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

Sun Mar 23 04:29:47 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `llvm` at step 4 "build stage 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/14264

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

```
Step 4 (build stage 1) failure: 'ninja' (failure)
...
[74/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/StackSlotColoring.cpp.o
[75/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TailDuplicator.cpp.o
[76/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ShrinkWrap.cpp.o
[77/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineScheduler.cpp.o
[78/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineOutliner.cpp.o
[79/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetRegisterInfo.cpp.o
[80/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineSink.cpp.o
[81/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineVerifier.cpp.o
[82/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocGreedy.cpp.o
[83/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o 
/usr/local/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/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/CodeGen -I/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/llvm/lib/CodeGen -I/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/include -I/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -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  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -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/tcwg-buildbot/worker/clang-aarch64-quick/llvm/llvm/lib/CodeGen/TargetInstrInfo.cpp
../llvm/llvm/lib/CodeGen/TargetInstrInfo.cpp:1514:29: error: non-const lvalue reference to type 'DenseMap<unsigned int, [...]>' cannot bind to a value of unrelated type 'DenseMap<Register, [...]>'
 1514 |                             InstIdxForVirtReg, Root.getOperand(0).getReg());
      |                             ^~~~~~~~~~~~~~~~~
../llvm/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note: passing argument to parameter 'InstrIdxForVirtReg' here
 1021 |     DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
      |                                   ^
1 error generated.
[84/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SplitKit.cpp.o
[85/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VirtRegMap.cpp.o
[86/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineCycleAnalysis.cpp.o
[87/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VLIWMachineScheduler.cpp.o
[88/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/XRayInstrumentation.cpp.o
[89/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGVLIW.cpp.o
[90/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachinePipeliner.cpp.o
[91/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGFast.cpp.o
[92/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/UnreachableBlockElim.cpp.o
[93/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
[94/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ScheduleDAGInstrs.cpp.o
[95/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegisterCoalescer.cpp.o
[96/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
[97/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WindowScheduler.cpp.o
[98/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGRRList.cpp.o
[99/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/InstrEmitter.cpp.o
[100/309] Building CXX object lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
[101/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGDumper.cpp.o
[102/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGSDNodes.cpp.o
[103/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FastISel.cpp.o
[104/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ResourcePriorityQueue.cpp.o
[105/309] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/Utils.cpp.o
[106/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/PrologEpilogInserter.cpp.o
[107/309] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
[108/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/VarLocBasedImpl.cpp.o
[109/309] Building CXX object lib/CodeGen/MIRParser/CMakeFiles/LLVMMIRParser.dir/MIParser.cpp.o
[110/309] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o
[111/309] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGISel.cpp.o
[112/309] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/IRTranslator.cpp.o
[113/309] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/InstrRefBasedImpl.cpp.o

```

</details>

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