Add alternate ConstantRange intersection algorithm.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39851 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/ConstantRange.cpp b/lib/Support/ConstantRange.cpp
index 966de80..4f132e5 100644
--- a/lib/Support/ConstantRange.cpp
+++ b/lib/Support/ConstantRange.cpp
@@ -246,6 +246,87 @@
return *this;
}
+/// maximalIntersectWith - Return the range that results from the intersection
+/// of this range with another range. The resultant range is guaranteed to
+/// include all elements contained in both input ranges, and is also guaranteed
+/// to be the smallest possible set that does so.
+ConstantRange ConstantRange::maximalIntersectWith(const ConstantRange &CR) const {
+ assert(getBitWidth() == CR.getBitWidth() &&
+ "ConstantRange types don't agree!");
+
+ // Handle common cases.
+ if ( isEmptySet() || CR.isFullSet()) return *this;
+ if (CR.isEmptySet() || isFullSet()) return CR;
+
+ if (!isWrappedSet() && CR.isWrappedSet())
+ return CR.maximalIntersectWith(*this);
+
+ if (!isWrappedSet() && !CR.isWrappedSet()) {
+ if (Lower.ult(CR.Lower)) {
+ if (Upper.ule(CR.Lower))
+ return ConstantRange(getBitWidth(), false);
+
+ if (Upper.ult(CR.Upper))
+ return ConstantRange(CR.Lower, Upper);
+
+ return CR;
+ } else {
+ if (Upper.ult(CR.Upper))
+ return *this;
+
+ if (Lower.ult(CR.Upper))
+ return ConstantRange(Lower, CR.Upper);
+
+ return ConstantRange(getBitWidth(), false);
+ }
+ }
+
+ if (isWrappedSet() && !CR.isWrappedSet()) {
+ if (CR.Lower.ult(Upper)) {
+ if (CR.Upper.ult(Upper))
+ return CR;
+
+ if (CR.Upper.ult(Lower))
+ return ConstantRange(CR.Lower, Upper);
+
+ if (getSetSize().ult(CR.getSetSize()))
+ return *this;
+ else
+ return CR;
+ } else if (CR.Lower.ult(Lower)) {
+ if (CR.Upper.ule(Lower))
+ return ConstantRange(getBitWidth(), false);
+
+ return ConstantRange(Lower, CR.Upper);
+ }
+ return CR;
+ }
+
+ if (CR.Upper.ult(Upper)) {
+ if (CR.Lower.ult(Upper)) {
+ if (getSetSize().ult(CR.getSetSize()))
+ return *this;
+ else
+ return CR;
+ }
+
+ if (CR.Lower.ult(Lower))
+ return ConstantRange(Lower, CR.Upper);
+
+ return CR;
+ } else if (CR.Upper.ult(Lower)) {
+ if (CR.Lower.ult(Lower))
+ return *this;
+
+ return ConstantRange(CR.Lower, Upper);
+ }
+ if (getSetSize().ult(CR.getSetSize()))
+ return *this;
+ else
+ return CR;
+}
+
+
/// unionWith - Return the range that results from the union of this range with
/// another range. The resultant range is guaranteed to include the elements of
/// both sets, but may contain more. For example, [3, 9) union [12,15) is