runtime: remove unnecessary sync from publicationBarrier on s390x

Memory accesses on z are at least as ordered as they are on AMD64.

Change-Id: Ia515430e571ebd07e9314de05c54dc992ab76b95
Reviewed-on: https://go-review.googlesource.com/74010
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Munday <mike.munday@ibm.com>

diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 42b93266074b82cbc0c6bc98ecd6d81ce9801a22..487ed62306cce6e09b3046bc82bbd7eba6ab07ed 100644 (file)
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -915,7 +915,8 @@ TEXT runtime·sigreturn(SB),NOSPLIT,$0-0
        RET
 
 TEXT ·publicationBarrier(SB),NOSPLIT|NOFRAME,$0-0
-       SYNC
+        // Stores are already ordered on s390x, so this is just a
+        // compile barrier.
        RET
 
 TEXT runtime·cmpstring(SB),NOSPLIT|NOFRAME,$0-40