[all-commits] [llvm/llvm-project] 5110ff: [AArch64][CostModel] Fix cost for mul <2 x i64>

[sjoerdmeijer via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 5110ff08176f29eefd7638e328d65dfd1c1ad042
      https://github.com/llvm/llvm-project/commit/5110ff08176f29eefd7638e328d65dfd1c1ad042
  Author: Sjoerd Meijer <sjoerd.meijer at arm.com>
  Date:   2020-11-30 (Mon, 30 Nov 2020)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
    M llvm/test/Analysis/CostModel/AArch64/mul.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll
    M llvm/test/Transforms/SLPVectorizer/AArch64/mul.ll

  Log Message:
  -----------
  [AArch64][CostModel] Fix cost for mul <2 x i64>

This was modeled to have a cost of 1, but since we do not have a MUL.2d this is
scalarized into vector inserts/extracts and scalar muls.

Motivating precommitted test is test/Transforms/SLPVectorizer/AArch64/mul.ll,
which we don't want to SLP vectorize.

Test Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll
unfortunately needed changing, but the reason is documented in
LoopVectorize.cpp:6855:

  // The cost of executing VF copies of the scalar instruction. This opcode
  // is unknown. Assume that it is the same as 'mul'.

which I will address next as a follow up of this.

Differential Revision: https://reviews.llvm.org/D92208