[libFuzzer] Check for target(popcnt) capability before usage

Older compilers (e.g. LLVM 3.4) do not support the attribute target("popcnt").
In order to support those, this diff check the attribute support using the preprocessor.

Patch by George Karpenkov.

Differential Revision: https://reviews.llvm.org/D32311

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300999 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Fuzzer/FuzzerDefs.h b/lib/Fuzzer/FuzzerDefs.h
index bd18275..939b92f 100644 (file)
--- a/lib/Fuzzer/FuzzerDefs.h
+++ b/lib/Fuzzer/FuzzerDefs.h
@@ -36,12 +36,20 @@
 #error "Support for your platform has not been implemented"
 #endif
 
+#ifndef __has_attribute
+#  define __has_attribute(x) 0
+#endif
+
 #define LIBFUZZER_POSIX LIBFUZZER_APPLE || LIBFUZZER_LINUX
 
 #ifdef __x86_64
-#define ATTRIBUTE_TARGET_POPCNT __attribute__((target("popcnt")))
+#  if __has_attribute(target)
+#    define ATTRIBUTE_TARGET_POPCNT __attribute__((target("popcnt")))
+#  else
+#    define ATTRIBUTE_TARGET_POPCNT
+#  endif
 #else
-#define ATTRIBUTE_TARGET_POPCNT
+#  define ATTRIBUTE_TARGET_POPCNT
 #endif