On 5/17/23 02:57, liuhongt wrote:
r14-172-g0368d169492017 replaces GENERAL_REGS with NO_REGS in cost calculation when the preferred register class are not known yet. It regressed powerpc PR109610 and PR109858, it looks too aggressive to use NO_REGS when mode can be allocated with GENERAL_REGS. The patch takes a step back, still use GENERAL_REGS when hard_regno_mode_ok for mode and GENERAL_REGS, otherwise uses NO_REGS. Kewen confirmed the patch fixed PR109858, I vefiried it also fixed PR109610. Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}. No big performance impact for SPEC2017 on icelake server. Ok for trunk? gcc/ChangeLog: * ira-costs.cc (scan_one_insn): Only use NO_REGS in cost calculation when !hard_regno_mode_ok for GENERAL_REGS and mode, otherwise still use GENERAL_REGS.
Thank you for the patch. It looks good for me. It is ok to commit it into the trunk.