[lra] patch mostly implementing pseudo live range split

[Vladimir Makarov <vmakarov at redhat dot com>]

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.

Attachment: nov29.patch
Description: Text document