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From: "markus at trippelsdorf dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel
Date: Thu, 19 Jul 2012 13:09:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54031

             Bug #: 54031
           Summary: [4.8 Regression] Revision 189607 miscompiles Linux
                    kernel
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: markus@trippelsdorf.de


Starting with revision 189607 the Linux kernel (latest git) just hangs early
during boot:

...
Kernel command line: root=PARTUUID=1E3384D0-CAE6-41BB-8CD6-4F640164EFD7
init=/sbin/minit rootflags=logbsize=256k drm_kms_helper.poll=0
PID hash table entries: 4096 (order: 3, 32768 bytes)
Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes)
Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes)
__ex_table already sorted, skipping sort
Memory: 8167084k/8912896k available (4984k kernel code, 526212k absent, 219600k
reserved, 3597k data, 440k init)
SLUB: Genslabs=15, HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
Hierarchical RCU implementation.
NR_IRQS:4352 nr_irqs:712 16
Extended CMOS year: 2000
Console: colour VGA+ 80x25
console [tty0] enabled
(hang)

3482bf1319f9e65a4783bbe9d5b59c11312888db is the first bad commit
commit 3482bf1319f9e65a4783bbe9d5b59c11312888db
Author: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Wed Jul 18 08:49:55 2012 +0000

    2012-07-18  Richard Guenther  <rguenther@suse.de>

        * tree.h (get_object_or_type_alignment): Remove.
        * builtins.c (get_object_alignment_2): New function copied from
        get_object_alignment_1.  Take extra argument to indicate whether
        we take the address of EXP.  Rework to use type alignment information
        if not, and return whether the result is an approximation or not.
        (get_object_alignment_1): Wrap around get_object_alignment_2.
        (get_pointer_alignment_1): Call get_object_alignment_2 indicating
        we take the address.
        (get_object_or_type_alignment): Remove.
        * expr.c (expand_assignment): Call get_object_alignment.
        (expand_expr_real_1): Likewise.