[llvm] [AArch64][MachineCombiner] Reassociate long chains of accumulation instructions into a tree to increase ILP (PR #126060)

Sun Mar 23 04:41:16 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-runtime-cuda-clang` running on `as-builder-7` while building `llvm` at step 7 "build-clang-default".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/7/builds/12581

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

```
Step 7 (build-clang-default) failure: cmake (failure)
...
22.701 [661/130/4149] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CIndexCXX.cpp.o
22.734 [660/130/4150] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXCompilationDatabase.cpp.o
22.786 [659/130/4151] Linking CXX static library lib/libLLVMX86Desc.a
22.809 [658/130/4152] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXLoadedDiagnostic.cpp.o
22.900 [657/130/4153] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/InlineSpiller.cpp.o
22.930 [656/130/4154] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
23.066 [655/130/4155] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
23.205 [654/130/4156] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CIndexer.cpp.o
23.219 [653/130/4157] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/FatalErrorHandler.cpp.o
23.264 [652/130/4158] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/c++ -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/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/build/clang/lib/CodeGen -I/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen -I/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/build/clang/include -I/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -std=c++17 -MD -MT lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o -c /home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp
In file included from /usr/include/c++/11/cassert:44,
                 from /home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:64,
                 from /home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/include/llvm/Support/PGOOptions.h:17,
                 from /home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/include/llvm/Target/TargetMachine.h:24,
                 from /home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:38:
/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp: In member function ‘virtual void llvm::TargetInstrInfo::genAlternativeCodeSequence(llvm::MachineInstr&, unsigned int, llvm::SmallVectorImpl<llvm::MachineInstr*>&, llvm::SmallVectorImpl<llvm::MachineInstr*>&, llvm::DenseMap<llvm::Register, unsigned int>&) const’:
/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1487:46: warning: comparison of unsigned expression in ‘>= 0’ is always true [-Wtype-limits]
 1487 |         assert(IndexedReg.index() - MaxWidth >= 0);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1514:29: error: cannot convert ‘llvm::DenseMap<llvm::Register, unsigned int>’ to ‘llvm::DenseMap<unsigned int, unsigned int>&’
 1514 |                             InstIdxForVirtReg, Root.getOperand(0).getReg());
      |                             ^~~~~~~~~~~~~~~~~
      |                             |
      |                             llvm::DenseMap<llvm::Register, unsigned int>
/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-clang/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note:   initializing argument 6 of ‘void llvm::TargetInstrInfo::reduceAccumulatorTree(llvm::SmallVectorImpl<llvm::Register>&, llvm::SmallVectorImpl<llvm::MachineInstr*>&, llvm::MachineFunction&, llvm::MachineInstr&, llvm::MachineRegisterInfo&, llvm::DenseMap<unsigned int, unsigned int>&, llvm::Register) const’
 1021 |     DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
23.297 [652/129/4159] Building CXX object tools/clang/tools/driver/CMakeFiles/clang.dir/cc1as_main.cpp.o
23.326 [652/128/4160] Building CXX object tools/clang/tools/driver/CMakeFiles/clang.dir/cc1gen_reproducer_main.cpp.o
23.417 [652/127/4161] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/Analysis.cpp.o
23.632 [652/126/4162] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/BranchFolding.cpp.o
23.645 [652/125/4163] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/FixupStatepointCallerSaved.cpp.o
23.659 [652/124/4164] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXType.cpp.o
23.782 [652/123/4165] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXCursor.cpp.o
23.846 [652/122/4166] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXIndexDataConsumer.cpp.o
23.850 [652/121/4167] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXSourceLocation.cpp.o
23.852 [652/120/4168] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGRRList.cpp.o
23.918 [652/119/4169] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXString.cpp.o
23.958 [652/118/4170] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RDFGraph.cpp.o
23.990 [652/117/4171] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXStoredDiagnostic.cpp.o
23.992 [652/116/4172] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
24.039 [652/115/4173] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/Rewrite.cpp.o
24.043 [652/114/4174] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CIndexDiagnostic.cpp.o
24.082 [652/113/4175] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CIndexUSRs.cpp.o
24.087 [652/112/4176] Building CXX object tools/clang/tools/clang-check/CMakeFiles/clang-check.dir/ClangCheck.cpp.o
24.105 [652/111/4177] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXComment.cpp.o
24.204 [652/110/4178] Building CXX object tools/clang/tools/c-index-test/CMakeFiles/c-index-test.dir/core_main.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/126060