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[SLP] sort candidates to increase chance of optimal compare reduction

Authored by spatel on Sep 17 2020, 5:39 AM.

Description

[SLP] sort candidates to increase chance of optimal compare reduction

This is one (small) part of improving PR41312:
https://llvm.org/PR41312

As shown there and in the smaller tests here, if we have some member of the
reduction values that does not match the others, we want to push it to the
end (bring the matching members forward and together).

In the regression tests, we have 5 candidates for the 4 slots of the reduction.
If the one "wrong" compare is grouped with the others, it prevents forming the
ideal v4i1 compare reduction.

Differential Revision: https://reviews.llvm.org/D87772

Details

Committed
spatelSep 17 2020, 5:49 AM
Differential Revision
D87772: [SLP] sort candidates to increase chance of optimal compare reduction
Parents
rG788c7d2ec11d: [clang][docs] Fix documentation of -O
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