On 3/5/23 12:28, Tamar Christina via Gcc-patches wrote:
The regression was reported during stage-1. A patch was provided during stage 1
and the discussions around combine stalled.
The regression for AArch64 needs to be fixed in GCC 13. The hit is too big just to
"take".
So we need a way forward, even if it's stage-4.
Then it needs to be in a way that works within the design constraints of
combine.
As Segher has indicated, using a magic constant to say "this is always
cheap enough" isn't acceptable. Furthermore, what this patch changes is
combine's internal canonicalization of extensions into shift pairs.
So I think another path forward needs to be found. I don't see hacking
up expand_compound_operation is viable.
Jeff
