On Sat, 30 Nov 2024, Jeff Law wrote: > > > On 11/28/24 5:26 AM, Alexey Merzlyakov wrote: > > This patch adds optimization of the following patterns: > > > > (zero_extend:M (subreg:N (not:O==M (X:Q==M)))) -> > > (xor:M (zero_extend:M (subreg:N (X:M)), mask)) > > ... where the mask is GET_MODE_MASK (N). > > > > For the cases when X:M doesn't have any non-zero bits outside of mode N, > > (zero_extend:M (subreg:N (X:M)) could be simplified to just (X:M) > > and whole optimization will be: > > > > (zero_extend:M (subreg:N (not:M (X:M)))) -> > > (xor:M (X:M, mask)) > > > > Patch targets to handle code patterns like: > > not a0,a0 > > andi a0,a0,0xff > > to be optimized to: > > xori a0,a0,255
> Thanks. I've bootstrapped & regression tested this on x86_64 as well as run > it through my tester successfully. Pushed to the trunk. Hopefully no fallout > this time :-) > > jeff > > This doesn't look like an obviously generic, universal optimization. Targets that have to move a constant to a register for the xor mask, but have simple access to sub-word "not" and zero-extend, will be pessimized by having the "not" and zero-extend replaced with an xor with a constant, IIUC. brgds, H-P
