On Sun, 2023-11-19 at 17:47 -0700, Jeff Law wrote: > This is work originally started by Joern @ Embecosm. > > There's been a long standing sense that we're generating too many > sign/zero extensions on the RISC-V port. REE is useful, but it's really > focused on a relatively narrow part of the extension problem. > > What Joern's patch does is introduce a new pass which tracks liveness of > chunks of pseudo regs. Specifically it tracks bits 0..7, 8..15, 16..31 > and 32..63. > > If it encounters a sign/zero extend that sets bits that are never read, > then it replaces the sign/zero extension with a narrowing subreg. The > narrowing subreg usually gets eliminated by subsequent passes (it's just > a copy after all). >
Have you tried it on SH, too? (and if so any numbers?) It sounds like this one would be great to remove some of the sign/zero extension removal hackery that I've accumulated in the SH backend. Cheers, Oleg
