Re: [3/7] v10: Collect alignment info

[Ian Lance Taylor <iant at google dot com>]

"H.J. Lu" <hjl.tools@gmail.com> writes:

> 2008-07-08  Joey Ye  <joey.ye@intel.com>
> 	    H.J. Lu  <hongjiu.lu@intel.com>
>
> 	* builtins.c (expand_builtin_setjmp_receiver): Replace
> 	virtual_incoming_args_rtx with
> 	crtl->args.internal_arg_pointer.
> 	(expand_builtin_apply_args_1): Likewise.
> 	(expand_builtin_longjmp): Need DRAP for stack alignment.
> 	(expand_builtin_apply): Likewise.
>
> 	* caller-save.c (setup_save_areas): Call assign_stack_local_1
> 	instead of assign_stack_local to allow alignment reduction.
>
> 	* calls.c (emit_call_1): Need DRAP for stack alignment if
> 	return pops.
> 	(expand_call): Replace virtual_incoming_args_rtx with
> 	crtl->args.internal_arg_pointer.
> 	* stmt.c (expand_nl_goto_receiver): Likewise.
>
> 	* cfgexpand.c (get_decl_align_unit): Estimate stack variable
> 	alignment and store to stack_alignment_estimated and
> 	max_used_stack_slot_alignment.
> 	(expand_one_var): Likewise.
> 	(expand_stack_alignment): New function.
> 	(tree_expand_cfg): Initialize max_used_stack_slot_alignment
> 	and stack_alignment_estimated fields in rtl_data.  Call
> 	expand_stack_alignment at end.
>
> 	* defaults.h (INCOMING_STACK_BOUNDARY): New.
> 	(MAX_STACK_ALIGNMENT): Likewise.
> 	(MAX_SUPPORTED_STACK_ALIGNMENT): Likewise.
> 	(SUPPORTS_STACK_ALIGNMENT): Likewise.
>
> 	* emit-rtl.c (gen_reg_rtx): Estimate stack alignment for
> 	stack alignment when generating virtual registers.
>
> 	* function.c (assign_stack_local): Renamed to ...
> 	(assign_stack_local_1): This.  Add a parameter to indicate
> 	if it is OK to reduce alignment.
> 	(assign_stack_local): Use it.
> 	(instantiate_new_reg): Instantiate virtual incoming args rtx
> 	to vDRAP if stack realignment and DRAP is needed.
> 	(assign_parms): Collect parameter/return type alignment and
> 	contribute to stack_alignment_estimated.
> 	(locate_and_pad_parm): Likewise.
> 	(get_arg_pointer_save_area): Replace virtual_incoming_args_rtx
> 	with crtl->args.internal_arg_pointer.
>
> 	* function.h (rtl_data): Add new field drap_reg,
> 	max_used_stack_slot_alignment, stack_alignment_estimated,
> 	stack_realign_needed, need_drap, stack_realign_processed and
> 	stack_realign_finalized.
> 	(stack_realign_fp): New macro.
> 	(stack_realign_drap): Likewise.
>
> 	* global.c (compute_regsets): Frame pointer is needed when
> 	stack is realigned.  Can eliminate frame pointer when stack is
> 	realigned and dynamic realigned argument pointer isn't used.
>
> 	* reload1.c (update_eliminables):  Frame pointer is needed
> 	when stack is realigned.
> 	(init_elim_table): Can eliminate frame pointer when stack is
> 	realigned and dynamic realigned argument pointer isn't used.
>
> 	* rtl.h (assign_stack_local_1): Declare new funtion.
>
> 	* target-def.h (TARGET_UPDATE_STACK_BOUNDARY): New.
> 	(TARGET_GET_DRAP_RTX): Likewise.
> 	(TARGET_CALLS): Add TARGET_UPDATE_STACK_BOUNDARY and
> 	TARGET_GET_DRAP_RTX.
>
> 	* target.h (gcc_target): Add update_stack_boundary and
> 	get_drap_rtx.
>
> 	* tree-vectorizer.c (vect_can_force_dr_alignment_p): Replace
> 	STACK_BOUNDARY with MAX_STACK_ALIGNMENT.
>
> 2008-07-08  Xuepeng Guo  <xuepeng.guo@intel.com>
> 	    H.J. Lu  <hongjiu.lu@intel.com>
>
> 	* dwarf2out.c (dw_fde_struct): Add stack_realignment, drap_reg,
> 	vdrap_reg, stack_realign and drap_reg_saved.
> 	(add_cfi): Don't allow redefining CFA when DRAP is used.
> 	(reg_save): Handle stack alignment.
> 	(dwarf2out_frame_debug_expr): Add rules 16-20 to handle stack
> 	alignment.  Don't generate DWARF information for (set fp sp)
> 	when DRAP is used.
> 	(dwarf2out_begin_prologue): Initialize drap_reg and vdrap_reg
> 	to INVALID_REGNUM.
> 	(int_loc_descriptor): Move prototype forward.  Also define if
> 	DWARF2_UNWIND_INFO is true.
> 	(output_cfa_loc): Handle DW_CFA_expression.
> 	(build_cfa_aligned_loc): New.
> 	(based_loc_descr): Update assert for stack realign.  For local
> 	variables, use sp+offset when stack is aligned without drap and
> 	fp+offset when stack is aligned with drap.  For arguments, use
> 	cfa+offset when drap is used to align stack.
>
> 2008-07-08  Joey Ye  <joey.ye@intel.com>
> 	    H.J. Lu  <hongjiu.lu@intel.com>
>
> 	* config/i386/i386.c (ix86_force_align_arg_pointer_string):
> 	Break long line.
> 	(ix86_gen_andsp): New.
> 	(ix86_user_incoming_stack_boundary): Likewise.
> 	(ix86_default_incoming_stack_boundary): Likewise.
> 	(ix86_incoming_stack_boundary): Likewise.
> 	(ix86_can_eliminate): Likewise.
> 	(find_drap_reg): Likewise.
> 	(ix86_update_stack_boundary): Likewise.
> 	(ix86_get_drap_rtx): Likewise.
> 	(ix86_finalize_stack_realign_flags): Likewise.
> 	(TARGET_UPDATE_STACK_BOUNDARY): Likewise.
> 	(TARGET_GET_DRAP_RTX): Likewise.
> 	(override_options): Overide option value for new options.
> 	(ix86_function_ok_for_sibcall): Remove check for
> 	force_align_arg_pointer.
> 	(ix86_handle_cconv_attribute): Likewise.
> 	(ix86_function_regparm): Likewise.
> 	(setup_incoming_varargs_64): Don't set stack_alignment_needed
> 	here.
> 	(ix86_va_start): Replace virtual_incoming_args_rtx with
> 	crtl->args.internal_arg_pointer.
> 	(ix86_select_alt_pic_regnum): Check DRAP register.
> 	(ix86_save_reg): Replace force_align_arg_pointer with drap_reg.
> 	(ix86_compute_frame_layout): Compute frame layout wrt stack
> 	realignment.
> 	(ix86_internal_arg_pointer): Just return
> 	virtual_incoming_args_rtx.
> 	(ix86_expand_prologue): Decide if stack realignment is needed
> 	and generate prologue code accordingly.
> 	(ix86_expand_epilogue): Generate epilogue code wrt stack
> 	realignment is really needed or not.
> 	
> 	* config/i386/i386.h (MAIN_STACK_BOUNDARY): New.
> 	(ABI_STACK_BOUNDARY): Likewise.
> 	(PREFERRED_STACK_BOUNDARY_DEFAULT): Likewise.
> 	(STACK_REALIGN_DEFAULT): Likewise.
> 	(INCOMING_STACK_BOUNDARY): Likewise.
> 	(MAX_STACK_ALIGNMENT): Likewise.
> 	(ix86_incoming_stack_boundary): Likewise.
> 	(FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN): Removed.
> 	(REAL_PIC_OFFSET_TABLE_REGNUM): Updated to use BX_REG.
> 	(CAN_ELIMINATE): Defined with ix86_can_eliminate.
> 	(machine_function): Remove force_align_arg_pointer.
>
> 	* config/i386/i386.md (BX_REG): New.
> 	(R13_REG): Likewise.
>
> 	* config/i386/i386.opt (mforce_drap): New.
> 	(mincoming-stack-boundary): Likewise.
> 	(mstackrealign): Add Init(-1).
>
> 	* config/i386/i386-protos.h (ix86_can_eliminate): New
>
> 2008-06-10  H.J. Lu  <hongjiu.lu@intel.com>
>
> 	* doc/extend.texi: Update force_align_arg_pointer.
>
> 	* doc/invoke.texi: Document -mincoming-stack-boundary.  Update
> 	-mstackrealign.
>
> 	* doc/tm.texi (MAX_STACK_ALIGNMENT): Add macro.
> 	(INCOMING_STACK_BOUNDARY): Likewise.
> 	(TARGET_UPDATE_STACK_BOUNDARY): New target hook.
> 	(TARGET_GET_DRAP_RTX): Likewise.

This is OK with some doc and comment changes.


> +          /* Since current internal arg pointer will won't conflict
> +	     with parameter passing regs, so no need to change stack
> +	     realignment and adjust regparm number.

"will won't" => "won't".


> +mforce-drap
> +Target Report Var(ix86_force_drap)
> +Always use Dynamic Realigned Argument Pointer (DRAP) to realign stack.

Remove the period at the end of the sentence.


> +The @code{force_align_arg_pointer} attribute may be applied to
> +individual function definitions, assuming that the runtime stack is
> +aligned according to the psABI and generating an alternate
> +prologue/epilogue that realigns the runtime stack if necessary. 
> +On the Intel x86, this supports mixing codes that keep a 4-byte aligned
> +stack, as specified by i386 psABI, with codes that need a 16-byte
> +aligned stack, as required by SSE instructions. 

I don't understand what you mean by "assuming" here.  Most people
reading those won't know what the psABI is, so don't refer to it.  The
original docs were clearer than this.  Please rewrite this to say what
you mean.


> +Realign the stack at entry.  The @option{-mstackrealign} option will
> +assume that the runtime stack is aligned according to the psABI and
> +generate an alternate prologue/epilogue that realigns the runtime stack
> +if necessary.  On the Intel x86, this supports mixing codes that keep a
> +4-byte aligned stack, as specified by i386 psABI, with codes that need
> +a 16-byte aligned stack, as required by SSE instructions.  See also the
> +attribute @code{force_align_arg_pointer}, applicable to individual
> +functions.

Here also, change the reference to the psABI to simply say that the
psABI requires.


> +@c FIXME: The default should be @code{PREFERRED_STACK_BOUNDARY}.
> +But the fix for PR 32893 indicates that we can only guarantee
> +maximum stack alignment on stack up to @code{STACK_BOUNDARY}, not
> +@code{PREFERRED_STACK_BOUNDARY}, if stack alignment isn't supported.

Does this actually look right in the resulting manual?  Don't you need
@c on every line?


> +@deftypefn {Target Hook} rtx TARGET_GET_DRAP_RTX (void)
> +Define this macro to an rtx for Dynamic Realign Argument Pointer if
> +necessary.
> +@end deftypefn

This is accurate but nearly useless for the readre.  Please expand
this to explain what the Dynamic Realign Argument Pointer is.


> +      /* Replace vitural_incoming_args_rtx to internal arg pointer here */

"vitural" => "virtual".


Thanks.

Ian