[PATCH] D33221: [InstSimplify] add folds for constant mask of value shifted by constant
Sanjay Patel via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue May 16 08:45:39 PDT 2017
spatel added inline comments.
================
Comment at: lib/Analysis/InstructionSimplify.cpp:1770
+ if (match(Op0, m_LShr(m_Value(X), m_APInt(ShAmt))) &&
+ Mask->shl(*ShAmt).ashr(*ShAmt).isAllOnesValue())
+ return Op0;
----------------
efriedma wrote:
> `(~*Mask).shl(*ShAmt).isNullValue()`? Not sure that's better.
Looks better to me - we can use the inverted mask for both cases to make things symmetrical.
That also makes it easier to write the Alive tests:
http://rise4fun.com/Alive/lY0
https://reviews.llvm.org/D33221
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