Fix undefined behavior (left shift by 64 bits) in ScaledNumber::toString().

This bug is reported by UBSan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216116 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/ScaledNumber.cpp b/lib/Support/ScaledNumber.cpp
index 3fe027ba33164f156a3678ee242341e70ec0cb38..fc6d4e7be43a5baaaa3667f7029eec72a3f45b7f 100644 (file)
--- a/lib/Support/ScaledNumber.cpp
+++ b/lib/Support/ScaledNumber.cpp
@@ -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);