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Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations
- From: Richard Henderson <rth at redhat dot com>
- To: Sriraman Tallam <tmsriram at google dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, David Li <davidxl at google dot com>, Cary Coutant <ccoutant at google dot com>, Ian Lance Taylor <iant at google dot com>, Paul Pluzhnikov <ppluzhnikov at google dot com>
- Date: Tue, 02 Sep 2014 13:40:50 -0700
- Subject: Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations
- Authentication-results: sourceware.org; auth=none
- References: <CAAs8Hmz8_=m1EoX=eQqX2gV+qwVOR_SO5tTCaz=MmCu3vwkpeQ at mail dot gmail dot com> <CAAs8Hmz8-tQ+BoHvSxpKErf9FG+-F7Mho9hv3FpwxLE0aBGcGQ at mail dot gmail dot com> <CAAs8HmxZJ0LdWjXb8u+yRnqjGp4y1C4GUTVQy_S7-tKaCMZVVA at mail dot gmail dot com> <CAAs8Hmw+fC9=1VDTGcOnJgPXFmMo3qtC=HqdNUvnyWrHbm51Mw at mail dot gmail dot com>
On 06/20/2014 05:17 PM, Sriraman Tallam wrote:
> Index: config/i386/i386.c
> ===================================================================
> --- config/i386/i386.c (revision 211826)
> +++ config/i386/i386.c (working copy)
> @@ -12691,7 +12691,9 @@ legitimate_pic_address_disp_p (rtx disp)
> return true;
> }
> else if (!SYMBOL_REF_FAR_ADDR_P (op0)
> - && SYMBOL_REF_LOCAL_P (op0)
> + && (SYMBOL_REF_LOCAL_P (op0)
> + || (TARGET_64BIT && ix86_copyrelocs && flag_pie
> + && !SYMBOL_REF_FUNCTION_P (op0)))
> && ix86_cmodel != CM_LARGE_PIC)
> return true;
> break;
This is the wrong place to patch.
You ought to be adjusting SYMBOL_REF_LOCAL_P, by providing a modified
TARGET_BINDS_LOCAL_P.
Note in particular that I believe that you are doing the wrong thing with weak
and COMMON symbols, in that you probably ought not force a copy reloc there.
Note the complexity of default_binds_local_p_1, and the fact that all you
really want to modify is
/* If PIC, then assume that any global name can be overridden by
symbols resolved from other modules. */
else if (shlib)
local_p = false;
near the bottom of that function.
r~