For ppc gcc, implement 64-bit compare_exchange and fetch_add with asm.

nmisch · nmisch · commit f5c1167b173d · 2020-10-11T21:31:37.000-07:00
While xlc defines __64BIT__, gcc does not. Due to this oversight in commit 30ee5d1, gcc builds continued implementing 64-bit atomics by way of intrinsics. Back-patch to v13, where that commit first appeared. Reviewed by Tom Lane. Discussion: https://postgr.es/m/20201011051043.GA1724101@rfd.leadboat.com
diff --git a/src/include/port/atomics/arch-ppc.h b/src/include/port/atomics/arch-ppc.h
@@ -32,14 +32,14 @@ typedef struct pg_atomic_uint32
 } pg_atomic_uint32;
 
 /* 64bit atomics are only supported in 64bit mode */
-#ifdef __64BIT__
+#if SIZEOF_VOID_P >= 8
 #define PG_HAVE_ATOMIC_U64_SUPPORT
 typedef struct pg_atomic_uint64
 {
 	volatile uint64 value pg_attribute_aligned(8);
 } pg_atomic_uint64;
 
-#endif /* __64BIT__ */
+#endif
 
 /*
  * This mimics gcc __atomic_compare_exchange_n(..., __ATOMIC_SEQ_CST), but
