Index: llvm/lib/Support/APFloat.cpp
===================================================================
--- llvm/lib/Support/APFloat.cpp
+++ llvm/lib/Support/APFloat.cpp
@@ -3900,8 +3900,7 @@
   zeroSignificand();
   sign = Negative;
   exponent = semantics->minExponent;
-  significandParts()[partCountForBits(semantics->precision) - 1] |=
-      (((integerPart)1) << ((semantics->precision - 1) % integerPartWidth));
+  APInt::tcSetBit(significandParts(), semantics->precision - 1);
 }
 
 IEEEFloat::IEEEFloat(const fltSemantics &Sem, const APInt &API) {