From c4f0e121faa36342f1d21919e54a05ad841c4f86 Mon Sep 17 00:00:00 2001
From: Richard Sandiford <richard.sandiford@arm.com>
Date: Tue, 12 Sep 2023 16:08:55 +0100
Subject: [PATCH] aarch64: Simplify probe of final frame allocation

Previous patches ensured that the final frame allocation only needs
a probe when the size is strictly greater than 1KiB.  It's therefore
safe to use the normal 1024 probe offset in all cases.

The main motivation for doing this is to simplify the code and
remove the number of special cases.

gcc/
	* config/aarch64/aarch64.cc (aarch64_allocate_and_probe_stack_space):
	Always probe the residual allocation at offset 1024, asserting
	that that is in range.

gcc/testsuite/
	* gcc.target/aarch64/stack-check-prologue-17.c: Expect the probe
	to be at offset 1024 rather than offset 0.
	* gcc.target/aarch64/stack-check-prologue-18.c: Likewise.
	* gcc.target/aarch64/stack-check-prologue-19.c: Likewise.
---
 gcc/config/aarch64/aarch64.cc                        | 12 ++++--------
 .../gcc.target/aarch64/stack-check-prologue-17.c     |  2 +-
 .../gcc.target/aarch64/stack-check-prologue-18.c     |  4 ++--
 .../gcc.target/aarch64/stack-check-prologue-19.c     |  4 ++--
 4 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 16433fb70f4f..8abf3d7a1e2b 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -9523,16 +9523,12 @@ aarch64_allocate_and_probe_stack_space (rtx temp1, rtx temp2,
      are still safe.  */
   if (residual)
     {
-      HOST_WIDE_INT residual_probe_offset = guard_used_by_caller;
+      gcc_assert (guard_used_by_caller + byte_sp_alignment <= size);
+
       /* If we're doing final adjustments, and we've done any full page
 	 allocations then any residual needs to be probed.  */
       if (final_adjustment_p && rounded_size != 0)
 	min_probe_threshold = 0;
-      /* If doing a small final adjustment, we always probe at offset 0.
-	 This is done to avoid issues when the final adjustment is smaller
-	 than the probing offset.  */
-      else if (final_adjustment_p && rounded_size == 0)
-	residual_probe_offset = 0;
 
       aarch64_sub_sp (temp1, temp2, residual, frame_related_p);
       if (residual >= min_probe_threshold)
@@ -9543,8 +9539,8 @@ aarch64_allocate_and_probe_stack_space (rtx temp1, rtx temp2,
 		     HOST_WIDE_INT_PRINT_DEC " bytes, probing will be required."
 		     "\n", residual);
 
-	    emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,
-					     residual_probe_offset));
+	  emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,
+					   guard_used_by_caller));
 	  emit_insn (gen_blockage ());
 	}
     }
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c
index 0d8a25d73a24..f0ec1389771d 100644
--- a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c
@@ -33,7 +33,7 @@ int test1(int z) {
 **	...
 **	str	x30, \[sp\]
 **	sub	sp, sp, #1040
-**	str	xzr, \[sp\]
+**	str	xzr, \[sp, #?1024\]
 **	cbnz	w0, .*
 **	bl	g
 **	...
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c
index 82447d20fff5..6383bec5ebcd 100644
--- a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c
@@ -9,7 +9,7 @@ void g();
 **	...
 **	str	x30, \[sp\]
 **	sub	sp, sp, #4064
-**	str	xzr, \[sp\]
+**	str	xzr, \[sp, #?1024\]
 **	cbnz	w0, .*
 **	bl	g
 **	...
@@ -50,7 +50,7 @@ int test1(int z) {
 **	...
 **	str	x30, \[sp\]
 **	sub	sp, sp, #1040
-**	str	xzr, \[sp\]
+**	str	xzr, \[sp, #?1024\]
 **	cbnz	w0, .*
 **	bl	g
 **	...
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c
index 73ac3e4e4eb0..562039b5e9b8 100644
--- a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c
@@ -9,7 +9,7 @@ void g();
 **	...
 **	str	x30, \[sp\]
 **	sub	sp, sp, #4064
-**	str	xzr, \[sp\]
+**	str	xzr, \[sp, #?1024\]
 **	cbnz	w0, .*
 **	bl	g
 **	...
@@ -50,7 +50,7 @@ int test1(int z) {
 **	...
 **	str	x30, \[sp\]
 **	sub	sp, sp, #1040
-**	str	xzr, \[sp\]
+**	str	xzr, \[sp, #?1024\]
 **	cbnz	w0, .*
 **	bl	g
 **	...
-- 
2.43.5