[Bug middle-end/54167] New: excessive alignment

[Bug middle-end/54167] New: excessive alignment

[drepper.fsp at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54167

             Bug #: 54167
           Summary: excessive alignment
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: drepper.fsp@gmail.com


Compile the following code:

struct c
{
  int a, b;
  /*constexpr*/ c() : a(1), b(2) { }
};

c v;


The variable v will be defined with:

    .bss
    .align 16
    .type    v, @object
    .size    v, 8
v:
    .zero    8

The variable has alignment 16!

If you uncomment the constexpr and compile with -std=gnu++11 it can be seen
that the compiler does know what the correct alignment is:

    .globl    v
    .data
    .align 4
    .type    v, @object
    .size    v, 8
v:
    .long    1
    .long    2


This happens with the current svn version as well as with 4.7.0.

[Bug target/54167] excessive alignment

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54167

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.4.7, 4.9.0
             Target|                            |x86_64
      Known to fail|                            |4.5.0, 4.8.5
          Component|middle-end                  |target
             Status|UNCONFIRMED                 |RESOLVED
           Keywords|                            |missed-optimization
         Resolution|---                         |DUPLICATE
   Target Milestone|---                         |5.0

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
In GCC 4.9.0 we produce:

        .align 4
        .type   v, @object
        .size   v, 8
v:
        .zero   8

While in GCC 5+, GCC produces:
        .align 8
        .type   v, @object
        .size   v, 8
v:
        .zero   8


The GCC 4.9.0 change was r0-127682.
The GCC 5 change was r5-5887.

Which makes this a dup of bug 61296.

*** This bug has been marked as a duplicate of bug 61296 ***