For ppc gcc, implement 64-bit compare_exchange and fetch_add with asm.
While xlc defines __64BIT__, gcc does not. Due to this oversight in
commit 30ee5d17c20dbb282a9952b3048d6ad52d56c371, gcc builds continued
implementing 64-bit atomics by way of intrinsics. Back-patch to v13,
where that commit
For ppc gcc, implement 64-bit compare_exchange and fetch_add with asm.
While xlc defines __64BIT__, gcc does not. Due to this oversight in
commit 30ee5d17c20dbb282a9952b3048d6ad52d56c371, gcc builds continued
implementing 64-bit atomics by way of intrinsics. Back-patch to v13,
where that commit
