[all-commits] [llvm/llvm-project] 7d21d7: [LAA] Add a test case to show incorrect dependency...

[Alexandros Lamprineas via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7d21d7395ccc8613e5a4144a1b9735e5c719cda3
      https://github.com/llvm/llvm-project/commit/7d21d7395ccc8613e5a4144a1b9735e5c719cda3
  Author: Alexandros Lamprineas <alexandros.lamprineas at arm.com>
  Date:   2023-10-31 (Tue, 31 Oct 2023)

  Changed paths:
    A llvm/test/Analysis/LoopAccessAnalysis/forward-negative-step.ll

  Log Message:
  -----------
  [LAA] Add a test case to show incorrect dependency classification (NFC). (#70473)

Currently the loop access analysis classifies this loop as unsafe to
vectorize because the memory dependencies are
'ForwardButPreventsForwarding'. However, the access pattern is
'write-after-read' with no subsequent read accessing the written memory
locations. I can't see how store-to-load forwarding is applicable here.

void vectorizable_Read_Write(int *A) {
  for (unsigned i = 1022; i >= 0; i--)
    A[i+1] = A[i] + 1;
}