[PATCH] D100495: [SLP] Add detection of shuffled/perfect matching of tree entries.

[Peter Hawkins via Phabricator via llvm-commits]

phawkins added a comment.

In D100495#2713228 <https://reviews.llvm.org/D100495#2713228>, @ABataev wrote:

> In D100495#2711644 <https://reviews.llvm.org/D100495#2711644>, @bkramer wrote:
>
>> Seeing a miscompile after this has landed. Trying to reduce a test case, but no luck so far.
>
> Any updates about a reproducer?

Here's the smallest reproducer we have so far.

Grab:

- driver.cc: https://gist.github.com/hawkinsp/de3ee1adc72d9e4618e00cde5139a5c3
- buffer-assignment.txt: https://gist.github.com/hawkinsp/01719b73adb20cccb8d06a57267d42a3
- module.ll: https://gist.github.com/hawkinsp/cbe6e3d508f6bf8172d29bd0c6f986a0

and run (on a machine that supports AVX 512):

  llvm-project/build/bin/clang  module.ll  driver.cc -o repro -march=skylake-avx512 -O3 -lstdc++ -lm
  ./repro buffer-assignment.txt

Before this PR (at the preceding commit) this repro produces:

  Output:
  0.502001, -0.462127, 0.459155, 0.10126, -0.0533019, -0.557239

After this PR, this repro produces:

  Output:
  0.519662, -0.450291, 0.492509, 0.0910437, -0.0563238, -0.522649

We expect the error in this procedure to be accurate to something more like 1e-10, so this is a significant difference.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100495/new/

https://reviews.llvm.org/D100495