[PATCH 1/5][Arm] Modify default tuning of armv8.1-m.main to use Cortex-M55

[Omar Tahir]

Previously, compiling with -march=armv8.1-m.main would tune for Cortex-M7.
However, the Cortex-M7 only supports up to Armv7e-M. The Cortex-M55 is the
earliest CPU that supports Armv8.1-M Mainline so is more appropriate. This
also has the effect of changing the branch cost function used, which will be
necessary to correctly prioritise conditional instructions over branches in
the rest of this patch series.

Regression tested on arm-none-eabi.


gcc/ChangeLog:

2020-07-30: Omar Tahir <omar.ta...@arm.com>

                * config/arm/arm-cpus.in (armv8.1-m.main): Tune for Cortex-M55.


diff --git a/gcc/config/arm/arm-cpus.in b/gcc/config/arm/arm-cpus.in
index 728be500b80..c98f8ede8fd 100644
--- a/gcc/config/arm/arm-cpus.in
+++ b/gcc/config/arm/arm-cpus.in
@@ -716,7 +716,7 @@ begin arch armv8-r
end arch armv8-r
 begin arch armv8.1-m.main
- tune for cortex-m7
+ tune for cortex-m55
  tune flags CO_PROC
  base 8M_MAIN
  profile M

csel_1.patch
Description: csel_1.patch