https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78851
--- Comment #8 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to Richard Biener from comment #7) > I don't think that the middle-end converts pow(, int-valued) to powi anywhere > as generally the result can be off too far (maybe we could for some known > special values). For pow(x, 2.), we always get a multiplication. With -ffast-math, all pow(x, (double)int_cst) are converted to a sequence of multiplications (I just tried with pow(x,123456789) which gives a sequence of 37 multiplications at -O1 -ffast-math). But with pow(x,(double)int_var), we don't generate a call to __powidf2, even a combination of -Os -ffast-math calls __pow_finite instead.
