From 82bbe6513987a7656150110164e25f44fe410796 Mon Sep 17 00:00:00 2001
From: Richard Sandiford <richard.sandiford@arm.com>
Date: Tue, 12 Sep 2023 16:05:05 +0100
Subject: [PATCH 085/157] [Backport][SME] aarch64: Explicitly handle frames
 with no saved registers

Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=c601c918c9ac01ef8315774a642ff924f77c85e5

If a frame has no saved registers, it can be allocated in one go.
There is no need to treat the areas below and above the saved
registers as separate.

And if we allocate the frame in one go, it should be allocated
as the initial_adjust rather than the final_adjust.  This allows the
frame size to grow to guard_size - guard_used_by_caller before a stack
probe is needed.  (A frame with no register saves is necessarily a
leaf frame.)

This is a no-op as thing stand, since a leaf function will have
no outgoing arguments, and so all the frame will be above where
the saved registers normally go.

gcc/
	* config/aarch64/aarch64.cc (aarch64_layout_frame): Explicitly
	allocate the frame in one go if there are no saved registers.
---
 gcc/config/aarch64/aarch64.cc | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index fbd7a079a..c59af6b1c 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -8978,9 +8978,11 @@ aarch64_layout_frame (void)
 
   HOST_WIDE_INT const_size, const_outgoing_args_size, const_fp_offset;
   HOST_WIDE_INT const_saved_regs_size;
-  if (frame.frame_size.is_constant (&const_size)
-      && const_size < max_push_offset
-      && known_eq (frame.hard_fp_offset, const_size))
+  if (known_eq (frame.saved_regs_size, 0))
+    frame.initial_adjust = frame.frame_size;
+  else if (frame.frame_size.is_constant (&const_size)
+	   && const_size < max_push_offset
+	   && known_eq (frame.hard_fp_offset, const_size))
     {
       /* Simple, small frame with no outgoing arguments:
 
-- 
2.33.0