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Re: [PATCH i386] Allow sibcalls in no-PLT PIC


Ping?  Any comment about this patch?

On Mon, 4 May 2015, Alexander Monakov wrote:

> With -fno-plt, we don't have to reject even direct calls as sibcall
> candidates.
> 
> This patch depends on '-fplt' flag that is introduced in another patch.
> 
> This patch requires that with -fno-plt all sibcall candidates go through
> prepare_call_address that transforms the call to a GOT lookup.
> 
> OK?
> 	* config/i386/i386.c (ix86_function_ok_for_sibcall): Check flag_plt.
> 
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index f29e053..b734350 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -5448,12 +5448,13 @@ ix86_function_ok_for_sibcall (tree decl, tree exp)
>    /* If we are generating position-independent code, we cannot sibcall
>       optimize any indirect call, or a direct call to a global function,
>       as the PLT requires %ebx be live. (Darwin does not have a PLT.)  */
>    if (!TARGET_MACHO
>        && !TARGET_64BIT
>        && flag_pic
> +      && flag_plt
>        && (decl && !targetm.binds_local_p (decl)))
>      return false;
>  
>    /* If we need to align the outgoing stack, then sibcalling would
>       unalign the stack, which may break the called function.  */
>    if (ix86_minimum_incoming_stack_boundary (true)
> 


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