[Bug tree-optimization/77673] [5/6/7 Regression] 4-byte load generated instead of 1-byte load, possibly reading past the end of object

["thopre01 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77673

--- Comment #10 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Author: thopre01
Date: Wed Dec 14 10:07:01 2016
New Revision: 243637

URL: https://gcc.gnu.org/viewcvs?rev=243637&root=gcc&view=rev
Log:
Fix PR77673: bswap loads passed end of object

2016-12-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    Backport from mainline
    2016-11-25  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR tree-optimization/77673
    * tree-ssa-math-opts.c (struct symbolic_number): Add new src field.
    (init_symbolic_number): Initialize src field from src parameter.
    (perform_symbolic_merge): Select most dominated statement as the
    source statement.  Set src field of resulting n structure from the
    input src with the lowest address.
    (find_bswap_or_nop): Rename source_stmt into ins_stmt.
    (bswap_replace): Rename src_stmt into ins_stmt.  Initially get source
    of load from src field rather than insertion statement.  Cancel
    optimization if statement analyzed is not dominated by the insertion
    statement.
    (pass_optimize_bswap::execute): Rename src_stmt to ins_stmt.  Compute
    dominance information.

    gcc/testsuite/
    PR tree-optimization/77673
    * gcc.dg/pr77673.c: New test.

Added:
    branches/gcc-5-branch/gcc/testsuite/gcc.dg/pr77673.c
Modified:
    branches/gcc-5-branch/gcc/ChangeLog
    branches/gcc-5-branch/gcc/testsuite/ChangeLog
    branches/gcc-5-branch/gcc/tree-ssa-math-opts.c