[PATCH 4/5] Generalise invalid_mode_change_p

[Jeff Law]

On 09/18/14 04:25, Richard Sandiford wrote:
> This is the main patch for the bug.  We should treat a register as invalid
> for a mode change if simplify_subreg_regno cannot provide a new register
> number for the result.  We should treat a class as invalid for a mode change
> if all registers in the class are invalid.  This is an extension of the old
> CANNOT_CHANGE_MODE_CLASS-based check (simplify_subreg_regno checks C_C_C_M).
>
> I forgot to say that the patch is a prerequisite to removing aarch64's
> C_C_C_M.  There are other prerequisites too, but removing C_C_C_M without
> this patch caused regressions in the existing testsuite, which is why no
> new tests are needed.
>
>
> gcc/
> 	* hard-reg-set.h: Include hash-table.h.
> 	(target_hard_regs): Add a finalize method and a x_simplifiable_subregs
> 	field.
> 	* target-globals.c (target_globals::~target_globals): Handle
> 	hard_regs->finalize.
> 	* rtl.h (subreg_shape): New structure.
> 	(shape_of_subreg): New function.
> 	(simplifiable_subregs): Declare.
> 	* reginfo.c (simplifiable_subreg): New structure.
> 	(simplifiable_subregs_hasher): Likewise.
> 	(simplifiable_subregs): New function.
> 	(invalid_mode_changes): Delete.
> 	(alid_mode_changes, valid_mode_changes_obstack): New variables.
> 	(record_subregs_of_mode): Remove subregs_of_mode parameter.
> 	Record valid mode changes in valid_mode_changes.
> 	(find_subregs_of_mode): Remove subregs_of_mode parameter.
> 	Update calls to record_subregs_of_mode.
> 	(init_subregs_of_mode): Remove invalid_mode_changes and bitmap
> 	handling.  Initialize new variables.  Update call to
> 	find_subregs_of_mode.
> 	(invalid_mode_change_p): Check new variables instead of
> 	invalid_mode_changes.
> 	(finish_subregs_of_mode): Finalize new variables instead of
> 	invalid_mode_changes.
> 	(target_hard_regs::finalize): New function.
> 	* ira-costs.c (print_allocno_costs): Call invalid_mode_change_p
> 	even when CLASS_CANNOT_CHANGE_MODE is undefined.
>
> Index: gcc/rtl.h
> ===================================================================
> --- gcc/rtl.h	2014-09-15 11:55:40.459855161 +0100
> +++ gcc/rtl.h	2014-09-15 12:26:21.249077760 +0100
> +/* Return the shape of a SUBREG rtx.  */
> +
> +static inline subreg_shape
> +shape_of_subreg (const_rtx x)
> +{
> +  return subreg_shape (GET_MODE (SUBREG_REG (x)),
> +		       SUBREG_BYTE (x), GET_MODE (x));
> +}
> +
Is there some reason you don't have a constructor that accepts a 
const_rtx?

OK for the trunk.

jeff