On 5/17/22 6:41 PM, Segher Boessenkool wrote: > On Mon, May 16, 2022 at 05:31:31PM -0500, Peter Bergner wrote: >> (define_insn "mma_<vv>" >> - [(set (match_operand:XO 0 "fpr_reg_operand" "=&d") >> - (unspec:XO [(match_operand:V16QI 1 "vsx_register_operand" "wa") >> - (match_operand:V16QI 2 "vsx_register_operand" "wa")] >> + [(set (match_operand:XO 0 "fpr_reg_operand" "=&d,&d") >> + (unspec:XO [(match_operand:V16QI 1 "vsx_register_operand" "v,?wa") >> + (match_operand:V16QI 2 "vsx_register_operand" "v,?wa")] > > You now have two "?" on alternative 1, instead of just one. This is the > same as if you had had > [(set (match_operand:XO 0 "fpr_reg_operand" "=&d,&d") > (unspec:XO [(match_operand:V16QI 1 "vsx_register_operand" "v,??wa") > (match_operand:V16QI 2 "vsx_register_operand" "v,wa")] > The "?" are per alternative, not really per operand. It won't change > much here of course, just penalise more than you perhaps expected.
Ak, ok. I think giving an extra penalty is fine here, since we really really want to use altivec regs here, so I went with the patch as is. Pushed. I'll wait a few days before backporting to GCC 12. As for GCC 11 & 10, I'll wait until someone actually has a test case that shows the same problem. I suspect a patch went into GCC 12 that changed the costs slightly and that's why we don't see the problem on the older branches. Thanks! Peter
