[llvm-branch-commits] [llvm] [LoopInterchange] Reject if inner loop IV has outer-variant step (PR #202751)

[Ryotaro Kasuga via llvm-branch-commits]

================
@@ -1251,8 +1251,14 @@ bool 
LoopInterchangeLegality::checkInductionsAndReductions(Loop *OuterLoop) {
     for (PHINode &PHI : CurLoop->getHeader()->phis()) {
       InductionDescriptor ID;
       if (InductionDescriptor::isInductionPHI(&PHI, CurLoop, SE, ID)) {
-        if (CurLoop == InnerLoop)
+        if (CurLoop == InnerLoop) {
----------------
kasuga-fj wrote:

Yes, I believe so. I think the miscompilation we're seeing now is caused by the 
inner loop's IV depending on the outer loop's IV in the very loops we are 
actually attempting to interchange. Deeper nested loops shouldn’t be involved 
in this issue...

https://github.com/llvm/llvm-project/pull/202751
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