[Bug tree-optimization/52395] New: [4.7 Regression] Alignment issue at O2

[izamyatin at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52395

             Bug #: 52395
           Summary: [4.7 Regression] Alignment issue at O2
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: izamya...@gmail.com


Created attachment 26759
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26759
Test case for the issue

I noticed that after the following commit 

commit 25b3bbad6624357c1ac6a31e0be6fca37182fb78
Author: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Fri Jan 27 14:56:54 2012 +0000

    2012-01-27  Richard Guenther  <rguent...@suse.de>

        PR tree-optimization/50444
        * tree-sra.c (build_ref_for_offset): Properly adjust the
        MEM_REF type for unaligned accesses.

        * gcc.dg/torture/pr50444.c: New testcase.


    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@183630
138bc75d-0d04-0410-961f-82ee72b054a4

 alignment of some memory references was spoiled. For attached test case I see
following:

  before commit (A32):

#(insn:TI 6 11 7 2 (set (mem:SF (reg/v/f:DI 5 di [orig:61 __x ] [61]) [2
__x_1(D)->re+0 S4 A32])
#        (const_double:SF 0.0 [0x0.0p+0])) test.cpp:13 108 {*movsf_internal}
#     (nil))
    movl    $0x00000000, (%rdi)    # 6    *movsf_internal/5    [length = 16]


  after commit (A8):

#(insn:TI 6 11 7 2 (set (mem:SF (reg/v/f:DI 5 di [orig:61 __x ] [61]) [2
__x_1(D)->re+0 S4 A8])
#        (const_double:SF 0.0 [0x0.0p+0])) test.cpp:13 108 {*movsf_internal}
#     (nil))
    movl    $0x00000000, (%rdi)    # 6    *movsf_internal/5    [length = 16]


 Compiled just with O2.

 Originally I saw this after compilation of complex_io.cc from libstdc++-v3