tree 4c8134f44f15ed2717f998ee5eb629764e02917a
parent 6f9cd79fa2f43b8128be3e4386ee182ad5a843cc
author Philip Reames <preames@rivosinc.com> 1750094409 -0700
committer GitHub <noreply@github.com> 1750094409 -0700
gpgsig -----BEGIN PGP SIGNATURE-----
 
 wsFcBAABCAAQBQJoUFJKCRC1aQ7uu5UhlAAARQkQAI7zxqgSGDAHB93nBzl7sK4K
 R1Y+WYEEUOUUYts6ayH27st0eIrP36UIi9cZtzkoeR/0WabRD2P2xUUbab7adPzm
 Zo/caMtgDEKaBSiDKXxEHja2ZeAFI+1F5UWhhB8NsIO5aDMdcajIUBEwknnh5nu+
 ZKBMYCP0LDuij9yR43iGc2X1OlKp32tJHuD8t/9mvjJWwP1oTteUzCiZj4oXpQ2K
 KLW8XCEQRAoyDx2rI3QUmBHsq5B6QEc5Wz6A4IsTbBAq087ojc5TjIZKN6+d5U6R
 C4jXJUWZffnXd+54yBQLszxy3i1lfdc3GzP6AxYZrqiBbzayba3FzmuuRgKCT2J8
 6d4pcrDTMruLPeRU5K0HB6QYsBQC1usPFbaknlXBSvGJNYrEDviDhzHOBAxRUOS/
 z+UhOPhOEeU2mK4tR16xQMS0bgZU1yMZVjRvmYmQ2bk1y6rOM/n5vfbRkFGI97yC
 mX7DRIUQTSekHMzdWW//tNFmiN7f4U8m94w3mAolLOlV7uMiHzm4t0aCdOeC12+e
 YfyGjncWQW9JI+rodaGtQ9ufrShHASPij+yar9DxcHqZX1ISoG/0/u8QfyVqUUHV
 8k9rSw3OHT+fkvLvtws/asLMGUHA8Kb1NOJW/GgFgju5OJD7aq/smCIwKRRuqky+
 LnaqSRaCy9BOqNZumAkJ
 =HtXD
 -----END PGP SIGNATURE-----
 

[RISCV][TTI] Refine reverse shuffle costing for high LMUL (#144155)

This contains two closely related changes:
1) Explicitly recurse on the i1 case - "3" happens to be the right
   magic constant at m1, but is not otherwise correct, and we're
   better off deferring this to existing logic.
2) Match the lowering for high LMUL shuffles - we've switched to using
   a linear number of m1 vrgather instead of a single big vrgather.
   This results in substantially faster (but also larger) code for
   reverse shuffles larger than m1.  Note that fixed vectors need
   a slide at the end, but scalable ones don't.

This will have the effect of biasing the vectorizer towards larger
(particularly scalable larger) vector factors. This increases VF for the
s112 and s1112 loops from TSVC_2 (in all configurations).

We could refine the high LMUL estimates a bit more, but I think getting
the linear scaling right is probably close enough for the moment.