make ConstantRange::signExtend() optimal
the case [x, INT_MIN) was not handled optimally
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193694 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/ConstantRange.cpp b/lib/Support/ConstantRange.cpp
index 1085a45..e3b43ed 100644
--- a/lib/Support/ConstantRange.cpp
+++ b/lib/Support/ConstantRange.cpp
@@ -445,6 +445,11 @@
unsigned SrcTySize = getBitWidth();
assert(SrcTySize < DstTySize && "Not a value extension");
+
+ // special case: [X, INT_MIN) -- not really wrapping around
+ if (Upper == APInt::getHighBitsSet(SrcTySize, 1))
+ return ConstantRange(Lower.sext(DstTySize), Upper.zext(DstTySize));
+
if (isFullSet() || isSignWrappedSet()) {
return ConstantRange(APInt::getHighBitsSet(DstTySize,DstTySize-SrcTySize+1),
APInt::getLowBitsSet(DstTySize, SrcTySize-1) + 1);