On Sun, Aug 26, 2012 at 8:11 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>> What if we just add a global variable during_combine, and the insn >> predicates can check that variable? Then we wouldn't need a new >> target hook, one that seems slightly obscure to me. > > No, in x86 case we need to look at operand constraints of the insn, > and we need to recognize and analyse the insn. This way, we can avoid > i.e. "ax_reg", "nonimm_ax_reg" and such register constraints. Please also note that with "enabled" attribute, operand constraints are dynamically changed, so predicate would need to track these changes (i.e. "*umul<mode><dwi>3_1"). BTW: I found the proposed "legitimate_combined_insn" name much more descriptive, I will update the patch accordingly. Uros.
