vendor/llvm/llvm-release_360-r226102

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/Support/ScaledNumber.cpp b/lib/Support/ScaledNumber.cpp
index 3fe027ba33164..6f6699cfa7c42 100644
--- a/lib/Support/ScaledNumber.cpp
+++ b/lib/Support/ScaledNumber.cpp
@@ -12,7 +12,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/ScaledNumber.h"
-
 #include "llvm/ADT/APFloat.h"
 #include "llvm/Support/Debug.h"
 
@@ -169,6 +168,7 @@ static std::string toStringAPFloat(uint64_t D, int E, unsigned Precision) {
   int Shift = 63 - (NewE - E);
   assert(Shift <= LeadingZeros);
   assert(Shift == LeadingZeros || NewE == ScaledNumbers::MaxScale);
+  assert(Shift >= 0 && Shift < 64 && "undefined behavior");
   D <<= Shift;
   E = NewE;
 
@@ -220,6 +220,9 @@ std::string ScaledNumberBase::toString(uint64_t D, int16_t E, int Width,
   } else if (E > -64) {
     Above0 = D >> -E;
     Below0 = D << (64 + E);
+  } else if (E == -64) {
+    // Special case: shift by 64 bits is undefined behavior.
+    Below0 = D;
   } else if (E > -120) {
     Below0 = D >> (-E - 64);
     Extra = D << (128 + E);