Add a pass to collect dropped var stats for MIR

[rastogishubham]

This patch uses the DroppedVariableStats class to add dropped variable statistics for MIR passes.

Reland 1c082c9

[chapuni]

You should've moved DroppedVariableStats stuff out of llvm/Passes in advance.
At a glance, they don't depend on LLVMPass any more. (#120711)

[chapuni]

It's odd to depend on LLVMPasses here.

[chapuni]

I have reverted this. I could fix them though.

[nikic]

I have already commented on this three times...

#115566 (comment)
#117044 (comment)
#120501 (comment)

...and my feedback still hasn't been addressed.

If you reapply this again without actually addressing the problems with this patch, I will request your commit access to be withdrawn.

[rastogishubham]

@nikic I am very sorry about not addressing the patch issues, I will make sure to not include so much code into MachineFunctionPass.h. I had applied some aggressive filtering in my email and didn't see those comments, but I understand it is not an excuse.

Do you have some recommendations on how to redesign this better to make it so that the build times are smaller?

[rastogishubham]

@chapuni The reason I designed it this way, is because if I move all the class DroppedVariableStats code out of llvm/Passes to codegen, then, the libclang/codegen library fails when linking on clang-ppc64le-linux-multistage

With this error:

/CodeGenModule.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenPGO.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenTBAA.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenTypes.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/ConstantInitBuilder.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CoverageMappingGen.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/ItaniumCXXABI.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/LinkInModulesPass.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/MacroPPCallbacks.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/MicrosoftCXXABI.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/ModuleBuilder.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/ObjectFilePCHContainerWriter.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/PatternInit.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/SanitizerMetadata.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/SwiftCallingConv.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/TargetInfo.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/AArch64.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/AMDGPU.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/ARC.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/ARM.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/AVR.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/BPF.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/CSKY.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/DirectX.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/Hexagon.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/Lanai.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/LoongArch.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/M68k.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/MSP430.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/Mips.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/NVPTX.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/PNaCl.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/PPC.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/RISCV.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/SPIR.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/Sparc.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/SystemZ.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/TCE.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/VE.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/WebAssembly.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/X86.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/Targets/XCore.cpp.o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/VarBypassDetector.cpp.o  -Wl,-rpath,"\$ORIGIN/../lib:/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/lib:"  lib/libclangFrontend.so.20.0git  lib/libclangSerialization.so.20.0git  lib/libLLVMCoverage.so.20.0git  lib/libLLVMFrontendDriver.so.20.0git  lib/libLLVMLTO.so.20.0git  lib/libLLVMPasses.so.20.0git  lib/libclangAnalysis.so.20.0git  lib/libLLVMFrontendHLSL.so.20.0git  lib/libclangAST.so.20.0git  lib/libclangLex.so.20.0git  lib/libclangBasic.so.20.0git  lib/libLLVMExtensions.so.20.0git  lib/libLLVMCoroutines.so.20.0git  lib/libLLVMHipStdPar.so.20.0git  lib/libLLVMipo.so.20.0git  lib/libLLVMFrontendOpenMP.so.20.0git  lib/libLLVMFrontendOffloading.so.20.0git  lib/libLLVMLinker.so.20.0git  lib/libLLVMIRPrinter.so.20.0git  lib/libLLVMInstrumentation.so.20.0git  lib/libLLVMCodeGenTypes.so.20.0git  lib
libLLVMObjCARCOpts.so.20.0git  lib/libLLVMScalarOpts.so.20.0git  lib/libLLVMAggressiveInstCombine.so.20.0git  lib/libLLVMInstCombine.so.20.0git  lib/libLLVMTarget.so.20.0git  lib/libLLVMTransformUtils.so.20.0git  lib/libLLVMBitWriter.so.20.0git  lib/libLLVMAnalysis.so.20.0git  lib/libLLVMProfileData.so.20.0git  lib/libLLVMObject.so.20.0git  lib/libLLVMIRReader.so.20.0git  lib/libLLVMBitReader.so.20.0git  lib/libLLVMCore.so.20.0git  lib/libLLVMMC.so.20.0git  lib/libLLVMTargetParser.so.20.0git  lib/libLLVMSupport.so.20.0git  lib/libLLVMDemangle.so.20.0git  -Wl,-rpath-link,/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/lib && :
tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/BackendUtil.cpp.o:(.toc+0x258): undefined reference to `vtable for llvm::DroppedVariableStatsIR'

This is because libclang/codegen doesn't link against libllvm/codegen however, it does link against libllvm/passes. If I cannot have libllvm/codegen not link against passes, then I am unsure of where I can put the code so that I can calculate dropped statistics for both IR and MIR.

Do you have an idea of what could be done?

[llvm-ci]

LLVM Buildbot has detected a new failure on builder lld-x86_64-win running on as-worker-93 while building llvm at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/146/builds/1904

Here is the relevant piece of the build log for the reference

Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM-Unit :: Support/./SupportTests.exe/38/87' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:C:\a\lld-x86_64-win\build\unittests\Support\.\SupportTests.exe-LLVM-Unit-17800-38-87.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=87 GTEST_SHARD_INDEX=38 C:\a\lld-x86_64-win\build\unittests\Support\.\SupportTests.exe
--

Script:
--
C:\a\lld-x86_64-win\build\unittests\Support\.\SupportTests.exe --gtest_filter=ProgramEnvTest.CreateProcessLongPath
--
C:\a\lld-x86_64-win\llvm-project\llvm\unittests\Support\ProgramTest.cpp(160): error: Expected equality of these values:
  0
  RC
    Which is: -2

C:\a\lld-x86_64-win\llvm-project\llvm\unittests\Support\ProgramTest.cpp(163): error: fs::remove(Twine(LongPath)): did not return errc::success.
error number: 13
error message: permission denied



C:\a\lld-x86_64-win\llvm-project\llvm\unittests\Support\ProgramTest.cpp:160
Expected equality of these values:
  0
  RC
    Which is: -2

C:\a\lld-x86_64-win\llvm-project\llvm\unittests\Support\ProgramTest.cpp:163
fs::remove(Twine(LongPath)): did not return errc::success.
error number: 13
error message: permission denied




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