
39.396 [4517/21/4049] Building SPIRVAttrUtils.inc...
39.399 [4517/20/4050] Building OpAsmTypeInterface.h.inc...
39.400 [4517/19/4051] Building AlignmentAttrInterface.h.inc...
39.405 [4517/18/4052] Building CallInterfaces.cpp.inc...
39.406 [4517/17/4053] Building OpAsmTypeInterface.cpp.inc...
39.573 [4517/16/4054] Building X86GenFastISel.inc...
40.408 [4517/15/4055] Building X86GenGlobalISel.inc...
41.935 [4517/14/4056] Building X86GenDAGISel.inc...
42.377 [4517/13/4057] Building RISCVGenDAGISel.inc...
42.681 [4517/12/4058] Building RISCVGenInstrInfo.inc...
44.579 [4517/11/4059] Building RISCVGenGlobalISel.inc...
45.318 [4517/10/4060] Building AMDGPUGenCallingConv.inc...
45.498 [4517/9/4061] Building X86GenSubtargetInfo.inc...
46.318 [4517/8/4062] Building AMDGPUGenAsmWriter.inc...
46.489 [4517/7/4063] Building X86GenInstrInfo.inc...
50.823 [4517/6/4064] Building AMDGPUGenDAGISel.inc...
52.553 [4517/5/4065] Building AMDGPUGenGlobalISel.inc...
53.227 [4517/4/4066] Building AMDGPUGenInstrInfo.inc...
57.229 [4517/3/4067] Building AMDGPUGenAsmMatcher.inc...
59.803 [4517/2/4068] Building AMDGPUGenRegisterInfo.inc...
61.729 [4517/1/4069] Building AMDGPUGenRegisterBank.inc...

```

</details>

https://github.com/llvm/llvm-project/pull/200429