[PATCH] PR11706, optimize std::pow(T, int)

[Gabriel Dos Reis]

Paolo Carlini <pcarlini@suse.de> writes:

| Richard Guenther wrote:
| 
| >Hi!
| >
| >This is a fix for the ages old PR11706 (or rather a work-around?).
| >cmath __pow_helper now recognizes constant (or small constant)
| >integer powers and dispatches to the appropriate gcc builtin in
| >these cases.  This makes the code for ::pow(x, 2), std::pow(x, 2)
| >and std::pow(x, 2.0) the same, likewise for exponents > 2 in case
| >of -ffast-math (even without -funroll-loops).
| >
| >Ok for mainline?
| >
| Maybe Gaby wants to add something here, but I seem to remember that
| we really dislike this kind of approach, calling back pow from __pow_helper
| via a cast, thus giving away the info that the exponent is integer.
| 
| And, after Zdenek nice patch, -funroll-loops should lead to optimal code.
| Does it work as expected?

Indeed.

-- Gaby