[PATCH][ARM] Switch to default sched pressure algorithm

[Wilco Dijkstra <Wilco.Dijkstra@arm.com>]

Currently the Arm backend selects the alternative sched pressure algorithm.
The issue is that this doesn't take register pressure into account, and so
it causes significant additional spilling on Arm where there are only 14
allocatable registers.  SPEC2006 shows significant codesize reduction
with the default pressure algorithm, so switch back to that.  PR77308 shows
~800 fewer instructions.

SPECINT2006 is ~0.6% faster on Cortex-A57 together with the other DImode
patches. Overall SPEC codesize is 1.1% smaller.

Bootstrap & regress OK on arm-none-linux-gnueabihf --with-cpu=cortex-a57

ChangeLog:
2019-07-29  Wilco Dijkstra  <wdijkstr@arm.com>

	* config/arm/arm.c (arm_option_override): Don't override sched
	pressure algorithm.

--

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 81286cadf32f908e045d704128c5e06842e0cc92..628cf02f23fb29392a63d87f561c3ee2fb73a515 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -3575,11 +3575,6 @@ arm_option_override (void)
   if (use_neon_for_64bits == 1)
      prefer_neon_for_64bits = true;
 
-  /* Use the alternative scheduling-pressure algorithm by default.  */
-  maybe_set_param_value (PARAM_SCHED_PRESSURE_ALGORITHM, SCHED_PRESSURE_MODEL,
-			 global_options.x_param_values,
-			 global_options_set.x_param_values);
-
   /* Look through ready list and all of queue for instructions
      relevant for L2 auto-prefetcher.  */
   int param_sched_autopref_queue_depth;