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[PATCH][Arm] Only enable fsched-pressure with Ofast
- From: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Kyrylo Tkachov <Kyrylo dot Tkachov at arm dot com>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>
- Date: Wed, 6 Nov 2019 13:57:04 +0000
- Subject: [PATCH][Arm] Only enable fsched-pressure with Ofast
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The current pressure scheduler doesn't appear to correctly track register
pressure and avoid creating unnecessary spills when register pressure is high.
As a result disabling the early scheduler improves integer performance
considerably and reduces codesize as a bonus. Since scheduling floating point
code is generally beneficial (more registers and higher latencies), only enable
the pressure scheduler with -Ofast.
On Cortex-A57 this gives a 0.7% performance gain on SPECINT2006 as well
as a 0.2% codesize reduction.
Bootstrapped on armhf. OK for commit?
ChangeLog:
2019-11-06 Wilco Dijkstra <wdijkstr@arm.com>
* gcc/common/config/arm-common.c (arm_option_optimization_table):
Enable fsched_pressure with Ofast only.
--
diff --git a/gcc/common/config/arm/arm-common.c b/gcc/common/config/arm/arm-common.c
index 41a920f6dc96833e778faa8dbcc19beac483734c..b761d3abd670a144a593c4b410b1e7fbdcb52f56 100644
--- a/gcc/common/config/arm/arm-common.c
+++ b/gcc/common/config/arm/arm-common.c
@@ -38,7 +38,7 @@ static const struct default_options arm_option_optimization_table[] =
{
/* Enable section anchors by default at -O1 or higher. */
{ OPT_LEVELS_1_PLUS, OPT_fsection_anchors, NULL, 1 },
- { OPT_LEVELS_1_PLUS, OPT_fsched_pressure, NULL, 1 },
+ { OPT_LEVELS_FAST, OPT_fsched_pressure, NULL, 1 },
{ OPT_LEVELS_NONE, 0, NULL, 0 }
};