On 10/24/2013 09:24 AM, Richard Earnshaw wrote: > On 24/10/13 17:15, Richard Henderson wrote: >> On 10/24/2013 01:11 AM, Zhenqiang Chen wrote: >>>> Why would you need to encode comparisons in CCmodes? >>>> That looks like a mis-design to me. >>> >>> The CCmodes are used to check whether the result of a previous conditional >>> compare can combine with current compare. By changing it to rtx_code, I can >>> reuse current code (arm_select_dominance_cc_mode_1) to check it. >>> The CCmodes are also used to emit the "condition code" for a conditional >>> execution. E.g. >>> >>> CC1 (CC_DGEmode) = CCMP (a >= 0, b >= 0) >>> ==> cmp a, #0 >>> cmpge b, #0 >>> CC2 = CCMP ( CC1 != 0, c >= 0) >>> ==> cmpge c, #0 >>> The "ge" is from the mode of CC1 in "CC1 != 0". And the mode of CC2 is not >>> necessary the same as CC1. >> >> But since you've got the previous comparison operator, why do you need >> the same data encoded into the mode? >> >> >> r~ >> > > The branch instruction doesn't have that information, only the CC mode.
Why would the branch instruction need that information? Havn't we already validated whether the comparisons can combine? r~
