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[mlir][Vector] Add a vblendps-based impl for transpose8x8 (both intrin and inline_asm)
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Authored by nicolasvasilache on Nov 22 2021, 1:16 PM.

Details

Summary

This revision follows up on the conversation titled:

[llvm-dev] Understanding and controlling some of the AVX shuffle emission paths

The revision adds a vblendps-based implementation for transpose8x8 and further distinguishes between and intrinsics and an inline_asm implementation.

This results in roughly 20% fewer cycles as reported by llvm-mca:

After this revision (intrinsic version, resolves to virtually identical assembly as per the llvm-dev discussion, no vblendps instruction is emitted):

Iterations:        100
Instructions:      5900
Total Cycles:      2415
Total uOps:        7300

Dispatch Width:    6
uOps Per Cycle:    3.02
IPC:               2.44
Block RThroughput: 24.0

Cycles with backend pressure increase [ 89.90% ]
Throughput Bottlenecks:
  Resource Pressure       [ 89.65% ]
  - SKXPort1  [ 0.04% ]
  - SKXPort2  [ 12.42% ]
  - SKXPort3  [ 12.42% ]
  - SKXPort5  [ 89.52% ]
  Data Dependencies:      [ 37.06% ]
  - Register Dependencies [ 37.06% ]
  - Memory Dependencies   [ 0.00% ]

After this revision (inline_asm version, vblendps instructions are indeed emitted):

Iterations:        100
Instructions:      6300
Total Cycles:      2015
Total uOps:        7700

Dispatch Width:    6
uOps Per Cycle:    3.82
IPC:               3.13
Block RThroughput: 20.0

Cycles with backend pressure increase [ 83.47% ]
Throughput Bottlenecks:
  Resource Pressure       [ 83.18% ]
  - SKXPort0  [ 14.49% ]
  - SKXPort1  [ 14.54% ]
  - SKXPort2  [ 19.70% ]
  - SKXPort3  [ 19.70% ]
  - SKXPort5  [ 83.03% ]
  - SKXPort6  [ 14.49% ]
  Data Dependencies:      [ 39.75% ]
  - Register Dependencies [ 39.75% ]
  - Memory Dependencies   [ 0.00% ]

An accessible copy of the conversation is available here.

Diff Detail

Event Timeline

nicolasvasilache requested review of this revision.Nov 22 2021, 1:16 PM
Herald added a project: Restricted Project. · View Herald TranscriptNov 22 2021, 1:16 PM

This is a fix of the issue that triggered the revert: https://reviews.llvm.org/rGe0b7bee7cf8ece5ec41c8343b61e1daf651e4f3a

Windows did not like the uint template type so this replaces it with uint8_t.

This revision was not accepted when it landed; it landed in state Needs Review.Nov 22 2021, 11:35 PM
This revision was automatically updated to reflect the committed changes.