[PATCH] D51696: [SelectionDAG] enhance vector demanded elements to look at a vector select condition operand

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: craig.topper, RKSimon, efriedma.
Herald added a subscriber: mcrosier.

This is the DAG equivalent of https://reviews.llvm.org/D51433. 
If we know we're not using all vector lanes, use that knowledge to potentially simplify a vselect condition.

The reduction/horizontal tests show that we are eliminating AVX1 operations on the upper half of 256-bit vectors because we don't need those anyway (double-check to make sure I'm reading those diffs correctly).
I'm not sure what the pr34592 test is showing. That's run with -O0; is SimplifyDemandedVectorElts supposed to be running there?

The removal of the temporary DemandedLHS/DemandedRHS variables is NFC, so we could make that a pre-commit IIUC.


https://reviews.llvm.org/D51696

Files:
  lib/CodeGen/SelectionDAG/TargetLowering.cpp
  test/CodeGen/X86/horizontal-reduce-smax.ll
  test/CodeGen/X86/horizontal-reduce-smin.ll
  test/CodeGen/X86/horizontal-reduce-umax.ll
  test/CodeGen/X86/horizontal-reduce-umin.ll
  test/CodeGen/X86/pr34592.ll
  test/CodeGen/X86/vector-reduce-smax.ll
  test/CodeGen/X86/vector-reduce-smin.ll
  test/CodeGen/X86/vector-reduce-umax.ll
  test/CodeGen/X86/vector-reduce-umin.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D51696.164083.patch
Type: text/x-patch
Size: 22600 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180905/c30daf43/attachment.bin>