[Bug tree-optimization/56125] [4.7/4.8 Regression] -O2 -ffast-math generates bad code when dividing a double by the square of another double.

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56125



--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-28 
14:43:07 UTC ---

Author: jakub

Date: Mon Jan 28 14:43:03 2013

New Revision: 195507



URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=195507

Log:

    PR tree-optimization/56125

    * tree-ssa-math-opts.c (gimple_expand_builtin_pow): Don't optimize

    pow(x,c) into sqrt(x) * powi(x, n/2) or

    1.0 / (sqrt(x) * powi(x, abs(n/2))) if c is an integer or when

    optimizing for size.

    Don't optimize pow(x,c) into powi(x, n/3) * powi(cbrt(x), n%3) or

    1.0 / (powi(x, abs(n)/3) * powi(cbrt(x), abs(n)%3)) if 2c is an

    integer.



    * gcc.dg/pr56125.c: New test.



Added:

    trunk/gcc/testsuite/gcc.dg/pr56125.c

Modified:

    trunk/gcc/ChangeLog

    trunk/gcc/testsuite/ChangeLog

    trunk/gcc/tree-ssa-math-opts.c