From: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Cc: Vladimir Makarov <vmakarov@redhat.com>, Jeff Law <law@redhat.com>,
ramrad01@arm.com
Subject: [PATCH 4/8] Disable max_issue when scheduling for register pressure
Date: Tue, 21 Oct 2014 03:31:00 -0000 [thread overview]
Message-ID: <D371E137-568A-4772-B3D7-9A898B0E6B7C@linaro.org> (raw)
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Hi,
This patch disables max_issue-based lookahead multipass scheduling when register-pressure heuristics are active. The two approaches tend to undo each others decisions and don't play well together.
Currently this patch is a no-op, since no target uses both max_issue and register-pressure scheduling. This will change soon with upcoming patches that will enable max_issue during 2nd scheduling pass for ARM and AArch64.
Bootstrapped on x86_64-linux-gnu. Regression testing is in progress. OK to commit if no regressions?
[ChangeLog is part of the git patch]
Thank you,
--
Maxim Kuvyrkov
www.linaro.org
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From caae8fd31b92ea63d91604df4d71a7866303ec2a Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
Date: Tue, 21 Oct 2014 00:25:11 +0100
Subject: [PATCH 4/8] Disable max_issue when scheduling for register pressure
* haifa-sched.c (sched_init): Disable max_issue when scheduling for
register pressure.
---
gcc/haifa-sched.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/gcc/haifa-sched.c b/gcc/haifa-sched.c
index 4f9648c..26d9e29 100644
--- a/gcc/haifa-sched.c
+++ b/gcc/haifa-sched.c
@@ -6867,7 +6867,10 @@ sched_init (void)
else
issue_rate = 1;
- if (targetm.sched.first_cycle_multipass_dfa_lookahead)
+ if (targetm.sched.first_cycle_multipass_dfa_lookahead
+ /* Don't use max_issue with reg_pressure scheduling. Multipass
+ scheduling and reg_pressure scheduling undo each other's decisions. */
+ && sched_pressure == SCHED_PRESSURE_NONE)
dfa_lookahead = targetm.sched.first_cycle_multipass_dfa_lookahead ();
else
dfa_lookahead = 0;
--
1.7.9.5
next reply other threads:[~2014-10-21 3:21 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-21 3:31 Maxim Kuvyrkov [this message]
2014-10-21 15:57 ` Vladimir Makarov
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