ARM64: Add support for ARM64e pointer authentication codes (PAC).

Contributed by Peter Cawley. #559

src/lj_target_arm64.h

@@ -260,6 +260,9 @@ typedef enum A64Ins {
   A64I_CBZ = 0x34000000,
   A64I_CBNZ = 0x35000000,
 
+  A64I_BRAAZ = 0xd61f081f,
+  A64I_BLRAAZ = 0xd63f081f,
+
   A64I_NOP = 0xd503201f,
 
   /* FP */
@@ -317,6 +320,9 @@ typedef enum A64Ins {
   A64I_FMOV_DI = 0x1e601000,
 } A64Ins;
 
+#define A64I_BR_AUTH	(LJ_ABI_PAUTH ? A64I_BRAAZ : A64I_BR)
+#define A64I_BLR_AUTH	(LJ_ABI_PAUTH ? A64I_BLRAAZ : A64I_BLR)
+
 typedef enum A64Shift {
   A64SH_LSL, A64SH_LSR, A64SH_ASR, A64SH_ROR
 } A64Shift;