Re: [PATCH][Arm] Only enable fsched-pressure with Ofast

[Wilco Dijkstra]

ping

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  <wdijk...@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 }
   };