[all-commits] [llvm/llvm-project] 139215: [IVDescriptor] Find original 'Previous' for first-...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 139215af8e33079a51c95d17a11c42603961d901
      https://github.com/llvm/llvm-project/commit/139215af8e33079a51c95d17a11c42603961d901
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2022-03-03 (Thu, 03 Mar 2022)

  Changed paths:
    M llvm/lib/Analysis/IVDescriptors.cpp
    M llvm/test/Transforms/LoopVectorize/first-order-recurrence-complex.ll

  Log Message:
  -----------
  [IVDescriptor] Find original 'Previous' for first-order recurrences.

This patch extends first-order recurrence handling to support cases
where we already sunk an instruction for a different recurrence, but
LastPrev comes before Previous.

To handle those cases correctly, we need to find the earliest entry for
the sink-after chain, because this is references the Previous from the
original recurrence. This is needed to ensure we use the correct
instruction as sink point.

Depends on D118558.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D118642