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.

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index e8b5dfe4d5844648c1e8953df515bfed21a6e320..62b1ae0652f4e987806fc1fc6781e25d5d2421b6 100644 (file)
--- 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 c19505082fa1f77e4f039fb3a16027b8003809dc..c54ab2d0ccb486631b57cc19668e2138d51b03e5 100644 (file)
--- 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 7e5df84cf5f92a20a40f1558ab59de663a534ff6..0d715314cb83bde370d67d7cbceb446ac3af5ffd 100644 (file)
--- 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 ed13487a094ad14e5177acc57e4025c45cc80be9..b41229c42f45e163bb31c39eb29b98a180173799 100644 (file)
--- 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 96452794956f9ab34ff2b78cec0a78d5ef255eb3..5702656a5da7135ac218cd91cccfe404d45b5ca0 100644 (file)
--- 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\\\]" } } */