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. R.
