[Bug rtl-optimization/85376] [8 Regression] wrong code with -Og -fno-dce -fgcse -fno-tree-ccp -fno-tree-copy-prop

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85376

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Fri Apr 13 19:39:11 2018
New Revision: 259377

URL: https://gcc.gnu.org/viewcvs?rev=259377&root=gcc&view=rev
Log:
        PR rtl-optimization/85376
        * simplify-rtx.c (simplify_const_unary_operation): For CLZ and CTZ and
        zero op0, if C?Z_DEFINED_VALUE_AT_ZERO is false, return NULL_RTX
        instead of a specific value.

        * gcc.dg/pr85376.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/pr85376.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/simplify-rtx.c
    trunk/gcc/testsuite/ChangeLog