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

Sun Mar 23 04:57:36 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `publish-sphinx-docs` running on `as-worker-4` while building `llvm` at step 5 "build-docs-llvm-html-docs-clang-html-docs-clang...".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/45/builds/10412

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

```
Step 5 (build-docs-llvm-html-docs-clang-html-docs-clang...) failure: build (failure)
...
163.799 [4534/24/716] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ValueTypes.cpp.o
164.097 [4533/24/717] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SplitKit.cpp.o
164.659 [4532/24/718] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetSchedule.cpp.o
164.819 [4531/24/719] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SwiftErrorValueTracking.cpp.o
164.821 [4530/24/720] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SwitchLoweringUtils.cpp.o
164.873 [4529/24/721] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o
165.381 [4528/24/722] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/StackProtector.cpp.o
165.925 [4527/24/723] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TailDuplicator.cpp.o
166.993 [4526/24/724] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetRegisterInfo.cpp.o
167.519 [4525/24/725] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o 
/usr/bin/c++ -DGTEST_HAS_RTTI=0 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/as-worker-4/publish-sphinx-docs/build/lib/CodeGen -I/home/buildbot/as-worker-4/publish-sphinx-docs/llvm-project/llvm/lib/CodeGen -I/home/buildbot/as-worker-4/publish-sphinx-docs/build/include -I/home/buildbot/as-worker-4/publish-sphinx-docs/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 -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -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/as-worker-4/publish-sphinx-docs/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp
/home/buildbot/as-worker-4/publish-sphinx-docs/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/as-worker-4/publish-sphinx-docs/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/as-worker-4/publish-sphinx-docs/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,
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
168.256 [4525/23/726] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/UnreachableBlockElim.cpp.o
168.387 [4525/22/727] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetPassConfig.cpp.o
168.471 [4525/21/728] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetLoweringObjectFileImpl.cpp.o
168.673 [4525/20/729] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WasmEHPrepare.cpp.o
169.498 [4525/19/730] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetLoweringBase.cpp.o
169.519 [4525/18/731] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/LiveDebugValues.cpp.o
170.091 [4525/17/732] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VirtRegMap.cpp.o
171.025 [4525/16/733] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VLIWMachineScheduler.cpp.o
171.092 [4525/15/734] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/XRayInstrumentation.cpp.o
173.402 [4525/14/735] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TypePromotion.cpp.o
173.527 [4525/13/736] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
174.560 [4525/12/737] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WinEHPrepare.cpp.o
175.898 [4525/11/738] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/LegalizeTypesGeneric.cpp.o
176.812 [4525/10/739] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/LegalizeTypes.cpp.o
177.443 [4525/9/740] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/AttributorAttributes.cpp.o
177.733 [4525/8/741] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
178.245 [4525/7/742] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WindowScheduler.cpp.o
179.246 [4525/6/743] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/LegalizeFloatTypes.cpp.o
181.548 [4525/5/744] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FastISel.cpp.o
183.626 [4525/4/745] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/LegalizeIntegerTypes.cpp.o
184.353 [4525/3/746] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/LegalizeDAG.cpp.o
184.696 [4525/2/747] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/VarLocBasedImpl.cpp.o
196.322 [4525/1/748] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/InstrRefBasedImpl.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

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