[SPARC] Fix PR target/86806

[Eric Botcazou]

This adds the speculation barrier on SPARC-V9 in the form of membar #Sync.


2018-12-12  Eric Botcazou  <ebotca...@adacore.com>

        PR target/86806
        * config/sparc/sparc.md (unspecv): Add UNSPECV_SPECULATION_BARRIER.
        (speculation_barrier): New instruction for V9.

-- 
Eric Botcazou
Index: config/sparc/sparc.md
===================================================================
--- config/sparc/sparc.md	(revision 267029)
+++ config/sparc/sparc.md	(working copy)
@@ -104,6 +104,9 @@ (define_c_enum "unspec" [
 
 (define_c_enum "unspecv" [
   UNSPECV_BLOCKAGE
+
+  UNSPECV_SPECULATION_BARRIER
+
   UNSPECV_PROBE_STACK_RANGE
 
   UNSPECV_FLUSHW
@@ -7309,6 +7312,14 @@ (define_insn "*frame_blockage<P:mode>"
   ""
   [(set_attr "length" "0")])
 
+;; We use membar #Sync for the speculation barrier on V9.
+
+(define_insn "speculation_barrier"
+  [(unspec_volatile [(const_int 0)] UNSPECV_SPECULATION_BARRIER)]
+  "TARGET_V9"
+  "membar\t64"
+  [(set_attr "type" "multi")])
+
 (define_expand "probe_stack"
   [(set (match_operand 0 "memory_operand" "") (const_int 0))]
   ""