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

Sun Mar 23 04:33:54 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-clang-x86_64-linux-debian` running on `gribozavr4` while building `llvm` at step 5 "compile-openmp".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/6/builds/7722

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

```
Step 5 (compile-openmp) failure: build (failure)
...
19.009 [2357/96/3046] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/XRayInstrumentation.cpp.o
19.270 [2356/96/3047] Building AMDGPUGenDisassemblerTables.inc...
19.417 [2355/96/3048] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MIRPrinter.cpp.o
19.539 [2354/96/3049] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VirtRegMap.cpp.o
19.572 [2353/96/3050] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/StackSlotColoring.cpp.o
19.694 [2352/96/3051] Building AMDGPUGenSearchableTables.inc...
19.887 [2351/96/3052] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineFunction.cpp.o
19.990 [2350/96/3053] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBasicBlock.cpp.o
20.364 [2349/96/3054] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetRegisterInfo.cpp.o
20.512 [2348/96/3055] 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/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/b/1/openmp-clang-x86_64-linux-debian/llvm.build/lib/CodeGen -I/b/1/openmp-clang-x86_64-linux-debian/llvm.src/llvm/lib/CodeGen -I/b/1/openmp-clang-x86_64-linux-debian/llvm.build/include -I/b/1/openmp-clang-x86_64-linux-debian/llvm.src/llvm/include -fPIC -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  -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 /b/1/openmp-clang-x86_64-linux-debian/llvm.src/llvm/lib/CodeGen/TargetInstrInfo.cpp
/b/1/openmp-clang-x86_64-linux-debian/llvm.src/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<llvm::Register, [...]>'
                            InstIdxForVirtReg, Root.getOperand(0).getReg());
                            ^~~~~~~~~~~~~~~~~
/b/1/openmp-clang-x86_64-linux-debian/llvm.src/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note: passing argument to parameter 'InstrIdxForVirtReg' here
    DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
                                  ^
1 error generated.
20.578 [2348/95/3056] Building RISCVGenDAGISel.inc...
20.606 [2348/94/3057] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TailDuplicator.cpp.o
20.802 [2348/93/3058] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ScheduleDAGInstrs.cpp.o
20.819 [2348/92/3059] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineVerifier.cpp.o
20.928 [2348/91/3060] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ResourcePriorityQueue.cpp.o
20.941 [2348/90/3061] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ShrinkWrap.cpp.o
20.993 [2348/89/3062] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGFast.cpp.o
21.447 [2348/88/3063] Building CXX object lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
21.575 [2348/87/3064] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o
21.817 [2348/86/3065] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VLIWMachineScheduler.cpp.o
21.949 [2348/85/3066] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBlockPlacement.cpp.o
22.105 [2348/84/3067] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZShortenInst.cpp.o
22.599 [2348/83/3068] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocGreedy.cpp.o
22.631 [2348/82/3069] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegisterCoalescer.cpp.o
22.688 [2348/81/3070] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
22.803 [2348/80/3071] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SplitKit.cpp.o
22.815 [2348/79/3072] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZPostRewrite.cpp.o
22.996 [2348/78/3073] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZSelectionDAGInfo.cpp.o
23.187 [2348/77/3074] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGDumper.cpp.o
23.282 [2348/76/3075] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZLongBranch.cpp.o
23.393 [2348/75/3076] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGRRList.cpp.o
23.447 [2348/74/3077] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZMachineScheduler.cpp.o
23.474 [2348/73/3078] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZLDCleanup.cpp.o
23.521 [2348/72/3079] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/InstrEmitter.cpp.o
23.573 [2348/71/3080] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
23.625 [2348/70/3081] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineSink.cpp.o
23.633 [2348/69/3082] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
23.776 [2348/68/3083] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZSubtarget.cpp.o
23.859 [2348/67/3084] Building CXX object lib/Target/SystemZ/CMakeFiles/LLVMSystemZCodeGen.dir/SystemZMCInstLower.cpp.o
23.905 [2348/66/3085] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineScheduler.cpp.o

```

</details>

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