https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107294
--- Comment #6 from kargls at comcast dot net --- (In reply to mjr19 from comment #5) > But 10.1.5.2.4 says "once the interpretation of a numeric intrinsic > operation is established, the processor may evaluate any mathematically > equivalent expression, provided that the integrity of parentheses is not > violated." > > As cmplx(r)*z and cmplx(r*real(z),r*aimag(z)) are mathematically equivalent, > is a Fortran compiler not permitted to make this optimisation (unless > conforming to F90 or F95, for 10.1.5.2.4 was first introduced in F2003)? > > Furthermore, Fortran does not define how complex multiplication is to be > performed, so relying on the precise details result when multiplying signed > zeros or NaNs may be unwise. See comment #3. Type conversion occurs. If you want to get a possibly wrong answer fast, use either -Ofast or -ffast-math.
