[Bug target/65103] New: [i386] GOTOFF relocation is not propagated into address expression

[Bug target/65103] New: [i386] GOTOFF relocation is not propagated into address expression

[enkovich.gnu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65103

            Bug ID: 65103
           Summary: [i386] GOTOFF relocation is not propagated into
                    address expression
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: enkovich.gnu at gmail dot com

In PIC code there are multiple cases when GOTOFF relocation is put into
register and then used in address expression instead of using relocation
directly in address expression.  Here is an example:

>cat test.c
typedef struct S
{
  int a;
  int sum;
  int delta;
} S;

S gs;
int global_opt (int max)
{
  while (gs.sum < max)
    gs.sum += gs.delta;
  return gs.a;
}
>gcc test.c -m32 -O2 -fPIE -S
>cat test.s
...
        pushl   %esi
        leal    gs@GOTOFF, %esi
        pushl   %ebx
        call    __x86.get_pc_thunk.bx
        addl    $_GLOBAL_OFFSET_TABLE_, %ebx
        movl    12(%esp), %edx
        movl    4(%esi,%ebx), %eax
        cmpl    %eax, %edx
        jle     .L4
        movl    8(%esi,%ebx), %ecx
.L3:
        addl    %ecx, %eax
        cmpl    %eax, %edx
        jg      .L3
        movl    %eax, 4(%esi,%ebx)
.L4:
        movl    gs@GOTOFF(%ebx), %eax
        popl    %ebx
        popl    %esi
        ret

A separate instruction to get gs@GOTOFF is generated in expand.  Later fwprop
propagates this constant only into memory references with zero offset and leave
register usage in all others.

Used compiler:

Target: x86_64-unknown-linux-gnu
Configured with: ../gcc/configure --enable-languages=c,c++,fortran
--disable-bootstrap --prefix=/export/users/ienkovic/ --disable-libsanitizer
Thread model: posix
gcc version 5.0.0 20150217 (experimental) (GCC)

[Bug target/65103] [i386] GOTOFF relocation is not propagated into address expression

[ienkovich at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65103

--- Comment #1 from ienkovich at gcc dot gnu.org ---
Author: ienkovich
Date: Thu Mar 12 09:53:36 2015
New Revision: 221380

URL: https://gcc.gnu.org/viewcvs?rev=221380&root=gcc&view=rev
Log:
gcc/

    PR target/65103
    * config/i386/i386.c (ix86_address_cost): Fix cost of a PIC
    register.

gcc/testsuite/

    PR target/65103
    * gcc.target/i386/pr65103-1.c: New.


Added:
    trunk/gcc/testsuite/gcc.target/i386/pr65103-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/i386.c
    trunk/gcc/testsuite/ChangeLog

[Bug target/65103] [i386] GOTOFF relocation is not propagated into address expression

[LpSolit at netscape dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65103

--- Comment #1 from Ilya Enkovich <ienkovich at gcc dot gnu.org> ---
Author: ienkovich
Date: Thu Mar 12 09:53:36 2015
New Revision: 221380

URL: https://gcc.gnu.org/viewcvs?rev=221380&root=gcc&view=rev
Log:
gcc/

    PR target/65103
    * config/i386/i386.c (ix86_address_cost): Fix cost of a PIC
    register.

gcc/testsuite/

    PR target/65103
    * gcc.target/i386/pr65103-1.c: New.


Added:
    trunk/gcc/testsuite/gcc.target/i386/pr65103-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/i386.c
    trunk/gcc/testsuite/ChangeLog

[Bug target/65103] [i386] GOTOFF relocation is not propagated into address expression

[ienkovich at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65103

--- Comment #2 from Ilya Enkovich <ienkovich at gcc dot gnu.org> ---
Author: ienkovich
Date: Wed May 13 08:29:14 2015
New Revision: 223119

URL: https://gcc.gnu.org/viewcvs?rev=223119&root=gcc&view=rev
Log:
gcc/

        PR target/65103
        * config/i386/i386.c (ix86_rtx_costs): We want to propagate
        link time constants into adress expressions and therefore set
        their cost to 0.

gcc/testsuite/

        PR target/65103
        * gcc.target/i386/pr65103-3.c: New.


Added:
    trunk/gcc/testsuite/gcc.target/i386/pr65103-3.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/i386.c
    trunk/gcc/testsuite/ChangeLog

[Bug target/65103] [i386] GOTOFF relocation is not propagated into address expression

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65103

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
           Severity|normal                      |enhancement