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

Sun Mar 23 04:45:27 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-remote-linux-win` running on `as-builder-10` while building `llvm` at step 8 "build-default".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/197/builds/3060

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

```
Step 8 (build-default) failure: cmake (failure)
...
45.158 [2187/130/3069]Building CXX object tools\clang\lib\Driver\CMakeFiles\obj.clangDriver.dir\Phases.cpp.obj
45.204 [2186/130/3070]Building CXX object tools\clang\tools\diagtool\CMakeFiles\diagtool.dir\FindDiagnosticID.cpp.obj
45.212 [2185/130/3071]Building CXX object tools\clang\lib\Driver\CMakeFiles\obj.clangDriver.dir\OffloadBundler.cpp.obj
45.216 [2184/130/3072]Building CXX object tools\clang\lib\Driver\CMakeFiles\obj.clangDriver.dir\Tool.cpp.obj
45.239 [2183/130/3073]Building CXX object tools\clang\lib\Driver\CMakeFiles\obj.clangDriver.dir\OptionUtils.cpp.obj
45.287 [2182/130/3074]Building CXX object tools\clang\tools\diagtool\CMakeFiles\diagtool.dir\TreeView.cpp.obj
45.479 [2181/130/3075]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\SwiftErrorValueTracking.cpp.obj
45.558 [2180/130/3076]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\SplitKit.cpp.obj
45.607 [2179/130/3077]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\MachineOperand.cpp.obj
45.618 [2178/130/3078]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\TargetInstrInfo.cpp.obj
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.obj 
ccache C:\PROGRA~1\MICROS~1\2022\COMMUN~1\VC\Tools\MSVC\1441~1.341\bin\Hostx64\x64\cl.exe  /nologo /TP -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_GLIBCXX_ASSERTIONS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -IC:\buildbot\as-builder-10\lldb-x-aarch64\build\lib\CodeGen -IC:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\llvm\lib\CodeGen -IC:\buildbot\as-builder-10\lldb-x-aarch64\build\include -IC:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\llvm\include -D__OPTIMIZE__ /Zc:inline /Zc:preprocessor /Zc:__cplusplus /Oi /bigobj /permissive- /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351 -wd4456 -wd4457 -wd4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505 -wd4610 -wd4510 -wd4702 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204 -wd4577 -wd4091 -wd4592 -wd4319 -wd4709 -wd5105 -wd4324 -wd4251 -wd4275 -w14062 -we4238 /Gw /O2 /Ob2  -MD  /EHs-c- /GR- -UNDEBUG -std:c++17 /showIncludes /Folib\CodeGen\CMakeFiles\LLVMCodeGen.dir\TargetInstrInfo.cpp.obj /Fdlib\CodeGen\CMakeFiles\LLVMCodeGen.dir\LLVMCodeGen.pdb /FS -c C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\llvm\lib\CodeGen\TargetInstrInfo.cpp
C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\llvm\lib\CodeGen\TargetInstrInfo.cpp(1513): error C2664: '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::DenseMapInfo<unsigned int,void>,llvm::detail::DenseMapPair<KeyT,ValueT>> &,llvm::Register) const': cannot convert argument 6 from 'llvm::DenseMap<llvm::Register,unsigned int,llvm::DenseMapInfo<llvm::Register,void>,llvm::detail::DenseMapPair<KeyT,ValueT>>' to 'llvm::DenseMap<unsigned int,unsigned int,llvm::DenseMapInfo<unsigned int,void>,llvm::detail::DenseMapPair<KeyT,ValueT>> &'
        with
        [
            KeyT=unsigned int,
            ValueT=unsigned int
        ]
        and
        [
            KeyT=llvm::Register,
            ValueT=unsigned int
        ]
        and
        [
            KeyT=unsigned int,
            ValueT=unsigned int
        ]
C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\llvm\lib\CodeGen\TargetInstrInfo.cpp(1017): note: see declaration of 'llvm::TargetInstrInfo::reduceAccumulatorTree'
C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\llvm\lib\CodeGen\TargetInstrInfo.cpp(1513): note: while trying to match the argument list '(llvm::SmallVector<ValueT,8>, llvm::SmallVectorImpl<llvm::MachineInstr *>, llvm::MachineFunction, llvm::MachineInstr, llvm::MachineRegisterInfo, llvm::DenseMap<llvm::Register,unsigned int,llvm::DenseMapInfo<llvm::Register,void>,llvm::detail::DenseMapPair<KeyT,ValueT>>, llvm::Register)'
        with
        [
            ValueT=llvm::Register
        ]
        and
        [
            KeyT=llvm::Register,
            ValueT=unsigned int
        ]
45.683 [2178/129/3079]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\ModuloSchedule.cpp.obj
45.754 [2178/128/3080]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\MachineBlockPlacement.cpp.obj
45.803 [2178/127/3081]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\UnreachableBlockElim.cpp.obj
45.831 [2178/126/3082]Building CXX object tools\clang\tools\driver\CMakeFiles\clang.dir\cc1gen_reproducer_main.cpp.obj
45.894 [2178/125/3083]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\XRayInstrumentation.cpp.obj
46.079 [2178/124/3084]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\VirtRegMap.cpp.obj
46.197 [2178/123/3085]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\ShrinkWrap.cpp.obj
46.250 [2178/122/3086]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\TargetRegisterInfo.cpp.obj
46.373 [2178/121/3087]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\MIRPrinter.cpp.obj
46.420 [2178/120/3088]Building CXX object lib\CodeGen\CMakeFiles\LLVMCodeGen.dir\ScheduleDAGInstrs.cpp.obj

```

</details>

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