Fix left shifts by too large exponents in MCParser

(which happened only on error recovery path).

This bug was reported by UBSan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216915 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index a1b469d6797e89fdcd6c68e96c1e131488afdc99..388d2fc3452e8ce05340453ee3cd84127ca79171 100644 (file)
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -2601,13 +2601,14 @@ bool AsmParser::parseDirectiveFill() {
   if (!isUInt<32>(FillExpr) && FillSize > 4)
     Warning(ExprLoc, "'.fill' directive pattern has been truncated to 32-bits");
 
-  int64_t NonZeroFillSize = FillSize > 4 ? 4 : FillSize;
-  FillExpr &= ~0ULL >> (64 - NonZeroFillSize * 8);
-
-  for (uint64_t i = 0, e = NumValues; i != e; ++i) {
-    getStreamer().EmitIntValue(FillExpr, NonZeroFillSize);
-    if (NonZeroFillSize < FillSize)
-      getStreamer().EmitIntValue(0, FillSize - NonZeroFillSize);
+  if (NumValues > 0) {
+    int64_t NonZeroFillSize = FillSize > 4 ? 4 : FillSize;
+    FillExpr &= ~0ULL >> (64 - NonZeroFillSize * 8);
+    for (uint64_t i = 0, e = NumValues; i != e; ++i) {
+      getStreamer().EmitIntValue(FillExpr, NonZeroFillSize);
+      if (NonZeroFillSize < FillSize)
+        getStreamer().EmitIntValue(0, FillSize - NonZeroFillSize);
+    }
   }
 
   return false;