[PATCH] D127398: [InstCombine] add vector support for (A >> C) == (B >> C) --> (A^B) u< (1 << C)

[Sanjay Patel via Phabricator via llvm-commits]

spatel accepted this revision.
spatel added a comment.
This revision is now accepted and ready to land.

LGTM - see inline for some possible minor improvements.



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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:4608
 
   // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
   // For lshr and ashr pairs.
----------------
"C" in the result is not the same as "C" in the source - update this comment to make the transform clearer?


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:4629
   // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
   if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
       match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
----------------
Do you plan to change this one too? It will be easier to read the code and see the early return if we make a smaller helper function to handle the related patterns.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:4646
   if (Op0->hasOneUse() &&
       match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
       match(Op1, m_ConstantInt(Cst1)) &&
----------------
Another transform that can be updated...


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127398/new/

https://reviews.llvm.org/D127398