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

Sun Mar 23 04:39:21 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `premerge-monolithic-linux` running on `premerge-linux-1` while building `llvm` at step 6 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/26650

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

```
Step 6 (build-unified-tree) failure: build (failure)
...
16.416 [4434/58/81] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineOutliner.cpp.o
16.604 [4433/58/82] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RDFGraph.cpp.o
16.619 [4432/58/83] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetRegisterInfo.cpp.o
16.707 [4431/58/84] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocFast.cpp.o
16.714 [4430/58/85] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/StackSlotColoring.cpp.o
16.720 [4429/58/86] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TailDuplicator.cpp.o
17.045 [4428/58/87] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBlockPlacement.cpp.o
17.232 [4427/58/88] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VirtRegMap.cpp.o
17.530 [4426/58/89] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ResourcePriorityQueue.cpp.o
17.659 [4425/58/90] 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/build/buildbot/premerge-monolithic-linux/build/lib/CodeGen -I/build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/CodeGen -I/build/buildbot/premerge-monolithic-linux/build/include -I/build/buildbot/premerge-monolithic-linux/llvm-project/llvm/include -gmlt -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  -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 /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp
/build/buildbot/premerge-monolithic-linux/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, [...]>'
                            InstIdxForVirtReg, Root.getOperand(0).getReg());
                            ^~~~~~~~~~~~~~~~~
/build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note: passing argument to parameter 'InstrIdxForVirtReg' here
    DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
                                  ^
1 error generated.
17.699 [4425/57/91] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VLIWMachineScheduler.cpp.o
17.970 [4425/56/92] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/PrologEpilogInserter.cpp.o
18.121 [4425/55/93] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ShrinkWrap.cpp.o
18.393 [4425/54/94] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGVLIW.cpp.o
18.427 [4425/53/95] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SplitKit.cpp.o
18.590 [4425/52/96] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGFast.cpp.o
18.611 [4425/51/97] Building CXX object lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
18.632 [4425/50/98] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ScheduleDAGInstrs.cpp.o
18.929 [4425/49/99] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineScheduler.cpp.o
19.665 [4425/48/100] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegisterCoalescer.cpp.o
19.841 [4425/47/101] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/InstrEmitter.cpp.o
19.935 [4425/46/102] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
20.007 [4425/45/103] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
20.260 [4425/44/104] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGSDNodes.cpp.o
20.311 [4425/43/105] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGDumper.cpp.o
20.540 [4425/42/106] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGRRList.cpp.o
20.586 [4425/41/107] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MIRPrinter.cpp.o
20.930 [4425/40/108] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64AdvSIMDScalarPass.cpp.o
21.039 [4425/39/109] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocGreedy.cpp.o
21.047 [4425/38/110] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WindowScheduler.cpp.o
21.413 [4425/37/111] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachinePipeliner.cpp.o
22.034 [4425/36/112] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineVerifier.cpp.o
22.195 [4425/35/113] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FastISel.cpp.o
22.467 [4425/34/114] Building CXX object lib/Target/AArch64/AsmParser/CMakeFiles/LLVMAArch64AsmParser.dir/AArch64AsmParser.cpp.o
22.791 [4425/33/115] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
23.198 [4425/32/116] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64CondBrTuning.cpp.o
23.254 [4425/31/117] Building CXX object lib/CodeGen/MIRParser/CMakeFiles/LLVMMIRParser.dir/MIParser.cpp.o
23.478 [4425/30/118] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64CollectLOH.cpp.o
23.624 [4425/29/119] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/AArch64DeadRegisterDefinitionsPass.cpp.o
23.654 [4425/28/120] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64PostSelectOptimize.cpp.o

```

</details>

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