AArch64 - add speculation barrier

Similar to Arm, this adds an unconditional speculation barrier for AArch64.

	* config/aarch64.md (unspecv): Add UNSPECV_SPECULAION_BARRIER.
	(speculation_barrier): New insn.

From-SVN: r263170

gcc/ChangeLog

 2018-07-31  Richard Earnshaw  <rearnsha@arm.com>
 
+	* config/aarch64.md (unspecv): Add UNSPECV_SPECULAION_BARRIER.
+	(speculation_barrier): New insn.
+
+2018-07-31  Richard Earnshaw  <rearnsha@arm.com>
+
 	* config/arm/unspecs.md (unspecv): Add VUNSPEC_SPECULATION_BARRIER.
 	* config/arm/arm.md (speculation_barrier): New expand.
 	(speculation_barrier_insn): New pattern.

gcc/config/aarch64/aarch64.md

@@ -205,6 +205,7 @@
     UNSPECV_SET_FPSR		; Represent assign of FPSR content.
     UNSPECV_BLOCKAGE		; Represent a blockage
     UNSPECV_PROBE_STACK_RANGE	; Represent stack range probing.
+    UNSPECV_SPECULATION_BARRIER ; Represent speculation barrier.
   ]
 )
 
@@ -6554,6 +6555,15 @@
 		   (match_operand 1))
 	      (clobber (reg:CC CC_REGNUM))])])
 
+;; Hard speculation barrier.
+(define_insn "speculation_barrier"
+  [(unspec_volatile [(const_int 0)] UNSPECV_SPECULATION_BARRIER)]
+  ""
+  "isb\;dsb\\tsy"
+  [(set_attr "length" "8")
+   (set_attr "type" "block")]
+)
+
 ;; AdvSIMD Stuff
 (include "aarch64-simd.md")