[PATCH 05/19] aarch64: Add bytes_below_hard_fp to frame info

[Richard Sandiford <richard.sandiford@arm.com>]

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.
---
 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 49c2fbedd14..58dd8946232 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -8569,6 +8569,7 @@ 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.  */
@@ -10220,8 +10221,7 @@ 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
@@ -10279,7 +10279,7 @@ 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 83939991eb1..75fd3b59b0d 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -785,6 +785,11 @@ 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.  */
-- 
2.25.1