[PATCH] D29000: [SelectionDAG] Teach getNode to simplify a couple easy cases of EXTRACT_SUBVECTOR
Craig Topper via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sun Jan 22 19:26:08 PST 2017
craig.topper created this revision.
This teaches getNode to simplify extracting from Undef. This is similar to what is done for EXTRACT_VECTOR_ELT. It also adds support for extracting from CONCAT_VECTOR when we can reused one of the inputs to the concat. These seem like simple non-target specific optimizations.
For X86 we currently handle undef in extractSubvector, but not all EXTRACT_SUBVECTOR creations go through there.
Ultimately, my motivation here is to simplify extractSubvector and remove custom lowering for EXTRACT_SUBVECTOR since we don't do anything but handle undef and BUILD_VECTOR optimizations, but those should be DAG combines.
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