[Bug tree-optimization/81396] [7/8 Regression] Optimization of reading Little-Endian 64-bit number with portable code has a regression

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81396

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Mon Jul 17 08:14:16 2017
New Revision: 250257

URL: https://gcc.gnu.org/viewcvs?rev=250257&root=gcc&view=rev
Log:
        PR tree-optimization/81396
        * tree-ssa-math-opts.c (struct symbolic_number): Add n_ops field.
        (init_symbolic_number): Initialize it to 1.
        (perform_symbolic_merge): Add n_ops from both operands into the new
        n_ops.
        (find_bswap_or_nop): Don't consider n->n == cmpnop computations
        without base_addr as useless if they need more than one operation.
        (bswap_replace): Handle !bswap case for NULL base_addr.

        * gcc.dg/tree-ssa/pr81396.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr81396.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-math-opts.c