[PATCH] D43876: [LoopUnroll] Peel off iterations if it makes conditions true/false.

[Jun Bum Lim via Phabricator via llvm-commits]

junbuml added a comment.

> I am open for suggestions. I think peeling off iterations at the end as Roman suggested might be worthwhile too. And opportunistically peeling off a few iterations, if the distance between start and end are low, but unrolling does not apply.

Peeling off iterations at the end might hit the case I'm trying to optimize. I will be happy to support it.



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Comment at: lib/Transforms/Utils/LoopUnrollPeel.cpp:169
+    CmpInst::Predicate Pred;
+    if (!Condition ||
+        !match(Condition, m_ICmp(Pred, m_Value(LeftVal), m_Value(RightVal))))
----------------
Isn't it okay to remove this nullcheck for  Condition ? 


================
Comment at: lib/Transforms/Utils/LoopUnrollPeel.cpp:192
+      Pred = ICmpInst::getSwappedPredicate(Pred);
+    while (DesiredPeelCount < MaxPeelCount &&
+           SE.isKnownPredicate(Pred, IterVal, RightSCEV)) {
----------------
Do we really need this loop. Isn't it possible to find the count using getMinusSCEV(RightSCEV, LeftSCEV->getStart()) as long as getMinusSCEV(RightSCEV, LeftSCEV->getStart())  is constant ?  


https://reviews.llvm.org/D43876