* [PATCH GCC8][27/33]Extend candidate set if new_cp has cheaper dependence
@ 2017-04-18 10:52 Bin Cheng
2017-04-26 13:38 ` Richard Biener
0 siblings, 1 reply; 2+ messages in thread
From: Bin Cheng @ 2017-04-18 10:52 UTC (permalink / raw)
To: gcc-patches; +Cc: nd
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Hi,
Currently we only allow iv_ca extension if new_cp has cheaper cost and less deps than old_cp.
This is inaccurate because it's possible the overall deps is reduced even new_cp has more deps
than old_cp. This happens in case that new_cp's deps are already in iv_ca. This patch allows
more iv_ca extension by checking overall deps in iv_ca.
Is it OK?
Thanks,
bin
2017-04-11 Bin Cheng <bin.cheng@arm.com>
* tree-ssa-loop-ivopts.c (compare_cost_pair): New.
(iv_ca_more_deps): Renamed to ...
(iv_ca_compare_deps): ... this.
(iv_ca_extend): Extend iv_ca if NEW_CP is cheaper than OLD_CP.
[-- Attachment #2: 0027-extend-cand-with-cheaper-deps-20170310.txt --]
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From 9f45d3762e60b3c1d2de17ef3683f944be408f96 Mon Sep 17 00:00:00 2001
From: Bin Cheng <binche01@e108451-lin.cambridge.arm.com>
Date: Fri, 31 Mar 2017 14:18:55 +0100
Subject: [PATCH 27/33] extend-cand-with-cheaper-deps-20170310.txt
---
gcc/tree-ssa-loop-ivopts.c | 43 ++++++++++++++++++++++++++++++++-----------
1 file changed, 32 insertions(+), 11 deletions(-)
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index b93a589..0b9170c 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -5633,6 +5633,19 @@ cheaper_cost_pair (struct cost_pair *a, struct cost_pair *b)
return false;
}
+/* Compare if A is a more expensive cost pair than B. Return 1, 0 and -1
+ for more expensive, equal and cheaper respectively. */
+
+static int
+compare_cost_pair (struct cost_pair *a, struct cost_pair *b)
+{
+ if (cheaper_cost_pair (a, b))
+ return -1;
+ if (cheaper_cost_pair (b, a))
+ return 1;
+
+ return 0;
+}
/* Returns candidate by that USE is expressed in IVS. */
@@ -5818,13 +5831,14 @@ iv_ca_cost (struct iv_ca *ivs)
return ivs->cost;
}
-/* Returns true if applying NEW_CP to GROUP for IVS introduces more
- invariants than OLD_CP. */
+/* Compare if applying NEW_CP to GROUP for IVS introduces more invariants
+ than OLD_CP. Return 1, 0 and -1 for more, equal and fewer invariants
+ respectively. */
-static bool
-iv_ca_more_deps (struct ivopts_data *data, struct iv_ca *ivs,
- struct iv_group *group, struct cost_pair *old_cp,
- struct cost_pair *new_cp)
+static int
+iv_ca_compare_deps (struct ivopts_data *data, struct iv_ca *ivs,
+ struct iv_group *group, struct cost_pair *old_cp,
+ struct cost_pair *new_cp)
{
gcc_assert (old_cp && new_cp && old_cp != new_cp);
unsigned old_n_invs = ivs->n_invs;
@@ -5832,7 +5846,7 @@ iv_ca_more_deps (struct ivopts_data *data, struct iv_ca *ivs,
unsigned new_n_invs = ivs->n_invs;
iv_ca_set_cp (data, ivs, group, old_cp);
- return (new_n_invs > old_n_invs);
+ return new_n_invs > old_n_invs ? 1 : (new_n_invs < old_n_invs ? -1 : 0);
}
/* Creates change of expressing GROUP by NEW_CP instead of OLD_CP and chains
@@ -6064,11 +6078,18 @@ iv_ca_extend (struct ivopts_data *data, struct iv_ca *ivs,
if (!new_cp)
continue;
- if (!min_ncand && iv_ca_more_deps (data, ivs, group, old_cp, new_cp))
- continue;
+ if (!min_ncand)
+ {
+ int cmp_invs = iv_ca_compare_deps (data, ivs, group, old_cp, new_cp);
+ /* Skip if new_cp depends on more invariants. */
+ if (cmp_invs > 0)
+ continue;
- if (!min_ncand && !cheaper_cost_pair (new_cp, old_cp))
- continue;
+ int cmp_cost = compare_cost_pair (new_cp, old_cp);
+ /* Skip if new_cp is not cheaper. */
+ if (cmp_cost > 0 || (cmp_cost == 0 && cmp_invs == 0))
+ continue;
+ }
*delta = iv_ca_delta_add (group, old_cp, new_cp, *delta);
}
--
1.9.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH GCC8][27/33]Extend candidate set if new_cp has cheaper dependence
2017-04-18 10:52 [PATCH GCC8][27/33]Extend candidate set if new_cp has cheaper dependence Bin Cheng
@ 2017-04-26 13:38 ` Richard Biener
0 siblings, 0 replies; 2+ messages in thread
From: Richard Biener @ 2017-04-26 13:38 UTC (permalink / raw)
To: Bin Cheng; +Cc: gcc-patches, nd
On Tue, Apr 18, 2017 at 12:52 PM, Bin Cheng <Bin.Cheng@arm.com> wrote:
> Hi,
> Currently we only allow iv_ca extension if new_cp has cheaper cost and less deps than old_cp.
> This is inaccurate because it's possible the overall deps is reduced even new_cp has more deps
> than old_cp. This happens in case that new_cp's deps are already in iv_ca. This patch allows
> more iv_ca extension by checking overall deps in iv_ca.
> Is it OK?
Ok.
Richard.
> Thanks,
> bin
> 2017-04-11 Bin Cheng <bin.cheng@arm.com>
>
> * tree-ssa-loop-ivopts.c (compare_cost_pair): New.
> (iv_ca_more_deps): Renamed to ...
> (iv_ca_compare_deps): ... this.
> (iv_ca_extend): Extend iv_ca if NEW_CP is cheaper than OLD_CP.
^ permalink raw reply [flat|nested] 2+ messages in thread
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