re PR tree-optimization/70840 (revisit reassoc handling of pow / powi, amend match...

re PR tree-optimization/70840 (revisit reassoc handling of pow / powi, amend match.pd for powi)

2016-04-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/70840
	* match.pd: powi(-x, y) and powi(|x|,y) -> powi(x,y) if y is even;
	Fix pow(copysign(x, y), z) -> pow(x, z) and add powi variant;
	Mark x * pow(x,c) -> pow(x,c+1) commutative.
	Add powi(x,y) * powi(z,y) -> powi(x*z,y).

From-SVN: r235566