diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 987b02b..786155a 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -224,11 +224,10 @@
   bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
 
   // FIXME: Warning for overflow.
-  uint64_t Space[4];
+  APSInt Result(DestWidth, !DestSigned);
   bool ignored;
-  (void)Value.convertToInteger(Space, DestWidth, DestSigned,
-                               llvm::APFloat::rmTowardZero, &ignored);
-  return APSInt(llvm::APInt(DestWidth, 4, Space), !DestSigned);
+  (void)Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored);
+  return Result;
 }
 
 static APFloat HandleFloatToFloatCast(QualType DestType, QualType SrcType,
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 3b48201..690a29d 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -3030,18 +3030,16 @@
   if (&Value.getSemantics() == &llvm::APFloat::PPCDoubleDouble)
     return;
 
-  // Try to convert this exactly to an 64-bit integer. FIXME: It would be
-  // nice to support arbitrarily large integers here.
+  // Try to convert this exactly to an integer.
   bool isExact = false;
-  uint64_t IntegerPart;
-  if (Value.convertToInteger(&IntegerPart, 64, /*isSigned=*/true,
+  llvm::APSInt IntegerValue(S.Context.getIntWidth(T),
+                            T->hasUnsignedIntegerRepresentation());
+  if (Value.convertToInteger(IntegerValue,
                              llvm::APFloat::rmTowardZero, &isExact)
       != llvm::APFloat::opOK || !isExact)
     return;
 
-  llvm::APInt IntegerValue(64, IntegerPart, /*isSigned=*/true);
-
-  std::string LiteralValue = IntegerValue.toString(10, /*isSigned=*/true);
+  std::string LiteralValue = IntegerValue.toString(10);
   S.Diag(FL->getExprLoc(), diag::note_fix_integral_float_as_integer)
     << FixItHint::CreateReplacement(FL->getSourceRange(), LiteralValue);
 }