aarch64: Put LR save slot first in more cases

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.

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.

5 files changed, 9 insertions, 9 deletions

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index e8b5dfe..62b1ae0 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 c195050..c54ab2d 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 7e5df84..0d71531 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 ed13487..b41229c 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 96452794..5702656 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\\\]" } } */