Re: [PATCH] PR rtl-optimization/32219: optimizer causes wrong code in pic/hidden/weak symbol checking

[Jack Howarth <howarth dot at dot gcc at gmail dot com>]

H.J.,
   This last version of the patch bootstraps and passes the test suite
without regressions on x86_64-apple-darwin14.

https://gcc.gnu.org/ml/gcc-testresults/2015-02/msg00912.html

Thanks for fixing this.
           Jack

On Sat, Feb 7, 2015 at 11:45 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Sat, Feb 07, 2015 at 07:56:06AM -0800, H.J. Lu wrote:
>> On Sat, Feb 07, 2015 at 10:11:01AM -0500, Jack Howarth wrote:
>> > H.J,,
>> >     Unfortunately, the answer is yes. This patch still introduces
>> > regressions in the g++ test suite.l These are all some form of...
>> >
>>
>> It looks like Darwin depends on the old behavior of
>> default_binds_local_p_1.  Please try this patch.
>>
>
> Here is an updated patch.
>
>
> H.J.
> From d010cd1ddf866f8e10fe7ad2cf483b5a872bc6ea Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Thu, 5 Feb 2015 14:28:58 -0800
> Subject: [PATCH] Handle symbol visibility/locality for PIE/PIC
>
> If a hidden weak symbol isn't defined in the TU, we can't assume it will
> be defined in another TU at link time.  It makes a difference in code
> generation when compiling for PIC. If we assume that a hidden weak
> undefined symbol is local, the address checking may be optimized out and
> leads to the wrong code.  This means that a symbol with user specified
> visibility is local only if it is locally resolved or defined, not weak
> or not compiling for PIC.  When symbol visibility is specified in the
> source, we should always output symbol visibility even if symbol isn't
> local to the TU.
>
> If a global data symbol is defined in the TU, it is always local to the
> executable, regardless if it is a common symbol or not.  If we aren't
> compiling for shared library, locally defined global data symbol binds
> locally.
>
> Since some targets call default_binds_local_p_1 directly and depend on
> the old behavior of default_binds_local_p_1.  This patch renames
> default_binds_local_p_1 to default_binds_local_p_2 and implements the
> new behavior in default_binds_local_p_2 controlled by a variable.
> The old behavior remains with default_binds_local_p_1.
>
> gcc/
>
>         PR rtl-optimization/32219
>         * cgraphunit.c (varpool_node::finalize_decl): Set definition
>         first before calling notice_global_symbol so that it is
>         available to notice_global_symbol.
>         * varasm.c (default_binds_local_p_1): Renamed to ...
>         (default_binds_local_p_2): This.  Resolve defined data symbol
>         locally if not building shared library.  Resolve symbol with
>         user specified visibility locally only if it is locally resolved
>         or defined, not weak or not compiling for PIC.
>         (default_binds_local_p): Replace default_binds_local_p_1 with
>         default_binds_local_p_2.
>         (default_binds_local_p_1): Call default_binds_local_p_2.
>         (default_elf_asm_output_external): Always output visibility
>         specified in the source.
>
> gcc/testsuite/
>
>         PR rtl-optimization/32219
>         * gcc.dg/visibility-22.c: New test.
>         * gcc.dg/visibility-23.c: Likewise.
>         * gcc.target/i386/pr32219-1.c: Likewise.
>         * gcc.target/i386/pr32219-2.c: Likewise.
>         * gcc.target/i386/pr32219-3.c: Likewise.
>         * gcc.target/i386/pr32219-4.c: Likewise.
>         * gcc.target/i386/pr32219-5.c: Likewise.
>         * gcc.target/i386/pr32219-6.c: Likewise.
>         * gcc.target/i386/pr32219-7.c: Likewise.
>         * gcc.target/i386/pr32219-8.c: Likewise.
>         * gcc.target/i386/pr64317.c: Expect GOTOFF relocation instead
>         of GOT relocation.
> ---
>  gcc/cgraphunit.c                          |  4 +-
>  gcc/testsuite/gcc.dg/visibility-22.c      | 17 +++++++++
>  gcc/testsuite/gcc.dg/visibility-23.c      | 15 ++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-1.c | 16 ++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-2.c | 16 ++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-3.c | 17 +++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-4.c | 17 +++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-5.c | 16 ++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-6.c | 16 ++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-7.c | 17 +++++++++
>  gcc/testsuite/gcc.target/i386/pr32219-8.c | 17 +++++++++
>  gcc/testsuite/gcc.target/i386/pr64317.c   |  2 +-
>  gcc/varasm.c                              | 61 +++++++++++++++++++++----------
>  13 files changed, 209 insertions(+), 22 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/visibility-22.c
>  create mode 100644 gcc/testsuite/gcc.dg/visibility-23.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-1.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-2.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-3.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-4.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-5.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-6.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-7.c
