re PR tree-optimization/40921 (missed optimization: x + (-y * z * z) => x - y * z...

re PR tree-optimization/40921 (missed optimization: x + (-y * z * z) => x - y * z * z)

gcc/testsuite/ChangeLog:

2016-05-22  Kugan Vivekanandarajah  <kuganv@linaro.org>

	PR middle-end/40921
	* gcc.dg/tree-ssa/pr40921.c: New test.

gcc/ChangeLog:

2016-05-22  Kugan Vivekanandarajah  <kuganv@linaro.org>

	PR middle-end/40921
        * tree-ssa-reassoc.c (try_special_add_to_ops): New.
        (linearize_expr_tree): Call try_special_add_to_ops.
        (reassociate_bb): Convert MULT_EXPR by (-1) to NEGATE_EXPR.

From-SVN: r236564