[Patch AArch64] Add initial tuning support for Cortex-A55 and Cortex-A75

[Patch AArch64] Add initial tuning support for Cortex-A55 and Cortex-A75

This patch adds support for the ARM Cortex-A75 and
Cortex-A55 processors through the -mcpu/-mtune values cortex-a55 and
cortex-a75, and an ARM DynamIQ big.LITTLE configuration of these two
processors through the -mcpu/-mtune value cortex-a75.cortex-a55

The ARM Cortex-A75 is ARM's latest and highest performance applications
processor. For the initial tuning provided in this patch, I have chosen to
share the tuning structure with its predecessor, the Cortex-A73.

The ARM Cortex-A55 delivers the best combination of power efficiency
and performance in its class. For the initial tuning provided in this patch,
I have chosen to share the tuning structure with its predecessor, the
Cortex-A53.

Both Cortex-A55 and Cortex-A75 support ARMv8-A with the ARM8.1-A and
ARMv8.2-A extensions, along with the cryptography extension, and
the RCPC extensions from ARMv8.3-A. This is reflected in the patch,
-mcpu=cortex-a75 is treated as equivalent to passing -mtune=cortex-a75
-march=armv8.2-a+rcpc .

2017-06-21  James Greenhalgh  <james.greenhalgh@arm.com>

	* config/aarch64/aarch64-cores.def (cortex-a55): New.
	(cortex-a75): Likewise.
	(cortex-a75.cortex-a55): Likewise.
	* config/aarch64/aarch64-tune.md: Regenerate.
	* doc/invoke.texi (-mtune): Document new values for -mtune.

From-SVN: r249441