- if (AI.ule(SE->getUnsignedRange(BA).getUnsignedMin())) {
- APInt BI(BitWidth, BSize);
- const SCEV *AB = SE->getMinusSCEV(AS, BS);
- if (BI.ule(SE->getUnsignedRange(AB).getUnsignedMin()))
- return NoAlias;
- }
+
+ // Test whether the difference is known to be great enough that memory of
+ // the given sizes don't overlap. This assumes that ASizeInt and BSizeInt
+ // are non-zero, which is special-cased above.
+ if (ASizeInt.ule(SE->getUnsignedRange(BA).getUnsignedMin()) &&
+ (-BSizeInt).uge(SE->getUnsignedRange(BA).getUnsignedMax()))
+ return NoAlias;
+
+ // Folding the subtraction while preserving range information can be tricky
+ // (because of INT_MIN, etc.); if the prior test failed, swap AS and BS
+ // and try again to see if things fold better that way.
+
+ // Compute the difference between the two pointers.
+ const SCEV *AB = SE->getMinusSCEV(AS, BS);
+
+ // Test whether the difference is known to be great enough that memory of
+ // the given sizes don't overlap. This assumes that ASizeInt and BSizeInt
+ // are non-zero, which is special-cased above.
+ if (BSizeInt.ule(SE->getUnsignedRange(AB).getUnsignedMin()) &&
+ (-ASizeInt).uge(SE->getUnsignedRange(AB).getUnsignedMax()))
+ return NoAlias;