On Tue, Apr 21, 2015 at 03:13:38PM +0800, Terry Guo wrote: > > Did you fix the comment? REG_USERVAR_P and HARD_REGISTER_P can be > > set for more than just register asm. > > Sorry for missing the patch. I believe that I addressed your patch. > Please review it again to make sure my understanding is correct.
> + /* Use REG_USERVAR_P and HARD_REGISTER_P to check whether DEST is a user > + specified register, and do not eliminate such register if it is in an > + asm input. Otherwise if allow such elimination, we may break the > + register asm usage defined in GCC manual. */ > + if (REG_P (dest) && REG_USERVAR_P (dest) && HARD_REGISTER_P (dest) > + && extract_asm_operands (PATTERN (i3))) > + return 0; The "to check whether DEST is a user-specified register" part is not correct; this check can for example also match for function arguments (which are hard regs) that were combined into any "normal" user var. I don't see how we would do a better check, and disallowing combination in this case is harmless (or even good); but the comment is misleading. Segher
