Arm - add speculation_barrier pattern

This patch defines a speculation barrier for AArch32.

	* config/arm/unspecs.md (unspecv): Add VUNSPEC_SPECULATION_BARRIER.
	* config/arm/arm.md (speculation_barrier): New expand.
	(speculation_barrier_insn): New pattern.

From-SVN: r263169

gcc/ChangeLog

@@ -1,3 +1,9 @@
+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.
+
 2018-07-31  Richard Earnshaw  <rearnsha@arm.com>
 
 	* builtin-types.def (BT_FN_PTR_PTR_VAR): New function type.

gcc/config/arm/arm.md

@@ -12012,6 +12012,27 @@
   [(set_attr "length" "4")
    (set_attr "type" "coproc")])
 
+(define_expand "speculation_barrier"
+  [(unspec_volatile [(const_int 0)] VUNSPEC_SPECULATION_BARRIER)]
+  "TARGET_EITHER"
+  "
+    /* Don't emit anything for Thumb1 and suppress the warning from the
+       generic expansion.  */
+    if (!TARGET_32BIT)
+       DONE;
+  "
+)
+
+;; Generate a hard speculation barrier when we have not enabled speculation
+;; tracking.
+(define_insn "*speculation_barrier_insn"
+  [(unspec_volatile [(const_int 0)] VUNSPEC_SPECULATION_BARRIER)]
+  "TARGET_32BIT"
+  "isb\;dsb\\tsy"
+  [(set_attr "type" "block")
+   (set_attr "length" "8")]
+)
+
 ;; Vector bits common to IWMMXT and Neon
 (include "vec-common.md")
 ;; Load the Intel Wireless Multimedia Extension patterns

gcc/config/arm/unspecs.md

@@ -168,6 +168,7 @@
   VUNSPEC_MCRR2		; Represent the coprocessor mcrr2 instruction.
   VUNSPEC_MRRC		; Represent the coprocessor mrrc instruction.
   VUNSPEC_MRRC2		; Represent the coprocessor mrrc2 instruction.
+  VUNSPEC_SPECULATION_BARRIER ; Represents an unconditional speculation barrier.
 ])
 
 ;; Enumerators for NEON unspecs.