[all-commits] [llvm/llvm-project] e7bf2e: [LV] Move code to place induction increment to VPl...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e7bf2ea93472bfdab8c5a31b81f94727f1def07b
      https://github.com/llvm/llvm-project/commit/e7bf2ea93472bfdab8c5a31b81f94727f1def07b
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2022-03-28 (Mon, 28 Mar 2022)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/lib/Transforms/Vectorize/VPlan.cpp

  Log Message:
  -----------
  [LV] Move code to place induction increment to VPlan post-processing.

This patch moves the code to set the correct incoming block for the
backedge value to VPlan::execute.

When generating the phi node, the backedge value is temporarily added
using the pre-header as incoming block. The invalid phi node will be
fixed up during VPlan::execute after main VPlan code generation.
At the same time, the backedge value is also moved to the latch.

This change removes the requirement to create the latch block up-front
for VPWidenIntOrFpInductionRecipe::execute, which in turn will enable
modeling the pre-header in VPlan.

As an alternative, the increment could be modeled as separate recipe,
but that would require more work and a bit of redundant code, as we need
to create the step-vector during VPWidenIntOrFpInductionRecipe::execute
anyways, to create the values for different parts.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D121617