[Bug c/63303] Pointer subtraction is broken when using -fsanitize=undefined

2018-08-26 Thread jvg1981 at aim dot com
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63303 --- Comment #20 from Joshua Green --- > "But if we don't know which pointer is greater, it gets more complicated: > ..." > > I'm not sure that this is true. For types that are larger than 1 byte, it > seems that one can do the subtraction

[Bug c/63303] Pointer subtraction is broken when using -fsanitize=undefined

2018-08-21 Thread jvg1981 at aim dot com
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63303 Joshua Green changed: What|Removed |Added CC||jvg1981 at aim dot com --- Comment #17

[Bug tree-optimization/66573] Unexpected change in static, branch-prediction cost from O1 to O2 in if-then-else.

2015-11-24 Thread jvg1981 at aim dot com
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66573 --- Comment #11 from Joshua Green --- (In reply to Segher Boessenkool from comment #10) > GCC thinks bar2 will be executed more often that bar1; the code > it generates is perfectly fine for that. > > If you think GCC's heuristics for branch

[Bug tree-optimization/66573] Unexpected change in static, branch-prediction cost from O1 to O2 in if-then-else.

2015-11-21 Thread jvg1981 at aim dot com
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66573 --- Comment #7 from Joshua Green --- (In reply to Segher Boessenkool from comment #6) > bb-reorder changes the conditional branch so that the fallthrough path > is the most likely. It now also does this for -O1. This is faster on >

[Bug tree-optimization/66573] Unexpected change in static, branch-prediction cost from O1 to O2 in if-then-else.

2015-11-21 Thread jvg1981 at aim dot com
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66573 --- Comment #9 from Joshua Green --- (In reply to Segher Boessenkool from comment #8) > GCC does some fairly involved prediction (in predict.c). It isn't > "a priori". > > > (It's also not clear HOW this could be "faster > > on essentially all

[Bug tree-optimization/66573] Unexpected change in static, branch-prediction cost from O1 to O2 in if-then-else.

2015-11-19 Thread jvg1981 at aim dot com
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66573 jvg1981 at aim dot com changed: What|Removed |Added CC||jvg1981 at aim dot com