[Bug tree-optimization/86749] [9 Regression] Gcc miscompiles at -O3 with sse4 on valid code

["rsandifo at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86749

--- Comment #2 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
Author: rsandifo
Date: Wed Aug  1 14:40:35 2018
New Revision: 263213

URL: https://gcc.gnu.org/viewcvs?rev=263213&root=gcc&view=rev
Log:
Fix over-widening handling of COND_EXPRs (PR 86749)

This PR is a wrong-code bug caused by the over-widening support.
The minimum input precisions for a COND_EXPR are supposed to apply
only to the "then" and "else" values, but here we were applying
them to the operands of a nested COND_EXPR comparison instead.

2018-08-01  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
        PR tree-optimization/86749
        * tree-vect-patterns.c (vect_determine_min_output_precision_1):
        If the lhs is used in a COND_EXPR, check that it is being used
        as the "then" or "else" value.

gcc/testsuite/
        PR tree-optimization/86749
        * gcc.dg/vect/pr86749.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/vect/pr86749.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-vect-patterns.c