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

Sun Mar 23 04:29:08 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-nvptx64-nvidia-ubuntu` running on `as-builder-7` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/160/builds/15214

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/cmake/Modules/../../libc/src/stdio/printf_core/strerror_converter.h:15,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/cmake/Modules/../../libc/src/stdio/printf_core/converter.h:15,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/cmake/Modules/../../libc/src/__support/RPC/rpc_server.h:43,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/cmake/Modules/../../libc/shared/rpc_server.h:12,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/tools/llvm-gpu-loader/server.h:19,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/tools/llvm-gpu-loader/nvptx.cpp:17:
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/cmake/Modules/../../libc/src/stdio/printf_core/writer.h:55:30: warning: ‘maybe_unused’ attribute ignored [-Wattributes]
   55 |   [[maybe_unused]] WriteMode write_mode_;
      |                              ^~~~~~~~~~~
44.583 [692/39/1995] 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 -DLLVM_EXPORTS -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/llvm-nvptx64-nvidia-ubuntu/build/lib/CodeGen -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/lib/CodeGen -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/include -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/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 -fPIC  -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/llvm-nvptx64-nvidia-ubuntu/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/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:64,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/include/llvm/Support/PGOOptions.h:17,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/include/llvm/Target/TargetMachine.h:24,
                 from /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:38:
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/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/llvm-nvptx64-nvidia-ubuntu/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/llvm-nvptx64-nvidia-ubuntu/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/llvm-nvptx64-nvidia-ubuntu/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,
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
47.594 [692/15/2019] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FastISel.cpp.o
48.541 [692/13/2021] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MIRPrinter.cpp.o
48.910 [692/12/2022] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBlockPlacement.cpp.o
49.835 [692/11/2023] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/VarLocBasedImpl.cpp.o
51.709 [692/10/2024] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o
52.346 [692/9/2025] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGISel.cpp.o
52.947 [692/8/2026] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/AsmPrinter.cpp.o
53.112 [692/7/2027] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/IRTranslator.cpp.o
53.424 [692/6/2028] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachinePipeliner.cpp.o
53.670 [692/5/2029] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/DwarfDebug.cpp.o
53.910 [692/4/2030] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/CombinerHelper.cpp.o
54.747 [692/3/2031] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/InstrRefBasedImpl.cpp.o
55.209 [692/2/2032] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
60.531 [692/1/2033] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGBuilder.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

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