[AArch64] Add missing "pauth" feature to the .arch_extension directive.

Differential Revision: https://reviews.llvm.org/D94970

Author: MarkMurrayARM

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

@@ -2915,6 +2915,7 @@ static const struct Extension {
     {"sve2-bitperm", {AArch64::FeatureSVE2BitPerm}},
     {"ls64", {AArch64::FeatureLS64}},
     {"xs", {AArch64::FeatureXS}},
+    {"pauth", {AArch64::FeaturePAuth}},
     // FIXME: Unsupported extensions
     {"pan", {}},
     {"lor", {}},

llvm/test/MC/AArch64/armv8.3a-pauth.s

@@ -0,0 +1,6 @@
+// RUN: llvm-mc -triple aarch64-none-linux-gnu -show-encoding -mattr=+pauth   < %s | FileCheck %s
+
+paciasp
+
+// CHECK: .text
+// CHECK: paciasp // encoding: [0x3f,0x23,0x03,0xd5]

llvm/test/MC/AArch64/directive-arch_extension.s

@@ -71,3 +71,7 @@ ldapr x0, [x1]
 .arch_extension ls64
 ld64b x0, [x13]
 // CHECK: ld64b x0, [x13]
+
+.arch_extension pauth
+paciasp
+// CHECK: paciasp