[MC] Return early when .fill size is negative

Rather than invoking emitFill with negative size, which may trigger
an undefined behavior, return immediately after emitting the warning.

Differential Revision: http://reviews.llvm.org/D20768

llvm-svn: 271107

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index dcc02a9ab8c..5262558df1a 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -2801,7 +2801,7 @@ bool AsmParser::parseDirectiveFill() {
 
   if (FillSize < 0) {
     Warning(SizeLoc, "'.fill' directive with negative size has no effect");
-    NumValues = MCConstantExpr::create(0, getStreamer().getContext());
+    return false;
   }
   if (FillSize > 8) {
     Warning(SizeLoc, "'.fill' directive with size greater than 8 has been truncated to 8");