[PATCH] D97397: [InstCombine] Add a combine for a shuffle of identical bitcasts

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri edited reviewers, added: lebedev.ri; removed: spatel, dmgreen, SjoerdMeijer, fhahn.
lebedev.ri added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp:2297
+  Value *X, *Y;
+  if (match(LHS, m_BitCast(m_Value(X))) && match(RHS, m_BitCast(m_Value(Y))) &&
+      X->getType()->isVectorTy() &&
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One of the original bitcasts needs to be one-use, else we'll increase instruction count.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp:2299
+      X->getType()->isVectorTy() &&
+      cast<FixedVectorType>(X->getType())->getNumElements() == VWidth &&
+      X->getType() == Y->getType()) {
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Can we do anything for the case where we have element count mismatches?


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp:2301
+      X->getType() == Y->getType()) {
+    Value *V = Builder.CreateShuffleVector(X, Y, SVI.getShuffleMask());
+    return new BitCastInst(V, SVI.getType());
----------------



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  https://reviews.llvm.org/D97397/new/

https://reviews.llvm.org/D97397