Created attachment 484920 [details] Output of emerge --info '=www-client/firefox-54.0.1::gentoo' I've been waiting to see if anyone else had this problem, though it doesn't seem like it. Haven't had this problem before. As the buildlog is 13MB in size, I'll upload it to 0x0.st (or another host if requested) : https://0x0.st/Gly.bin
Created attachment 484922 [details] Output of emerge -pqv '=www-client/firefox-54.0.1::gentoo'
Created attachment 484924 [details] Build environment from /var/tmp/portage/www-client/firefox-54.0.1/temp/environment
That should be bug #617690 gcc 6.3.0 + pgo.
The patch in the linked bug seems to have worked, so I'm left to assume so. Thank you! *** This bug has been marked as a duplicate of bug 617690 ***