[PATCH] D142542: [InstSimplify] Simplify icmp between Left-Shifted VScale Calls

[Dave Green via Phabricator via llvm-commits]

dmgreen added inline comments.


================
Comment at: llvm/lib/Analysis/InstructionSimplify.cpp:3634
+  ConstantInt *IntLHS, *IntRHS;
+  if (!match(LHS, m_Shl(m_VScale(Q.DL), m_ConstantInt(IntLHS))) ||
+      !match(RHS, m_Shl(m_VScale(Q.DL), m_ConstantInt(IntRHS))) ||
----------------
MattDevereau wrote:
> sdesmalen wrote:
> > Does it matter that this is value is `vscale` ?
> > 
> > I would expect that:
> > * `(X << C1) < (X << C2) == true` for any value `X` for any `C1 < C2`
> > * `(X << C1) <= (X << C2) == true` for any value `X` for any `C1 <= C2`
> > * `(X << C1) > (X << C2) == true` for any value `X` for any `C1 > C2`
> > * ...
> Very true, I think I got a bit too tunnel visioned on the original test case. I will replace the vscale checks with m_Value for LHS and m_Deferred for RHS, and remove any references to vscale in names
Make sure you check the value isn't 0, and it can be good to provide alive proofs.


Repository:
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  https://reviews.llvm.org/D142542/new/

https://reviews.llvm.org/D142542