[gcc r12-9859] aarch64: Add bytes_below_hard_fp to frame info

[gcc r12-9859] aarch64: Add bytes_below_hard_fp to frame info

[Richard Sandiford]

https://gcc.gnu.org/g:34081079ea4de0c98331843f574b5f6f94d7b234

commit r12-9859-g34081079ea4de0c98331843f574b5f6f94d7b234
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Tue Sep 12 16:08:50 2023 +0100

    aarch64: Add bytes_below_hard_fp to frame info
    
    Following on from the previous bytes_below_saved_regs patch, this one
    records the number of bytes that are below the hard frame pointer.
    This eventually replaces below_hard_fp_saved_regs_size.
    
    If a frame pointer is not needed, the epilogue adds final_adjust
    to the stack pointer before restoring registers:
    
         aarch64_add_sp (tmp1_rtx, tmp0_rtx, final_adjust, true);
    
    Therefore, if the epilogue needs to restore the stack pointer from
    the hard frame pointer, the directly corresponding offset is:
    
         -bytes_below_hard_fp + final_adjust
    
    i.e. go from the hard frame pointer to the bottom of the frame,
    then add the same amount as if we were using the stack pointer
    from the outset.
    
    gcc/
            * config/aarch64/aarch64.h (aarch64_frame::bytes_below_hard_fp): New
            field.
            * config/aarch64/aarch64.cc (aarch64_layout_frame): Initialize it.
            (aarch64_expand_epilogue): Use it instead of
            below_hard_fp_saved_regs_size.

Diff:
---
 gcc/config/aarch64/aarch64.cc | 6 +++---
 gcc/config/aarch64/aarch64.h  | 5 +++++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 94e1b6865849..c7d84245fbfc 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -8269,6 +8269,7 @@ aarch64_layout_frame (void)
      of the callee save area.  */
   bool saves_below_hard_fp_p = maybe_ne (offset, 0);
   frame.below_hard_fp_saved_regs_size = offset;
+  frame.bytes_below_hard_fp = offset + frame.bytes_below_saved_regs;
   if (frame.emit_frame_chain)
     {
       /* FP and LR are placed in the linkage record.  */
@@ -9856,8 +9857,7 @@ aarch64_expand_epilogue (bool for_sibcall)
   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;
+  poly_int64 bytes_below_hard_fp = frame.bytes_below_hard_fp;
   unsigned reg1 = frame.wb_pop_candidate1;
   unsigned reg2 = frame.wb_pop_candidate2;
   unsigned int last_gpr = (frame.is_scs_enabled
@@ -9915,7 +9915,7 @@ aarch64_expand_epilogue (bool for_sibcall)
        is restored on the instruction doing the writeback.  */
     aarch64_add_offset (Pmode, stack_pointer_rtx,
 			hard_frame_pointer_rtx,
-			-callee_offset - below_hard_fp_saved_regs_size,
+			-bytes_below_hard_fp + final_adjust,
 			tmp1_rtx, tmp0_rtx, callee_adjust == 0);
   else
      /* The case where we need to re-use the register here is very rare, so
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 1e105e12db8d..de68ff7202fc 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -880,6 +880,11 @@ struct GTY (()) aarch64_frame
      are saved below the hard frame pointer.  */
   poly_int64 below_hard_fp_saved_regs_size;
 
+  /* The number of bytes between the bottom of the static frame (the bottom
+     of the outgoing arguments) and the hard frame pointer.  This value is
+     always a multiple of STACK_BOUNDARY.  */
+  poly_int64 bytes_below_hard_fp;
+
   /* Offset from the base of the frame (incomming SP) to the
      top of the locals area.  This value is always a multiple of
      STACK_BOUNDARY.  */