[PATCH] D45664: [InstCombine] Canonicalize variable mask in masked merge
Roman Lebedev via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 19 09:32:31 PDT 2018
lebedev.ri added inline comments.
================
Comment at: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp:2495-2497
+ if (Instruction *Xor = invertMaskInMaskedMerge(I, Builder))
+ return Xor;
+
----------------
spatel wrote:
> Make sure I haven't missed anything, but it seems easier to match this inline here more simply as:
>
> // Eliminate a 'not' from xor form of masked-merge (aka, bitwise select).
> // The 'not' must be operand 1 of the 'and' (complexity-based op ordering).
> // ((Op1 ^ X) & ~Y) ^ Op1 --> ((Op1 ^ X) & Y) ^ X
> if (match(Op0, m_OneUse(m_And(m_c_Xor(m_Specific(Op1), m_Value(X)),
> m_Not(m_Value(Y)))))) {
> Value *Op00 = cast<BinaryOperator>(Op0)->getOperand(0);
> return BinaryOperator::CreateXor(Builder.CreateAnd(Op00, Y), X);
> }
> // Op0 ^ ((Op0 ^ X) & ~Y) --> ((Op0 ^ X) & Y) ^ X
> if (match(Op1, m_OneUse(m_And(m_c_Xor(m_Specific(Op0), m_Value(X)),
> m_Not(m_Value(Y)))))) {
> Value *Op10 = cast<BinaryOperator>(Op1)->getOperand(0);
> return BinaryOperator::CreateXor(Builder.CreateAnd(Op10, Y), X);
> }
>
I'm sorry, i don't really like this, especially after seeing the DAGCombiner :)
I'm going to work on fixing the commutability problem of `BinaryOp_match` and `m_Specific()`.
(if that fix won't be accepted, will revisit this.)
Repository:
rL LLVM
https://reviews.llvm.org/D45664
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