[all-commits] [llvm/llvm-project] 84efad: [RISCV][MRI] Account for fixed registers when dete...

[Michael Maitland via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 84efad0b471543003c0724c85f158f66fccfdc0f
      https://github.com/llvm/llvm-project/commit/84efad0b471543003c0724c85f158f66fccfdc0f
  Author: Michael Maitland <michaeltmaitland at gmail.com>
  Date:   2024-12-06 (Fri, 06 Dec 2024)

  Changed paths:
    M llvm/include/llvm/CodeGen/TargetSubtargetInfo.h
    M llvm/lib/CodeGen/MachineRegisterInfo.cpp
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
    M llvm/lib/Target/RISCV/RISCVSubtarget.h
    A llvm/test/CodeGen/RISCV/fixed-csr.ll

  Log Message:
  -----------
  [RISCV][MRI] Account for fixed registers when determining callee saved regs (#115756)

This fixes
https://discourse.llvm.org/t/fixed-register-being-spill-and-restored-in-clang/83058.

We need to do it in `MachineRegisterInfo::getCalleeSavedRegs` instead of
`RISCVRegisterInfo::getCalleeSavedRegs` since the MF argument of
`TargetRegisterInfo:::getCalleeSavedRegs` is `const`, so we can't call
`MF->getRegInfo().disableCalleeSavedRegister` there.

So to put it in `MachineRegisterInfo::getCalleeSavedRegs`, we move
`isRegisterReservedByUser` into `TargetSubtargetInfo`.



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