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

Sun Mar 23 04:36:37 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-flang-rhel-clang` running on `ppc64le-flang-rhel-test` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/23310

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
33.513 [232/66/6490] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGFast.cpp.o
33.522 [232/65/6491] Linking CXX static library lib/libclangStaticAnalyzerFrontend.a
33.584 [229/67/6492] Linking CXX executable tools/flang/unittests/Evaluate/real.test
33.606 [229/66/6493] Linking CXX executable tools/flang/unittests/Evaluate/integer.test
33.631 [229/65/6494] Linking CXX executable tools/flang/unittests/Evaluate/logical.test
33.867 [229/64/6495] Linking CXX executable tools/flang/unittests/Evaluate/intrinsics.test
33.884 [229/63/6496] Building CXX object lib/Target/PowerPC/CMakeFiles/LLVMPowerPCCodeGen.dir/PPCCTRLoops.cpp.o
33.900 [229/62/6497] Linking CXX executable tools/flang/unittests/Evaluate/folding.test
33.957 [229/61/6498] Linking CXX executable tools/flang/unittests/Evaluate/expression.test
34.049 [229/60/6499] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o 
ccache /home/buildbots/llvm-external-buildbots/clang.19.1.7/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-flang-rhel-test/ppc64le-flang-rhel-clang-build/build/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/llvm-project/llvm/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/build/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/llvm-project/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/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp
/home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/llvm-project/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());
      |                             ^~~~~~~~~~~~~~~~~
/home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note: passing argument to parameter 'InstrIdxForVirtReg' here
 1021 |     DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
      |                                   ^
1 error generated.
34.062 [229/59/6500] Building CXX object lib/Target/PowerPC/CMakeFiles/LLVMPowerPCCodeGen.dir/PPCCallingConv.cpp.o
34.125 [229/58/6501] Building CXX object lib/Target/PowerPC/CMakeFiles/LLVMPowerPCCodeGen.dir/PPCTargetTransformInfo.cpp.o
34.388 [229/57/6502] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
34.464 [229/56/6503] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineLoopInfo.cpp.o
34.552 [229/55/6504] Building CXX object lib/Target/PowerPC/CMakeFiles/LLVMPowerPCCodeGen.dir/PPCTargetMachine.cpp.o
34.554 [229/54/6505] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WindowScheduler.cpp.o
34.604 [229/53/6506] Building CXX object lib/Target/PowerPC/CMakeFiles/LLVMPowerPCCodeGen.dir/PPCMCInstLower.cpp.o
34.639 [229/52/6507] Linking CXX executable bin/clang-installapi
34.729 [229/51/6508] Linking CXX executable bin/clang-refactor
34.733 [229/50/6509] Linking CXX executable bin/clang-diff
34.751 [229/49/6510] Linking CXX executable bin/diagtool
34.755 [229/48/6511] Linking CXX shared module lib/SampleAnalyzerPlugin.so
34.789 [229/47/6512] Building CXX object tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/ReducerWorkItem.cpp.o
34.856 [229/46/6513] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGDumper.cpp.o
35.089 [229/45/6514] Linking CXX shared module lib/CheckerDependencyHandlingAnalyzerPlugin.so
35.127 [229/44/6515] Linking CXX shared module lib/CheckerOptionHandlingAnalyzerPlugin.so
35.221 [229/43/6516] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocFast.cpp.o
35.610 [229/42/6517] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ShrinkWrap.cpp.o
35.794 [229/41/6518] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
35.810 [229/40/6519] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/InstrEmitter.cpp.o
35.998 [229/39/6520] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RDFGraph.cpp.o
36.222 [229/38/6521] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGRRList.cpp.o
36.264 [229/37/6522] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ScheduleDAGInstrs.cpp.o
36.342 [229/36/6523] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBasicBlock.cpp.o
36.361 [229/35/6524] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/PrologEpilogInserter.cpp.o
36.687 [229/34/6525] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/Utils.cpp.o
36.814 [229/33/6526] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineLICM.cpp.o
36.974 [229/32/6527] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBlockPlacement.cpp.o
37.038 [229/31/6528] Building CXX object lib/Target/PowerPC/CMakeFiles/LLVMPowerPCCodeGen.dir/PPCRegisterInfo.cpp.o
37.192 [229/30/6529] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SplitKit.cpp.o

```

</details>

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