diff mbox series

[2/2] aarch64: Put LR save slot first in more cases

Message ID mpt1qds3lwq.fsf@arm.com
State New
Headers show
Series [1/2] aarch64: Use vecs to store register save order | expand

Commit Message

Richard Sandiford Oct. 17, 2023, 10:48 p.m. UTC 
Now that the prologue and epilogue code iterates over saved
registers in offset order, we can put the LR save slot first
without compromising LDP/STP formation.

This isn't worthwhile when shadow call stacks are enabled, since the
first two registers are also push/pop candidates, and LR cannot be
popped when shadow call stacks are enabled.  (LR is instead loaded
first and compared against the shadow stack's value.)

But otherwise, it seems better to put the LR save slot first,
to reduce unnecessary variation with the layout for stack clash
protection.

Tested on aarch64-linux-gnu & pushed.

Richard


gcc/
	* config/aarch64/aarch64.cc (aarch64_layout_frame): Don't make
	the position of the LR save slot dependent on stack clash
	protection unless shadow call stacks are enabled.

gcc/testsuite/
	* gcc.target/aarch64/test_frame_2.c: Expect x30 to come before x19.
	* gcc.target/aarch64/test_frame_4.c: Likewise.
	* gcc.target/aarch64/test_frame_7.c: Likewise.
	* gcc.target/aarch64/test_frame_10.c: Likewise.
---
 gcc/config/aarch64/aarch64.cc                    | 2 +-
 gcc/testsuite/gcc.target/aarch64/test_frame_10.c | 4 ++--
 gcc/testsuite/gcc.target/aarch64/test_frame_2.c  | 4 ++--
 gcc/testsuite/gcc.target/aarch64/test_frame_4.c  | 4 ++--
 gcc/testsuite/gcc.target/aarch64/test_frame_7.c  | 4 ++--
 5 files changed, 9 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index e8b5dfe4d58..62b1ae0652f 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -8694,7 +8694,7 @@  aarch64_layout_frame (void)
       allocate_gpr_slot (R29_REGNUM);
       allocate_gpr_slot (R30_REGNUM);
     }
-  else if (flag_stack_clash_protection
+  else if ((flag_stack_clash_protection || !frame.is_scs_enabled)
 	   && known_eq (frame.reg_offset[R30_REGNUM], SLOT_REQUIRED))
     /* Put the LR save slot first, since it makes a good choice of probe
        for stack clash purposes.  The idea is that the link register usually
diff --git a/gcc/testsuite/gcc.target/aarch64/test_frame_10.c b/gcc/testsuite/gcc.target/aarch64/test_frame_10.c
index c19505082fa..c54ab2d0ccb 100644
--- a/gcc/testsuite/gcc.target/aarch64/test_frame_10.c
+++ b/gcc/testsuite/gcc.target/aarch64/test_frame_10.c
@@ -14,6 +14,6 @@ 
 t_frame_pattern_outgoing (test10, 480, "x19", 24, a[8], a[9], a[10])
 t_frame_run (test10)
 
-/* { dg-final { scan-assembler-times "stp\tx19, x30, \\\[sp, \[0-9\]+\\\]" 1 } } */
-/* { dg-final { scan-assembler "ldp\tx19, x30, \\\[sp, \[0-9\]+\\\]" } } */
+/* { dg-final { scan-assembler-times "stp\tx30, x19, \\\[sp, \[0-9\]+\\\]" 1 } } */
+/* { dg-final { scan-assembler "ldp\tx30, x19, \\\[sp, \[0-9\]+\\\]" } } */
 
diff --git a/gcc/testsuite/gcc.target/aarch64/test_frame_2.c b/gcc/testsuite/gcc.target/aarch64/test_frame_2.c
index 7e5df84cf5f..0d715314cb8 100644
--- a/gcc/testsuite/gcc.target/aarch64/test_frame_2.c
+++ b/gcc/testsuite/gcc.target/aarch64/test_frame_2.c
@@ -14,6 +14,6 @@  t_frame_pattern (test2, 200, "x19")
 t_frame_run (test2)
 
 
-/* { dg-final { scan-assembler-times "stp\tx19, x30, \\\[sp, -\[0-9\]+\\\]!" 1 } } */
-/* { dg-final { scan-assembler "ldp\tx19, x30, \\\[sp\\\], \[0-9\]+" } } */
+/* { dg-final { scan-assembler-times "stp\tx30, x19, \\\[sp, -\[0-9\]+\\\]!" 1 } } */
+/* { dg-final { scan-assembler "ldp\tx30, x19, \\\[sp\\\], \[0-9\]+" } } */
 
diff --git a/gcc/testsuite/gcc.target/aarch64/test_frame_4.c b/gcc/testsuite/gcc.target/aarch64/test_frame_4.c
index ed13487a094..b41229c42f4 100644
--- a/gcc/testsuite/gcc.target/aarch64/test_frame_4.c
+++ b/gcc/testsuite/gcc.target/aarch64/test_frame_4.c
@@ -13,6 +13,6 @@ 
 t_frame_pattern (test4, 400, "x19")
 t_frame_run (test4)
 
-/* { dg-final { scan-assembler-times "stp\tx19, x30, \\\[sp, -\[0-9\]+\\\]!" 1 } } */
-/* { dg-final { scan-assembler "ldp\tx19, x30, \\\[sp\\\], \[0-9\]+" } } */
+/* { dg-final { scan-assembler-times "stp\tx30, x19, \\\[sp, -\[0-9\]+\\\]!" 1 } } */
+/* { dg-final { scan-assembler "ldp\tx30, x19, \\\[sp\\\], \[0-9\]+" } } */
 
diff --git a/gcc/testsuite/gcc.target/aarch64/test_frame_7.c b/gcc/testsuite/gcc.target/aarch64/test_frame_7.c
index 96452794956..5702656a5da 100644
--- a/gcc/testsuite/gcc.target/aarch64/test_frame_7.c
+++ b/gcc/testsuite/gcc.target/aarch64/test_frame_7.c
@@ -13,6 +13,6 @@ 
 t_frame_pattern (test7, 700, "x19")
 t_frame_run (test7)
 
-/* { dg-final { scan-assembler-times "stp\tx19, x30, \\\[sp]" 1 } } */
-/* { dg-final { scan-assembler "ldp\tx19, x30, \\\[sp\\\]" } } */
+/* { dg-final { scan-assembler-times "stp\tx30, x19, \\\[sp]" 1 } } */
+/* { dg-final { scan-assembler "ldp\tx30, x19, \\\[sp\\\]" } } */