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr32219-8.c
>
> diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
> index 35b244e..71367a3 100644
> --- a/gcc/cgraphunit.c
> +++ b/gcc/cgraphunit.c
> @@ -792,8 +792,10 @@ varpool_node::finalize_decl (tree decl)
>
>    if (node->definition)
>      return;
> -  notice_global_symbol (decl);
> +  /* Set definition first before calling notice_global_symbol so that
> +     it is available to notice_global_symbol.  */
>    node->definition = true;
> +  notice_global_symbol (decl);
>    if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl)
>        /* Traditionally we do not eliminate static variables when not
>          optimizing and when not doing toplevel reoder.  */
> diff --git a/gcc/testsuite/gcc.dg/visibility-22.c b/gcc/testsuite/gcc.dg/visibility-22.c
> new file mode 100644
> index 0000000..52f59be
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/visibility-22.c
> @@ -0,0 +1,17 @@
> +/* PR target/32219 */
> +/* { dg-do run } */
> +/* { dg-require-visibility "" } */
> +/* { dg-options "-O2 -fPIC" { target fpic } } */
> +/* This test requires support for undefined weak symbols.  This support
> +   is not available on hppa*-*-hpux*.  The test is skipped rather than
> +   xfailed to suppress the warning that would otherwise arise.  */
> +/* { dg-skip-if "" { "hppa*-*-hpux*" "*-*-aix*" "*-*-darwin*" } "*" { "" } }  */
> +
> +extern void foo () __attribute__((weak,visibility("hidden")));
> +int
> +main()
> +{
> +  if (foo)
> +    foo ();
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/visibility-23.c b/gcc/testsuite/gcc.dg/visibility-23.c
> new file mode 100644
> index 0000000..0fa9ef4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/visibility-23.c
> @@ -0,0 +1,15 @@
> +/* PR target/32219 */
> +/* { dg-do compile } */
> +/* { dg-require-visibility "" } */
> +/* { dg-final { scan-hidden "foo" } } */
> +/* { dg-options "-O2 -fPIC" { target fpic } } */
> +/* { dg-skip-if "" { "hppa*-*-hpux*" "*-*-aix*" "*-*-darwin*" } "*" { "" } }  */
> +
> +extern void foo () __attribute__((weak,visibility("hidden")));
> +int
> +main()
> +{
> +  if (foo)
> +    foo ();
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-1.c b/gcc/testsuite/gcc.target/i386/pr32219-1.c
> new file mode 100644
> index 0000000..5bd80a0
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-1.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpie" } */
> +
> +/* Common symbol with -fpie.  */
> +int xxx;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-2.c b/gcc/testsuite/gcc.target/i386/pr32219-2.c
> new file mode 100644
> index 0000000..0cf2eb5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-2.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpic" } */
> +
> +/* Common symbol with -fpic.  */
> +int xxx;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-3.c b/gcc/testsuite/gcc.target/i386/pr32219-3.c
> new file mode 100644
> index 0000000..911f2a5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-3.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpie" } */
> +
> +/* Weak common symbol with -fpie.  */
> +__attribute__((weak))
> +int xxx;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-4.c b/gcc/testsuite/gcc.target/i386/pr32219-4.c
> new file mode 100644
> index 0000000..3d43439
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-4.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpic" } */
> +
> +/* Weak common symbol with -fpic.  */
> +__attribute__((weak))
> +int xxx;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-5.c b/gcc/testsuite/gcc.target/i386/pr32219-5.c
> new file mode 100644
> index 0000000..ee7442e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-5.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpie" } */
> +
> +/* Initialized symbol with -fpie.  */
> +int xxx = -1;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-6.c b/gcc/testsuite/gcc.target/i386/pr32219-6.c
> new file mode 100644
> index 0000000..f261433
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-6.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpic" } */
> +
> +/* Initialized symbol with -fpic.  */
> +int xxx = -1;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-7.c b/gcc/testsuite/gcc.target/i386/pr32219-7.c
> new file mode 100644
> index 0000000..12aaf72
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-7.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpie" } */
> +
> +/* Weak initialized symbol with -fpie.  */
> +__attribute__((weak))
> +int xxx = -1;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr32219-8.c b/gcc/testsuite/gcc.target/i386/pr32219-8.c
> new file mode 100644
> index 0000000..2e4fba0
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr32219-8.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpic" } */
> +
> +/* Weak initialized symbol with -fpic.  */
> +__attribute__((weak))
> +int xxx = -1;
> +
> +int
> +foo ()
> +{
> +  return xxx;
> +}
> +
