[all-commits] [llvm/llvm-project] 80c643: [SystemZ][z/OS] Save (and restore) R3 to avoid clo...

[Neumann Hon via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 80c643c46422e2af165aacf5d556604b118598b8
      https://github.com/llvm/llvm-project/commit/80c643c46422e2af165aacf5d556604b118598b8
  Author: Neumann Hon <neumann.hon at ibm.com>
  Date:   2023-05-12 (Fri, 12 May 2023)

  Changed paths:
    M llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
    M llvm/test/CodeGen/SystemZ/zos-prologue-epilog.ll

  Log Message:
  -----------
  [SystemZ][z/OS] Save (and restore) R3 to avoid clobbering parameter when call stack frame extension is invoked

When the stack frame extension routine is used, the contents of r3 is overwritten.
However, if r3 is live in the prologue (ie. one of the function's parameters
resides in r3), it needs to be saved. We save r3 in r0 if r0 is available
(ie. r0 is not used as temporary storage for r4), and in the corresponding
stack slot for the third parameter otherwise.

Differential Revision: https://reviews.llvm.org/D150332

Reviewed By: uweigand