[libFuzzer] use __attribute__((target("popcnt"))) only on x86_64

llvm-svn: 279601
diff --git a/llvm/lib/Fuzzer/FuzzerValueBitMap.h b/llvm/lib/Fuzzer/FuzzerValueBitMap.h
index e890e1e..2a91733 100644
--- a/llvm/lib/Fuzzer/FuzzerValueBitMap.h
+++ b/llvm/lib/Fuzzer/FuzzerValueBitMap.h
@@ -34,7 +34,7 @@
 
   // Merges 'Other' into 'this', clears 'Other',
   // returns the number of set bits in 'this'.
-  __attribute__((target("popcnt")))
+  ATTRIBUTE_TARGET_POPCNT
   size_t MergeFrom(ValueBitMap &Other) {
     uintptr_t Res = 0;
     for (size_t i = 0; i < kMapSizeInWords; i++) {