aarch64: Fix up __aarch64_cas16_acq_rel fallback

As mentioned in the PR, the fallback path when LSE is unavailable writes
incorrect registers to the memory if the previous content compares equal
to x0, x1 - it writes copy of x0, x1 from the start of function, but it
should write x2, x3.

2020-08-03  Jakub Jelinek  <jakub@redhat.com>

	PR target/96402
	* config/aarch64/lse.S (__aarch64_cas16_acq_rel): Use x2, x3 instead
	of x(tmp0), x(tmp1) in STXP arguments.

	* gcc.target/aarch64/pr96402.c: New test.

diff --git a/gcc/testsuite/gcc.target/aarch64/pr96402.c b/gcc/testsuite/gcc.target/aarch64/pr96402.c
new file mode 100644 (file)
index 0000000..fa2dddf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/pr96402.c
@@ -0,0 +1,16 @@
+/* PR target/96402 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-moutline-atomics" } */
+
+int
+main ()
+{
+  __int128 a = 0;
+  __sync_val_compare_and_swap (&a, (__int128) 0, (__int128) 1);
+  if (a != 1)
+    __builtin_abort ();
+  __sync_val_compare_and_swap (&a, (__int128) 1, (((__int128) 0xdeadbeeffeedbac1ULL) << 64) | 0xabadcafe00c0ffeeULL);
+  if (a != ((((__int128) 0xdeadbeeffeedbac1ULL) << 64) | 0xabadcafe00c0ffeeULL))
+    __builtin_abort ();
+  return 0;
+}

diff --git a/libgcc/config/aarch64/lse.S b/libgcc/config/aarch64/lse.S
index aa3e3dc..7496b8b 100644 (file)
--- a/libgcc/config/aarch64/lse.S
+++ b/libgcc/config/aarch64/lse.S
@@ -203,7 +203,7 @@ STARTFN     NAME(cas)
        cmp             x0, x(tmp0)
        ccmp            x1, x(tmp1), #0, eq
        bne             1f
-       STXP            w(tmp2), x(tmp0), x(tmp1), [x4]
+       STXP            w(tmp2), x2, x3, [x4]
        cbnz            w(tmp2), 0b
 1:     ret