[Bug 1169156] GCC9 wrong handling of builtin_constant_p()

http://bugzilla.suse.com/show_bug.cgi?id=1169156 http://bugzilla.suse.com/show_bug.cgi?id=1169156#c9 --- Comment #9 from Petr Tesařík --- I'm afraid this is not quite what I mean. The issue is that __builtin_constant_p() is not tightly coupled with the knowledge of something actually being constant. So, you process code that looks (roughly) like: var = 1; if (something) cond = __builtin_constant_p(var); else { var = unknown_result(); cond = __builtin_constant_p(var); } if (cond) { d = y / var; } If cond is true, then var must be 1 (known to be constant), so GCC could optimize the expression (y / var) to (y / 1). I know this can be hard to track. -- You are receiving this mail because: You are on the CC list for the bug.