https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70255
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |wrong-code Status|UNCONFIRMED |NEW Last reconfirmed| |2016-03-16 CC| |jsm28 at gcc dot gnu.org Version|unknown |5.2.0 Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed. The issue seems to be that you add the optimize attribute after the function definition. This causes .original to be already ;; Function foo1 (null) ;; enabled by -tree-original { double s = h + 1.0e+0; double s = h + 1.0e+0; return ((h - s) + l) + 1.0e+0; } which is probably an artifact of fully delayed folding. The optimize attribute is still applied in the end but too late. Workaround is to put double foo1(double h, double l) __attribute__((optimize("no-associative-math"))); before the definition.