Fix APFloat::getSmallestNormalized so the shift doesn't depend on undefined behavior.  Patch from Ahmed Charles.

llvm-svn: 141818
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index 95df861..f238894 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -3275,7 +3275,7 @@
   Val.exponent = Sem.minExponent;
   Val.zeroSignificand();
   Val.significandParts()[partCountForBits(Sem.precision)-1] |=
-    (((integerPart) 1) << ((Sem.precision % integerPartWidth) - 1));
+    (((integerPart) 1) << ((Sem.precision - 1) % integerPartWidth));
 
   return Val;
 }