Mark negative-zero-to-int conversion as Inexact,

since -0.0 can't be represented as an int.
This prevents llvm from reducing -0.0 to a
load-and-convert of int 0.  Fixes
ieee.exp/mzero[2356].c in gcc testsuite.

llvm-svn: 57224

lib/Support/APFloat.cpp

@@ -1784,7 +1784,8 @@ APFloat::convertToSignExtendedInteger(integerPart *parts, unsigned int width,
 
   if(category == fcZero) {
     APInt::tcSet(parts, 0, dstPartsCount);
-    return opOK;
+    // Negative zero can't be represented as an int.
+    return sign ? opInexact : opOK;
   }
 
   src = significandParts();