[ARM][AArch64] Cortex-A75 and Cortex-A55 support

This patch introduces support for Cortex-A75 and Cortex-A55, Arm's
latest big.LITTLE A-class cores. They implement the ARMv8.2-A
architecture, including the cryptography and RAS extensions, plus
the optional dot product extension. They also implement the RCpc
AArch64 extension from ARMv8.3-A.

Cortex-A75:
https://developer.arm.com/products/processors/cortex-a/cortex-a75

Cortex-A55:
https://developer.arm.com/products/processors/cortex-a/cortex-a55

Differential Revision: https://reviews.llvm.org/D36667

llvm-svn: 311316
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index 29aad07..3a9f3c7 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -279,9 +279,11 @@
   case CortexA32:
   case CortexA35:
   case CortexA53:
+  case CortexA55:
   case CortexA57:
   case CortexA72:
   case CortexA73:
+  case CortexA75:
   case CortexR4:
   case CortexR4F:
   case CortexR5: