[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 Richard Biener changed: What|Removed |Added Target Milestone|7.3 |7.4 --- Comment #12 from Richard Biener --- GCC 7.3 is being released, adjusting target milestone.
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 Jakub Jelinek changed: What|Removed |Added Priority|P3 |P4 --- Comment #11 from Jakub Jelinek --- On the trunk the backend can deal with this using a hook. So it is a target issue if anything else needs solving.
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 --- Comment #10 from Jakub Jelinek --- Author: jakub Date: Wed Nov 29 10:31:36 2017 New Revision: 255228 URL: https://gcc.gnu.org/viewcvs?rev=255228=gcc=rev Log: PR middle-end/80929 * rtlanal.c (seq_cost): For non-single_set insns try to use insn_cost. Modified: trunk/gcc/ChangeLog trunk/gcc/rtlanal.c
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 --- Comment #9 from Jakub Jelinek --- Created attachment 42729 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42729=edit gcc8-pr80929.patch Like this untested patch.
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #8 from Jakub Jelinek --- The problem is that for non-single set PARALLELs there is just not a good guess what to do without target's help. For some targets and such insns, the best cost estimate could be maximum of the cost of both sets, for others ignoring one of them and looking only at the other one, for others the sum of both costs. E.g. the various compare + arithmetics pattern on many targets really have the cost of the arithmetics - pattern_cost even has code for that case. insn_cost (I'm not aware of insn_rtx_cost) has a way for the target to override it and therefore you could in the backend decide what to do. seq_cost doesn't, perhaps it could just call insn_cost for non-single_set insns.
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 Richard Biener changed: What|Removed |Added Target Milestone|7.2 |7.3
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 Richard Biener changed: What|Removed |Added Target Milestone|7.2 |7.3 --- Comment #8 from Richard Biener --- GCC 7.2 is being released, adjusting target milestone.
[Bug middle-end/80929] [6/7/8 Regression] Division with constant no more optimized to mult highpart
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80929 Georg-Johann Lay changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2017-07-30 Summary|[7/8 Regression] Division |[6/7/8 Regression] Division |with constant no more |with constant no more |optimized to mult highpart |optimized to mult highpart Ever confirmed|0 |1 --- Comment #7 from Georg-Johann Lay --- v4.7 generates best code: The 2 div+mod 60 are implemented as 2 mul-highpart. v6 tries to be overly smart by fusing the two divisions by 60 to one division by 3600, leaving with 1 slow divmod call *and* 2 mul-higpart for the 2 modulo 60. v8 also fuses to a slow division by 3600, but also fails to use mul-highpart for the 2nd mod 60.
