[llvm] [SelectionDAG] Split SDNode::use_iterator into user_iterator and use_iterator. (PR #120531)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-m68k-linux-cross` running on `suse-gary-m68k-cross` while building `llvm` at step 4 "build stage 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/27/builds/3721

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

```
Step 4 (build stage 1) failure: 'ninja' (failure)
...
[89/313] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LoadStoreOpt.cpp.o
[90/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/GISel/M68kRegisterBankInfo.cpp.o
[91/313] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/RegBankSelect.cpp.o
[92/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/GISel/M68kCallLowering.cpp.o
[93/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kExpandPseudo.cpp.o
[94/313] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
[95/313] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/Legalizer.cpp.o
[96/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kAsmPrinter.cpp.o
[97/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kMachineFunction.cpp.o
[98/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kISelLowering.cpp.o
FAILED: lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kISelLowering.cpp.o 
/usr/bin/c++ -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/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/lib/Target/M68k -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/include -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -fno-lifetime-dse -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-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 -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17 -fvisibility=hidden  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kISelLowering.cpp.o -MF lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kISelLowering.cpp.o.d -o lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kISelLowering.cpp.o -c /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp: In function ‘void lowerOverflowArithmetic(llvm::SDValue, llvm::SelectionDAG&, llvm::SDValue&, llvm::SDValue&, unsigned int&)’:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp:1596:25: warning: enumerated mismatch in conditional expression: ‘llvm::ISD::NodeType’ vs ‘llvm::M68kISD::NodeType’ [-Wenum-compare]
 1596 |     BaseOp = NoOverflow ? ISD::MUL : M68kISD::UMUL;
      |              ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp:1602:25: warning: enumerated mismatch in conditional expression: ‘llvm::ISD::NodeType’ vs ‘llvm::M68kISD::NodeType’ [-Wenum-compare]
 1602 |     BaseOp = NoOverflow ? ISD::MUL : M68kISD::SMUL;
      |              ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp: In function ‘bool hasNonFlagsUse(llvm::SDValue)’:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp:1851:20: error: cannot convert ‘llvm::SDUse’ to ‘llvm::SDNode*’ in initialization
 1851 |     SDNode *User = *UI;
      |                    ^~~
      |                    |
      |                    llvm::SDUse
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp:1856:14: error: cannot convert ‘llvm::SDUse’ to ‘llvm::SDNode*’ in assignment
 1856 |       User = *User->use_begin();
      |              ^~~~~~~~~~~~~~~~~~
      |              |
      |              llvm::SDUse
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp: In member function ‘llvm::SDValue llvm::M68kTargetLowering::LowerBRCOND(llvm::SDValue, llvm::SelectionDAG&) const’:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/lib/Target/M68k/M68kISelLowering.cpp:2545:26: error: cannot convert ‘llvm::SDUse’ to ‘llvm::SDNode*’ in initialization
 2545 |           SDNode *User = *Op.getNode()->use_begin();
      |                          ^~~~~~~~~~~~~~~~~~~~~~~~~~
      |                          |
      |                          llvm::SDUse
[99/313] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/Utils.cpp.o
[100/313] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGISel.cpp.o
[101/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kRegisterInfo.cpp.o
[102/313] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugValues/InstrRefBasedImpl.cpp.o
[103/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kMCInstLower.cpp.o
[104/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kInstrInfo.cpp.o
[105/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kFrameLowering.cpp.o
[106/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kISelDAGToDAG.cpp.o
[107/313] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/CodeViewDebug.cpp.o
[108/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/GISel/M68kInstructionSelector.cpp.o
[109/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kSubtarget.cpp.o
[110/313] Building CXX object lib/Target/M68k/CMakeFiles/LLVMM68kCodeGen.dir/M68kTargetObjectFile.cpp.o
[111/313] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86AvoidTrailingCall.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/120531