https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79778
Bug ID: 79778 Summary: [7 regression] missed optimization causes linux kernel build failure since r245135 Product: gcc Version: 7.0.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: arnd at linaro dot org Target Milestone: --- With the latest gcc-7.0.1 snapshot, I got lots of these failures building random linux kernel configurations: kernel/built-in.o: In function `update_wall_time': (.text+0x418a0): undefined reference to `____ilog2_NaN' Variations of this symptom have happened in the past, e.g. pr36359, pr78653, pr78879, pr49642, pr72785, but for all I can tell, this one is slightly different again. I have bisected the problem to r245135, and have confirmed that reverting this on top of r245806 (today's HEAD commit) fixes the problem for builds that ran into this on my test box.