LAA: add missed swap when inverting src, sink

[artagnon]

When inverting source and sink on a negative induction step, the types of the source and sink should also be swapped. This fixes a bug in the code that follows, that computes properties based on these types. With 234cc40 ([LAA] Limit no-overlap check to at least one loop-invariant accesses.), that code is guarded by a loop-invariant condition: however, the commit did not add any new tests exercising the guarded code, and hence the bugfix in this patch requires additional tests to exercise that guarded codepath.

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Ramkumar Ramachandra (artagnon)

Changes

We miss swapping the types of the source and sink when the source and sink are inverted, leaving a footgun behind. Fix this.

---

Full diff: https://github.com/llvm/llvm-project/pull/122254.diff

1 Files Affected:

• (modified) llvm/lib/Analysis/LoopAccessAnalysis.cpp (+1)

diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 2c75d5625cb66d..de0f81c0b6a4bf 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1921,6 +1921,7 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
   if (StrideAPtr && *StrideAPtr < 0) {
     std::swap(Src, Sink);
     std::swap(AInst, BInst);
+    std::swap(ATy, BTy);
     std::swap(StrideAPtr, StrideBPtr);
   }
 

[david-arm]

LGTM! Good spot. :)