[PATCH] D148249: [AArch64] Peep SELECT_CC patterns that match smin(a,0) and smax(a,0).

Cameron McInally via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Thu Apr 13 09:42:49 PDT 2023

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GitHub Issue #61767

With a previous patch to canonicalize SPF to min/max intrinsics (a266af721153 <https://reviews.llvm.org/rGa266af721153fab6452094207b09ed265ab0be7b>), we saw a 6% performance regression from our out-of-tree compiler on 372.smithwa.

This patch attempts to recover from the SPF canonicalization by peeping smin(a,0) and smax(a,0) SELECT_CC patterns during AArch64ISelLowering. We'll match the following patterns:

(SELECT_CC setgt, lhs, 0, lhs, 0) -> (BIC lhs, (SRA lhs, typesize-1))
(SELECT_CC setlt, lhs, 0, lhs, 0) -> (AND lhs, (SRA lhs, typesize-1))

Notice that there's some noise in the existing test cases. They haven't been run through update_llc_test_checks.py since the assembly comments for constants have been added. I will update those tests pre-commit if that will help.

  rG LLVM Github Monorepo



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