[all-commits] [llvm/llvm-project] 495d3e: [MachineSink][RISCV] Only call isConstantPhysReg o...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 495d3ea989d4e97ce77ee73d6b35b171a7346019
      https://github.com/llvm/llvm-project/commit/495d3ea989d4e97ce77ee73d6b35b171a7346019
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2024-07-17 (Wed, 17 Jul 2024)

  Changed paths:
    M llvm/lib/CodeGen/MachineSink.cpp
    A llvm/test/CodeGen/RISCV/sink-and-fold-crash.mir

  Log Message:
  -----------
  [MachineSink][RISCV] Only call isConstantPhysReg or isIgnorableUse for uses. (#99363)

The included test case contains X0 as a def register. X0 is considered a
constant register when it is a use. When its a def, it means to throw
away the result value.

If we treat it as a constant register here, we will execute the continue
and not assign `DefReg` to any register. This will cause a crash when
trying to get the register class for `DefReg` after the loop.

By only checking isConstantPhysReg for uses, we will reach the `return
false` a little further down and stop processing this instruction.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications