[lra] patch mostly implementing pseudo live range split

[Vladimir Makarov]

This patch contains a part of my several last weeks work on LRA.

1. The major change is to add pseudo live range split transformation to the
    existing inheritance transformations.  The idea is to create a new
    split pseudo, add save/restore code using the split pseudo in EBB
    for a pseudo got hard register which intersects a few reload
    pseudos live ranges with high register pressure, and assign the
    original pseudo hard register to the split pseudo.  The
    transformation is undone if the split pseudo did not change his hard
    register or was not spilled in the assignment pass which is between
    the passes doing and undoing inheritance/split transformations.

    This new functionality of LRA (pseudo range splitting) permits to
    move a separate caller saves pass into inheritance/split
    transformation pass.  This makes LRA smaller and a bit faster.

2. The patch adds the code for correct update of debug insns for
    inheritance/split transformations.  So I believe that now LRA deals
    with debug info not worse than reload pass.

3. The patch rewrite the way of dealing with the secondary memory
    moves in constraint pass of LRA.  Previously we generated secondary
    moves if macro SECONDARY_MEMORY_NEEDED says so.  Unfortunately, the
    macro is usually defined inaccurately.  Therefore now we emit
    secondary moves only if insn constraints are not satisfied (in
    other words we need reloads for given move).  This change permitted
    to solve last degradations on GCC testsuite for x86-64/x86 in
    comparison when the reload pass is used.

4. The patch also rewrites code for dealing with secondary memory
    moves in PPC.  PPC port is single one allocating explicitly stack
    slot for secondary memory of given mode through using macro
    SECONDARY_MEMORY_NEEDED_RTX.  The patch rejects this approach for
    LRA and uses a pseudo for secondary memory and this pseudo gets
    memory as in standard mechanism for spilling in LRA.  This permits
    reuse the slots allocated for secondary memory for other spilled
    pseudo decreasing allocated stack slot size in some case.  This
    change will permit to remove SECONDARY_MEMORY_NEEDED_RTX (as many
    others) if LRA is in GCC finally.

5. There are other small and insignificant changes in the patch mostly
    to fix some bugs and testsuite degradations.

The patch was successfully bootstrapped on x86/x86-64, ppc64, and
itanium.  Arm bootstrap is still going.

Committed to LRA branch as rev. 181820.

2011-11-29  Vladimir Makarov<vmakarov@redhat.com>

	* config/rs6000/rs6000.h (SECONDARY_MEMORY_NEEDED_MODE): New
	macro.

	* config/rs6000/rs6000-protos.h
	(rs6000_secondary_memory_needed_mode): New prototype.

	* config/rs6000/rs6000.c (rs6000_emit_move): Rewrite the code for
	LRA for emitting secondary memory moves based on class of the
	pseudo denoting the secondary memory.
	(rs6000_secondary_memory_needed_mode): New function.
	(rs6000_check_sdmode): Do nothing for LRA.

	* config/i386/i386.c (inline_secondary_memory_needed): Switch off
	an assert for LRA.

	* lra-int.h (lra_split_pseudos): New external.

	* lra-assigns.c (lra_setup_reg_renumber): Add code for printing
	split pseudos.
	(assign_candidates_bitmap, assign_candidates, assigned_pseudos):
	Remove.
	(spill_for): Add code for dealing with the split pseudos.
	(assign_by_spills): Ditto.

	* lra.c (lra_split_pseudos): New bitmap.
	(lra): Initialize and finalize lra_split_pseudos.  Remove call of
	lra_save_restore.  Always do inheritance/split pass on the first
	iteration when caller_save_needed.

	* lra-constraints.c (lra_secondary_memory): Remove.
	(get_secondary_mem): Ditto.
	(get_reload_reg): Make value of output reload pseudo unique.
	(emit_secondary_memory_move): Rename emit_spill_move.  Process
	subregs.
	(check_and_process_move): Add new argument.  Don't emit secondary
	memory moves, only report them.  Make values of scratch and
	secondary pseudos unique.
	(curr_insn_transform): Emit secondary memory moves only if insn
	does not satisfy all constraints.
	(MAX_RELOAD_INSNS_NUMBER): Increase it to LRA_MAX_INSN_RELOADS.
	(lra_contraints_init): Remove code initializing
	lra_secondary_memory.
	(usage_insns_check): Remove.
	(reloads_num, calls_num): New.
	(struct usage_insns): New.
	(usage_insns): Change the type.
	(inherit_reload_reg): Improve formatting.  Add more asserts.
	(need_for_call_save_p, need_for_split_p, choose_split_class): New
	functions.
	(split_pseudo): New function.
	(update_ebb_live_info): Process insns even if EBB contains one BB.
	(get_live_on_other_edges, get_non_debug_insn): New functions.
	(temp_bitmap): New bitmap.
	(add_next_usage_insn): New function.
	(inherit_in_ebb): Change the prototype.  Add code for pseudo range
	splitting.
	(lra_inheritance): Call update_ebb_live_info if the changes were
	made in inherit_in_ebb.
	(get_pseudo_regno): New function.
	(remove_inheritance_pseudos): Add code for undoing pseudo live
	range split and dealing with subregs.  Update debug info too.
	(lra_undo_inheritance): Add code for undoing pseudo live range
	split.  Add printing more debug info.

	* lra-saves.c: Remove.

	* Makefile.in (OBJS): Remove lra-saves.o
	(lra-saves.o): Remove the entry.

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