[PATCH] D159203: [InstCombine] Fold (A/-B)==(A/B) to (A/B)==0

[Marc Auberer via Phabricator via llvm-commits]

marcauberer marked an inline comment as done.
marcauberer added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:5174
+        match(Op1, m_SDiv(m_Deferred(A), m_Deferred(B))) &&
+        isKnownNonEqual(B, MinVal, DL, &AC, &I, &DT, true)) {
+      return new ICmpInst(Pred, Op1, Constant::getNullValue(A->getType()));
----------------
marcauberer wrote:
> goldstein.w.n wrote:
> > Can you split the `isKnownNonEqual` to a new patch and use either `IsCondKnownTrue` here or probably more direct in this case just use `computeKnownBits`.
> How would I do that with `computeKnownBits`?
> 
> The following code does not seem to work, probably due to the fact that the assumption is not made for value A or B, but rather the icmp ne of A/B with MIN_INT:
> 
> 
> ```
> // Check if A is known to be != INT_MIN
> KnownBits KnownA = computeKnownBits(A, 0, &I);
> if (KnownA.isConstant() && KnownA.getConstant() == MinInt)
>   return new ICmpInst(Pred, Op1, Constant::getNullValue(A->getType()));
> ```
@goldstein.w.n ping? Or is this resolved with extracting the `isKnownNonEqual` part to a new patch? This is done now.


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  https://reviews.llvm.org/D159203/new/

https://reviews.llvm.org/D159203