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Date: Wed, 01 Dec 2004 16:46:00 -0000
From: "markus at oberhumer dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Message-ID: <20041201164559.18759.markus@oberhumer.com>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug target/18759] New: [x86] using both -fomit-frame-pointer and -momit-leaf-frame-pointer enables frame pointers for non-leaf functions
X-Bugzilla-Reason: CC
X-SW-Source: 2004-12/txt/msg00145.txt.bz2
List-Id: <gcc-bugs.sourceware.org>

Using both -fomit-frame-pointer and -momit-leaf-frame-pointer _enables_ frame
pointers for non-leaf functions.
 
> cat x.c
int foo(void) { return 0; }
int bar(void) { return foo() + 1; }

> gcc-3.4 -O2 -fomit-frame-pointer -c x.c && objdump -d x.o

  [...]
00000010 <bar>:
  10:   e8 fc ff ff ff          call   11 <bar+0x1>
  15:   40                      inc    %eax
  16:   c3                      ret
  [...]

> gcc-3.4 -O2 -fomit-frame-pointer -momit-leaf-frame-pointer -c x.c && objdump
-d x.o

  [...]
00000010 <bar>:
  10:   55                      push   %ebp
  11:   89 e5                   mov    %esp,%ebp
  13:   e8 fc ff ff ff          call   14 <bar+0x4>
  18:   5d                      pop    %ebp
  19:   40                      inc    %eax
  1a:   c3                      ret
  [...]



This check in i386.c ix86_frame_pointer_required() could be the cause:

  /* In override_options, TARGET_OMIT_LEAF_FRAME_POINTER turns off
     the frame pointer by default.  Turn it back on now if we've not
     got a leaf function.  */
  if (TARGET_OMIT_LEAF_FRAME_POINTER
      && (!current_function_is_leaf))
    return 1;

-- 
           Summary: [x86] using both -fomit-frame-pointer and -momit-leaf-
                    frame-pointer enables frame pointers for non-leaf
                    functions
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: markus at oberhumer dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i386-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18759