Compiler.h: Leave LLVM_BUILTIN_UNREACHABLE undefined if it is unavailable in host...

Users of LLVM_BUILTIN_UNREACHABLE should be responsible in the case when LLVM_BUILTIN_UNREACHABLE is undefined.

Actually, (0, (p)) in LLVM_ASSUME_ALIGNED(p, a) caused thousands of warnings on g++-4.4. It was a motivation in this commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171455 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/Compiler.h b/include/llvm/Support/Compiler.h
index 5ed30a4ef23525d4311cdcb228e14660bbf728a8..b32939eac02a3d8cee11c452d7917820b2010575 100644 (file)
--- a/include/llvm/Support/Compiler.h
+++ b/include/llvm/Support/Compiler.h
@@ -225,8 +225,6 @@
 # define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
 #elif defined(_MSC_VER)
 # define LLVM_BUILTIN_UNREACHABLE __assume(false)
-#else
-# define LLVM_BUILTIN_UNREACHABLE 0
 #endif
 
 /// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
@@ -244,9 +242,11 @@
  || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
 // FIXME: Enable on clang when it supports it.
 # define LLVM_ASSUME_ALIGNED(p, a) __builtin_assume_aligned(p, a)
-#else
+#elif defined(LLVM_BUILTIN_UNREACHABLE)
 # define LLVM_ASSUME_ALIGNED(p, a) \
            (((uintptr_t(p) % (a)) == 0) ? (p) : (LLVM_BUILTIN_UNREACHABLE, (p)))
+#else
+# define LLVM_ASSUME_ALIGNED(p, a) (p)
 #endif
 
 #endif