(Dropping gcc@ and people known to subscribe to gcc-patches
from the CC.)
Sorry for the drive-by review, but...
On Fri, 22 Aug 2014, Ilya Enkovich wrote:
> Hi,
>
> On Cauldron 2014 we had a couple of talks about relaxation of
> ebx usage in 32bit PIC mode. It was decided that the best
> approach would be to not fix ebx register, use speudo register
> for GOT base address and let allocator do the rest. This should
> be similar to how clang and icc work with GOT base address.
> I've been working for some time on such patch and now want to
> share my results.
...did you send the right version of the patch?
This one uses the RTX-returning hook only in boolean tests,
unless I misread.
Using the return value in boolean tests (non/NULL) here:
> diff --git a/gcc/calls.c b/gcc/calls.c
> index 4285ec1..85dae6b 100644
> --- a/gcc/calls.c
> +++ b/gcc/calls.c
> @@ -1122,6 +1122,14 @@ initialize_argument_information (int num_actuals
> ATTRIBUTE_UNUSED,
> call_expr_arg_iterator iter;
> tree arg;
>
> + if (targetm.calls.implicit_pic_arg (fndecl ? fndecl : fntype))
...
> + /* Add implicit PIC arg. */
> + if (targetm.calls.implicit_pic_arg (fndecl ? fndecl : fntype))
> + num_actuals++;
...
> + if (targetm.calls.implicit_pic_arg (fndecl ? fndecl : fntype))
but:
> +/* Return reg in which implicit PIC base address
> + arg is passed. */
> +static rtx
> +ix86_implicit_pic_arg (const_tree fntype_or_decl ATTRIBUTE_UNUSED)
...
> +#undef TARGET_IMPLICIT_PIC_ARG
> +#define TARGET_IMPLICIT_PIC_ARG ix86_implicit_pic_arg
> #undef TARGET_FUNCTION_ARG_BOUNDARY
and:
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -3967,6 +3967,12 @@ If @code{TARGET_FUNCTION_INCOMING_ARG} is not defined,
> @code{TARGET_FUNCTION_ARG} serves both purposes.
> @end deftypefn
>
> +@deftypefn {Target Hook} rtx TARGET_IMPLICIT_PIC_ARG (const_tree
> @var{fntype_or_decl})
> +This hook returns register holding PIC base address for functions
> +which do not fix hard register but handle it similar to function arg
> +assigning a virtual reg for it.
> +@end deftypefn
Also, the contains_symbol_ref removal seems like an independent
cleanup-patch.
> index a458380..63d2be5 100644
> --- a/gcc/var-tracking.c
> +++ b/gcc/var-tracking.c
> @@ -661,7 +661,6 @@ static bool variable_different_p (variable, variable);
> static bool dataflow_set_different (dataflow_set *, dataflow_set *);
> static void dataflow_set_destroy (dataflow_set *);
>
> -static bool contains_symbol_ref (rtx);
brgds, H-P
