On Thu, May 25, 2023 at 1:10 PM Alexandre Oliva <ol...@adacore.com> wrote: > > On May 25, 2023, Richard Biener <richard.guent...@gmail.com> wrote: > > > I mean we could do what RTL expansion would do later and do > > by-pieces, thus emit multiple loads/stores but not n loads and then > > n stores but interleaved. > > That wouldn't help e.g. gcc.dg/memcpy-6.c's fold_move_8, because > MOVE_MAX and MOVE_MAX_PIECES currently limits inline expansion to 4 > bytes on x86 without SSE, both in gimple and RTL, and interleaved loads > and stores wouldn't help with memmove. We can't fix that by changing > code that uses MOVE_MAX and/or MOVE_MAX_PIECES, when these limits are > set too low. > > I'm also concerned that doing more such expansion in gimple folding > would be reversed in later gimple passes. That's good in that it would > enable efficient rtl movmem/cpymem instruction selection, but it's not > clear to me that there would generally be benefits to such early > open-coding in gimple.
Btw, there was a short period where the MOVE_MAX limit was restricted but that had fallout and we've reverted since then. Richard. > -- > Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ > Free Software Activist GNU Toolchain Engineer > Disinformation flourishes because many people care deeply about injustice > but very few check the facts. Ask me about <https://stallmansupport.org>