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx\\(%rip\\), %eax" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "xxx@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "movl\[ \t\]xxx@GOTOFF\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]xxx@GOT\\(%\[^,\]*\\), %eax" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr64317.c b/gcc/testsuite/gcc.target/i386/pr64317.c
> index 33f5b5d..32969fc 100644
> --- a/gcc/testsuite/gcc.target/i386/pr64317.c
> +++ b/gcc/testsuite/gcc.target/i386/pr64317.c
> @@ -1,7 +1,7 @@
>  /* { dg-do compile { target { *-*-linux* && ia32 } } } */
>  /* { dg-options "-O2 -fpie" } */
>  /* { dg-final { scan-assembler "addl\[ \\t\]+\[$\]_GLOBAL_OFFSET_TABLE_, %ebx" } } */
> -/* { dg-final { scan-assembler "movl\[ \\t\]+c@GOT\[(\]%ebx\[)\]" } } */
> +/* { dg-final { scan-assembler "movl\[ \\t\]+c@GOTOFF\[(\]%ebx\[)\]" } } */
>  /* { dg-final { scan-assembler-not "movl\[ \\t\]+\[0-9]+\[(\]%esp\[)\], %ebx" } } */
>  long c;
>
> diff --git a/gcc/varasm.c b/gcc/varasm.c
> index eb65b1f..e4bc2c1 100644
> --- a/gcc/varasm.c
> +++ b/gcc/varasm.c
> @@ -6802,17 +6802,8 @@ resolution_local_p (enum ld_plugin_symbol_resolution resolution)
>           || resolution == LDPR_RESOLVED_EXEC);
>  }
>
> -/* Assume ELF-ish defaults, since that's pretty much the most liberal
> -   wrt cross-module name binding.  */
> -
> -bool
> -default_binds_local_p (const_tree exp)
> -{
> -  return default_binds_local_p_1 (exp, flag_shlib);
> -}
> -
> -bool
> -default_binds_local_p_1 (const_tree exp, int shlib)
> +static bool
> +default_binds_local_p_2 (const_tree exp, bool shlib, bool weak_dominate)
>  {
>    bool local_p;
>    bool resolved_locally = false;
> @@ -6826,11 +6817,18 @@ default_binds_local_p_1 (const_tree exp, int shlib)
>        && (TREE_STATIC (exp) || DECL_EXTERNAL (exp)))
>      {
>        varpool_node *vnode = varpool_node::get (exp);
> -      if (vnode && (resolution_local_p (vnode->resolution) || vnode->in_other_partition))
> -       resolved_locally = true;
> -      if (vnode
> -         && resolution_to_local_definition_p (vnode->resolution))
> -       resolved_to_local_def = true;
> +      /* If not building shared library, common or initialized symbols
> +        are also resolved locally, regardless they are weak or not if
> +        weak_dominate is true.  */
> +      if (vnode)
> +       {
> +         if ((weak_dominate && !shlib && vnode->definition)
> +             || vnode->in_other_partition
> +             || resolution_local_p (vnode->resolution))
> +           resolved_locally = true;
> +         if (resolution_to_local_definition_p (vnode->resolution))
> +           resolved_to_local_def = true;
> +       }
>      }
>    else if (TREE_CODE (exp) == FUNCTION_DECL && TREE_PUBLIC (exp))
>      {
> @@ -6859,9 +6857,15 @@ default_binds_local_p_1 (const_tree exp, int shlib)
>    else if (! TREE_PUBLIC (exp))
>      local_p = true;
>    /* A variable is local if the user has said explicitly that it will
> -     be.  */
> +     be and it is resolved or defined locally, not compiling for PIC,
> +     not weak or weak_dominate is false.  */
>    else if ((DECL_VISIBILITY_SPECIFIED (exp)
>             || resolved_to_local_def)
> +          && (!weak_dominate
> +              || resolved_locally
> +              || !flag_pic
> +              || !DECL_EXTERNAL (exp)
> +              || !DECL_WEAK (exp))
>            && DECL_VISIBILITY (exp) != VISIBILITY_DEFAULT)
>      local_p = true;
>    /* Variables defined outside this object might not be local.  */
> @@ -6881,8 +6885,9 @@ default_binds_local_p_1 (const_tree exp, int shlib)
>    else if (shlib)
>      local_p = false;
>    /* Uninitialized COMMON variable may be unified with symbols
> -     resolved from other modules.  */
> +     resolved from other modules unless weak_dominate is true.  */
>    else if (DECL_COMMON (exp)
> +          && !weak_dominate
>            && !resolved_locally
>            && (DECL_INITIAL (exp) == NULL
>                || (!in_lto_p && DECL_INITIAL (exp) == error_mark_node)))
> @@ -6895,6 +6900,21 @@ default_binds_local_p_1 (const_tree exp, int shlib)
>    return local_p;
>  }
>
> +/* Assume ELF-ish defaults, since that's pretty much the most liberal
> +   wrt cross-module name binding.  */
> +
> +bool
> +default_binds_local_p (const_tree exp)
> +{
> +  return default_binds_local_p_2 (exp, flag_shlib != 0, true);
> +}
> +
> +bool
> +default_binds_local_p_1 (const_tree exp, int shlib)
> +{
> +  return default_binds_local_p_2 (exp, shlib != 0, false);
> +}
> +
>  /* Return true when references to DECL must bind to current definition in
>     final executable.
>
> @@ -7445,9 +7465,10 @@ default_elf_asm_output_external (FILE *file ATTRIBUTE_UNUSED,
>  {
>    /* We output the name if and only if TREE_SYMBOL_REFERENCED is
>       set in order to avoid putting out names that are never really
> -     used. */
> +     used.   Always output visibility specified in the source.  */
>    if (TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl))
> -      && targetm.binds_local_p (decl))
> +      && (DECL_VISIBILITY_SPECIFIED (decl)
> +         || targetm.binds_local_p (decl)))
>      maybe_assemble_visibility (decl);
>  }
>
> --
> 2.1.0
>