[gcc r12-9856] aarch64: Avoid a use of callee_offset

[gcc r12-9856] aarch64: Avoid a use of callee_offset

[Richard Sandiford]

https://gcc.gnu.org/g:12a8889de169f892d2e927584c00d20b8b7e456f

commit r12-9856-g12a8889de169f892d2e927584c00d20b8b7e456f
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Tue Sep 12 16:08:49 2023 +0100

    aarch64: Avoid a use of callee_offset
    
    When we emit the frame chain, i.e. when we reach Here in this statement
    of aarch64_expand_prologue:
    
      if (emit_frame_chain)
        {
          // Here
          ...
        }
    
    the stack is in one of two states:
    
    - We've allocated up to the frame chain, but no more.
    
    - We've allocated the whole frame, and the frame chain is within easy
      reach of the new SP.
    
    The offset of the frame chain from the current SP is available
    in aarch64_frame as callee_offset.  It is also available as the
    chain_offset local variable, where the latter is calculated from other
    data.  (However, chain_offset is not always equal to callee_offset when
    !emit_frame_chain, so chain_offset isn't redundant.)
    
    In c600df9a4060da3c6121ff4d0b93f179eafd69d1 I switched to using
    chain_offset for the initialisation of the hard frame pointer:
    
           aarch64_add_offset (Pmode, hard_frame_pointer_rtx,
    -                         stack_pointer_rtx, callee_offset,
    +                         stack_pointer_rtx, chain_offset,
                              tmp1_rtx, tmp0_rtx, frame_pointer_needed);
    
    But the later REG_CFA_ADJUST_CFA handling still used callee_offset.
    
    I think the difference is harmless, but it's more logical for the
    CFA note to be in sync, and it's more convenient for later patches
    if it uses chain_offset.
    
    gcc/
            * config/aarch64/aarch64.cc (aarch64_expand_prologue): Use
            chain_offset rather than callee_offset.

Diff:
---
 gcc/config/aarch64/aarch64.cc | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index ae42ffdedbeb..79253322fd7c 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -9670,7 +9670,6 @@ aarch64_expand_prologue (void)
   poly_int64 initial_adjust = frame.initial_adjust;
   HOST_WIDE_INT callee_adjust = frame.callee_adjust;
   poly_int64 final_adjust = frame.final_adjust;
-  poly_int64 callee_offset = frame.callee_offset;
   poly_int64 sve_callee_adjust = frame.sve_callee_adjust;
   poly_int64 below_hard_fp_saved_regs_size
     = frame.below_hard_fp_saved_regs_size;
@@ -9783,8 +9782,7 @@ aarch64_expand_prologue (void)
 	     implicit.  */
 	  if (!find_reg_note (insn, REG_CFA_ADJUST_CFA, NULL_RTX))
 	    {
-	      rtx src = plus_constant (Pmode, stack_pointer_rtx,
-				       callee_offset);
+	      rtx src = plus_constant (Pmode, stack_pointer_rtx, chain_offset);
 	      add_reg_note (insn, REG_CFA_ADJUST_CFA,
 			    gen_rtx_SET (hard_frame_pointer_rtx, src));
 	    }