[PATCH GCC]Improve auto-increment addressing mode support in IVO by refactoring add candiate logic.

["Bin Cheng" <bin dot cheng at arm dot com>]

Hi,
This patch refactors codes adding iv candidates in IVO.  It renames
functions using straightforward names, it also factors function call to
add_autoinc_candidates from add_candidate to add_iv_candidate_for_use.
Before this patch, we tried to add autoinc candidates for every call to
add_candidate.  This has two issues: A) wasting compilation time.  B) adding
useless auto-inc candidates for iv's which have ZERO base.  These autoinc
candidates are useless because targets generally only support auto-increment
addressing mode with base register pointing to memory object, also because
IVO has its prerequisite conditions on autoinc candidates, these cands are
actually ignored later.

I collected instrumental data, and < 85% candidates are added now when
compiling spec2k on Cortex-a15/thumb.

Also this patch could benefit performance for targets supporting autoinc
addressing mode, because with fewer candidates, IVO algorithm might work
better.
I collected spec2k perf data on Cortex-a15.  It shows several cases in
int/fp suites are improved.  Overall, both spec2k geo-mean of int/fp are
both improved by ~0.5%.  And no regression.

Though I haven't turned on autoinc support in IVO for aarch64, I would
expect this patch will pave the way for that.

So is it OK?

Thanks,
bin

2015-07-08  Bin Cheng  <bin.cheng@arm.com>

	* tree-ssa-loop-ivopts.c (add_candidate): Remove call to
	add_autoinc_candidates.
	(add_iv_candidate_for_biv): Rename to add_iv_candidate_for_biv.
	(add_iv_candidate_for_biv): Rename from add_iv_candidate_for_biv.
	(add_old_ivs_candidates): Rename to add_iv_candidate_for_bivs.
	(add_iv_candidate_for_bivs): Rename from add_old_ivs_candidates.
	Call new function.
	(add_iv_value_candidates): Rename to add_iv_candidate_for_use.
	(add_iv_candidate_for_use): Rename from add_iv_value_candidates.
	Remove parameter struct iv*.  Call add_autoinc_candidates here.
	(add_derived_ivs_candidates): Rename to add_iv_candidate_for_uses.
	(add_iv_candidate_for_uses): Rename from add_derived_ivs_candidates.
	Call new function.
	(find_iv_candidates): Call new functions.

Attachment: cleanup-add-candidate-20150707.txt
Description: Text document