[llvm] [InstCombine][X86] Fold blendv(x, y, shuffle(bitcast(sext(m)))) -> select(shuffle(m),x,y) (PR #96882)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-lld-multistage-test` running on `ppc64le-lld-multistage-test` while building `llvm` at step 12 "build-stage2-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/168/builds/662

Here is the relevant piece of the build log for the reference:
```
Step 12 (build-stage2-unified-tree) failure: build (failure)
...
302.763 [905/440/4816] Building AMDGPUGenPreLegalizeGICombiner.inc...
302.798 [905/439/4817] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64CallingConvention.cpp.o
302.817 [905/438/4818] Building AMDGPUGenDisassemblerTables.inc...
302.822 [905/437/4819] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaPPC.cpp.o
302.830 [905/436/4820] Building CXX object lib/Target/ARM/Disassembler/CMakeFiles/LLVMARMDisassembler.dir/ARMDisassembler.cpp.o
302.858 [904/436/4821] Linking CXX static library lib/libLLVMARMDisassembler.a
302.893 [904/435/4822] Building CXX object lib/Target/XCore/CMakeFiles/LLVMXCoreCodeGen.dir/XCoreTargetMachine.cpp.o
302.904 [903/435/4823] Building AMDGPUGenMCPseudoLowering.inc...
302.925 [903/434/4824] Linking CXX static library lib/libLLVMXCoreCodeGen.a
302.954 [903/433/4825] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstCombineIntrinsic.cpp.o
FAILED: lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstCombineIntrinsic.cpp.o 
ccache /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/install/stage1/bin/clang++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage2/lib/Target/X86 -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/lib/Target/X86 -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/build/stage2/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/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 -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17 -fvisibility=hidden  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstCombineIntrinsic.cpp.o -MF lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstCombineIntrinsic.cpp.o.d -o lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstCombineIntrinsic.cpp.o -c /home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp
/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp:2813:19: error: comparison of integers of different signs: 'int' and 'size_t' (aka 'unsigned long') [-Werror,-Wsign-compare]
 2813 |       if (NumElts < ShuffleMask.size() || !isPowerOf2_32(NumElts) ||
      |           ~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~
1 error generated.
302.975 [903/432/4826] Building CXX object tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CGException.cpp.o
303.053 [903/431/4827] Building AMDGPUGenPostLegalizeGICombiner.inc...
303.102 [903/430/4828] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64StackTaggingPreRA.cpp.o
303.142 [903/429/4829] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaWasm.cpp.o
303.160 [903/428/4830] Building CXX object lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyLowerEmscriptenEHSjLj.cpp.o
303.175 [903/427/4831] Building CXX object tools/clang/lib/Interpreter/CMakeFiles/obj.clangInterpreter.dir/IncrementalParser.cpp.o
303.181 [903/426/4832] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64A57FPLoadBalancing.cpp.o
303.198 [903/425/4833] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/CheckExprLifetime.cpp.o
303.241 [903/424/4834] Building CXX object unittests/ExecutionEngine/Orc/CMakeFiles/OrcJITTests.dir/SharedMemoryMapperTest.cpp.o
303.294 [903/423/4835] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64CollectLOH.cpp.o
303.333 [903/422/4836] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaAccess.cpp.o
303.432 [903/421/4837] Building CXX object tools/clang/unittests/StaticAnalyzer/CMakeFiles/StaticAnalysisTests.dir/Z3CrosscheckOracleTest.cpp.o
303.498 [903/420/4838] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86MCInstLower.cpp.o
303.517 [903/419/4839] Building CXX object unittests/ExecutionEngine/Orc/CMakeFiles/OrcJITTests.dir/RTDyldObjectLinkingLayerTest.cpp.o
303.549 [903/418/4840] Building CXX object lib/Target/WebAssembly/CMakeFiles/LLVMWebAssemblyCodeGen.dir/WebAssemblyISelLowering.cpp.o
303.559 [903/417/4841] Building CXX object tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CGVTables.cpp.o
303.590 [903/416/4842] Building CXX object unittests/Target/VE/CMakeFiles/VETests.dir/MachineInstrTest.cpp.o
303.618 [903/415/4843] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64ExpandPseudoInsts.cpp.o
303.698 [903/414/4844] Building CXX object tools/clang/lib/Driver/CMakeFiles/obj.clangDriver.dir/Driver.cpp.o
303.745 [903/413/4845] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaModule.cpp.o
303.746 [903/412/4846] Building CXX object lib/Target/ARM/CMakeFiles/LLVMARMCodeGen.dir/ARMISelDAGToDAG.cpp.o
303.751 [903/411/4847] Building CXX object tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CGBlocks.cpp.o
303.753 [903/410/4848] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86PreTileConfig.cpp.o
303.797 [903/409/4849] Building CXX object tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/ItaniumCXXABI.cpp.o
303.970 [903/408/4850] Building AMDGPUGenSubtargetInfo.inc...
303.997 [903/407/4851] Building CXX object tools/clang/lib/Index/CMakeFiles/obj.clangIndex.dir/USRGeneration.cpp.o
304.000 [903/406/4852] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86CallingConv.cpp.o
304.027 [903/405/4853] Building RISCVGenDAGISel.inc...
304.040 [903/404/4854] Building CXX object lib/Target/ARM/CMakeFiles/LLVMARMCodeGen.dir/ARMInstructionSelector.cpp.o
304.067 [903/403/4855] Building CXX object unittests/Target/AArch64/CMakeFiles/AArch64Tests.dir/MatrixRegisterAliasing.cpp.o
304.213 [903/402/4856] Building CXX object tools/clang/lib/Serialization/CMakeFiles/obj.clangSerialization.dir/ASTWriterDecl.cpp.o
304.226 [903/401/4857] Building CXX object tools/clang/lib/AST/CMakeFiles/obj.clangAST.dir/Stmt.cpp.o
304.286 [903/400/4858] Building CXX object tools/clang/lib/Serialization/CMakeFiles/obj.clangSerialization.dir/ASTWriterStmt.cpp.o

```

https://github.com/llvm/llvm-project/pull/96882