[MC] Check the upper bound in truncate assertion

The truncateToSize function already has assertion to check the
lower boundary for the number bytes, but it does not check the
upper boundary which could still lead to usage errors.

Differential Revision: http://reviews.llvm.org/D20755

llvm-svn: 271773

lib/MC/MCAsmStreamer.cpp

@@ -314,7 +314,7 @@ void MCAsmStreamer::EmitCommentsAndEOL() {
 }
 
 static inline int64_t truncateToSize(int64_t Value, unsigned Bytes) {
-  assert(Bytes && "Invalid size!");
+  assert(Bytes > 0 && Bytes <= 8 && "Invalid size!");
   return Value & ((uint64_t) (int64_t) -1 >> (64 - Bytes * 8));
 }