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

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-darwin` running on `doug-worker-3` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/23/builds/8723

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
217.022 [2969/12/3053] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetRegisterInfo.cpp.o
217.039 [2968/12/3054] Copying clang's __stdarg_header_macro.h...
217.045 [2967/12/3055] Copying clang's __stdarg_va_arg.h...
217.072 [2966/12/3056] Copying clang's __stdarg_va_copy.h...
217.089 [2965/12/3057] Copying clang's __stdarg_va_list.h...
217.091 [2964/12/3058] Copying clang's stdatomic.h...
217.126 [2963/12/3059] Copying clang's stdbool.h...
217.157 [2962/12/3060] Copying clang's stdckdint.h...
217.160 [2961/12/3061] Copying clang's stddef.h...
217.173 [2960/12/3062] 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/local/bin/ccache /usr/bin/clang++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/Users/buildbot/buildbot-root/x86_64-darwin/build/lib/CodeGen -I/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/llvm/lib/CodeGen -I/Users/buildbot/buildbot-root/x86_64-darwin/build/include -I/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/llvm/include -isystem /usr/local/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 -O3 -DNDEBUG -std=c++17 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX14.4.sdk  -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 /Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp
/Users/buildbot/buildbot-root/x86_64-darwin/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());
                            ^~~~~~~~~~~~~~~~~
/Users/buildbot/buildbot-root/x86_64-darwin/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note: passing argument to parameter 'InstrIdxForVirtReg' here
    DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
                                  ^
1 error generated.
217.204 [2960/11/3063] Copying clang's __stddef_header_macro.h...
217.209 [2960/10/3064] Copying clang's __stddef_null.h...
217.211 [2960/9/3065] Copying clang's __stddef_max_align_t.h...
218.844 [2960/8/3066] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/UnreachableBlockElim.cpp.o
221.206 [2960/7/3067] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/XRayInstrumentation.cpp.o
221.729 [2960/6/3068] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VirtRegMap.cpp.o
222.109 [2960/5/3069] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/VLIWMachineScheduler.cpp.o
222.890 [2960/4/3070] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
224.571 [2960/3/3071] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WindowScheduler.cpp.o
227.956 [2960/2/3072] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/VarLocBasedImpl.cpp.o
233.076 [2960/1/3073] 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