[all-commits] [llvm/llvm-project] 0c2d23: [SystemZTTIImpl] Allow some non-prefetched accesse...

[Jonas Paulsson via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 0c2d23933f06ed048191f84ecde889e9da93609c
      https://github.com/llvm/llvm-project/commit/0c2d23933f06ed048191f84ecde889e9da93609c
  Author: Jonas Paulsson <paulsson at linux.vnet.ibm.com>
  Date:   2020-12-11 (Fri, 11 Dec 2020)

  Changed paths:
    M llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp

  Log Message:
  -----------
  [SystemZTTIImpl] Allow some non-prefetched accesses in getMinPrefetchStride().

The performance improvement on LBM previously achieved with improved software
prefetching (36d4421) have gone lost recently with e00f189. There now is one
memory access in the loop that LoopDataPrefetch cannot handle (while before
there was none) which the heuristic rejects.

This patch adds a small margin by allowing 1 non-prefetched memory access for
every 32 prefetched ones, so that the heuristic doesn't bail in this type of
case.

Review: Ulrich Weigand

Differential Revision: https://reviews.llvm.org/D92985