On Fri, 19 May 2017, Alexander Monakov wrote: > On Fri, 19 May 2017, Joseph Myers wrote: > > On Fri, 19 May 2017, Alexander Monakov wrote: > > > (to be precise, if the multiplication is done in a signed type and the > > > middle > > > constant factor was a negated power of two, the sign change needs to > > > remain: > > > > > > a * -4 * b * 2 > > > > > > needs to be transformed to > > > > > > a * -1 * b * 8 ) > > > > Shouldn't that only be the case if the middle constant was -1 and the > > outer constant was 1? If a * -4 * b is INT_MIN, a * b won't overflow and > > so a * b * -8 should be a safe transformation. > > Indeed, I should have considered the situation more carefully. Thank you for > the correction.
Feel free to sumbit a patch improving the situation (as said, preferably not in extract_muldiv). Or open an enhancement bugreport refering to the above constraints. Richard.
