https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69737
--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> --- Author: segher Date: Wed Nov 1 16:40:42 2017 New Revision: 254315 URL: https://gcc.gnu.org/viewcvs?rev=254315&root=gcc&view=rev Log: combine: Fix bug in giving up placing REG_DEAD notes (PR82683) When we have a REG_DEAD note for a reg that is set in the new I2, we drop the note on the floor (we cannot find whether to place it on I2 or on I3). But the code I added to do this has a bug and does not always actually drop it. This patch fixes it. But that on its own is too pessimistic, it turns out, and we generate worse code. One case where we do know where to place the note is if it came from I3 (it should go to I3 again). Doing this fixes all of the regressions. PR rtl-optimization/64682 PR rtl-optimization/69567 PR rtl-optimization/69737 PR rtl-optimization/82683 * combine.c (distribute_notes) <REG_DEAD>: If the new I2 sets the same register mentioned in the note, drop the note, unless it came from I3, in which case it should go to I3 again. Modified: trunk/gcc/ChangeLog trunk/gcc/combine.c
