Don't allow MCStreamer::EmitIntValue to output 0-byte integers.

It makes no sense and can hide bugs. In particular, it lead
to left shift by 64 bits, which is an undefined behavior,
properly reported by UBSan.

llvm-svn: 216134

2 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index c01f3acc661..aafc5e1850e 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -2612,7 +2612,8 @@ bool AsmParser::parseDirectiveFill() {
 
   for (uint64_t i = 0, e = NumValues; i != e; ++i) {
     getStreamer().EmitIntValue(FillExpr, NonZeroFillSize);
-    getStreamer().EmitIntValue(0, FillSize - NonZeroFillSize);
+    if (NonZeroFillSize < FillSize)
+      getStreamer().EmitIntValue(0, FillSize - NonZeroFillSize);
   }
 
   return false;
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index e7ee9e481bf..914e3372670 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -72,7 +72,7 @@ void MCStreamer::generateCompactUnwindEncodings(MCAsmBackend *MAB) {
 /// EmitIntValue - Special case of EmitValue that avoids the client having to
 /// pass in a MCExpr for constant integers.
 void MCStreamer::EmitIntValue(uint64_t Value, unsigned Size) {
-  assert(Size <= 8 && "Invalid size");
+  assert(1 <= Size && Size <= 8 && "Invalid size");
   assert((isUIntN(8 * Size, Value) || isIntN(8 * Size, Value)) &&
          "Invalid size");
   char buf[8];