Index: gcc/config/rs6000/rs6000-builtin.def
===================================================================
--- gcc/config/rs6000/rs6000-builtin.def	(revision 256364)
+++ gcc/config/rs6000/rs6000-builtin.def	(working copy)
@@ -638,7 +638,15 @@
 		     | RS6000_BTC_BINARY),				\
 		    CODE_FOR_ ## ICODE)			/* ICODE */
 
+#define BU_P7_MISC_X(ENUM, NAME, ATTR)					\
+  RS6000_BUILTIN_X (MISC_BUILTIN_ ## ENUM,		/* ENUM */	\
+		    "__builtin_" NAME,			/* NAME */	\
+		    RS6000_BTM_POPCNTD,			/* MASK */	\
+		    (RS6000_BTC_ ## ATTR		/* ATTR */	\
+		     | RS6000_BTC_SPECIAL),				\
+		    CODE_FOR_nothing)			/* ICODE */
 
+
 /* Miscellaneous builtins for instructions added in ISA 2.07.  These
    instructions do require the ISA 2.07 vector support, but they aren't vector
    instructions.  */
@@ -2317,6 +2325,11 @@ BU_DFP_MISC_2 (DSCLIQ,		"dscliq",	CONST,	dfp_dscli
 BU_DFP_MISC_2 (DSCRI,		"dscri",	CONST,	dfp_dscri_dd)
 BU_DFP_MISC_2 (DSCRIQ,		"dscriq",	CONST,	dfp_dscri_td)
 
+/* 0 argument void function that we pretend was added in ISA 2.06.
+   It's a special nop recognized by 2018+ firmware for P7 and up,
+   with speculation barrier semantics.  */
+BU_P7_MISC_X (SPEC_BARRIER,	"speculation_barrier",	MISC)
+
 /* 1 argument BCD functions added in ISA 2.06.  */
 BU_P7_MISC_1 (CDTBCD,		"cdtbcd",	CONST,	cdtbcd)
 BU_P7_MISC_1 (CBCDTD,		"cbcdtd",	CONST,	cbcdtd)
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	(revision 256364)
+++ gcc/config/rs6000/rs6000.c	(working copy)
@@ -16792,6 +16792,12 @@ rs6000_expand_builtin (tree exp, rtx target, rtx s
     case RS6000_BUILTIN_CPU_SUPPORTS:
       return cpu_expand_builtin (fcode, exp, target);
 
+    case MISC_BUILTIN_SPEC_BARRIER:
+      {
+	emit_insn (gen_speculation_barrier ());
+	return NULL_RTX;
+      }
+
     case ALTIVEC_BUILTIN_MASK_FOR_LOAD:
     case ALTIVEC_BUILTIN_MASK_FOR_STORE:
       {
@@ -17164,6 +17170,8 @@ rs6000_init_builtins (void)
 
   ftype = build_function_type_list (void_type_node, NULL_TREE);
   def_builtin ("__builtin_cpu_init", ftype, RS6000_BUILTIN_CPU_INIT);
+  def_builtin ("__builtin_speculation_barrier", ftype,
+	       MISC_BUILTIN_SPEC_BARRIER);
 
   ftype = build_function_type_list (bool_int_type_node, const_ptr_type_node,
 				    NULL_TREE);
Index: gcc/config/rs6000/rs6000.md
===================================================================
--- gcc/config/rs6000/rs6000.md	(revision 256364)
+++ gcc/config/rs6000/rs6000.md	(working copy)
@@ -168,6 +168,7 @@
    UNSPECV_MFFS			; Move from FPSCR
    UNSPECV_MTFSF		; Move to FPSCR Fields
    UNSPECV_SPLIT_STACK_RETURN   ; A camouflaged return
+   UNSPECV_SPEC_BARRIER         ; Speculation barrier
   ])
 
 
@@ -12990,6 +12991,11 @@
     return "ori 1,1,0";
   return "ori 2,2,0";
 })
+
+(define_insn "speculation_barrier"
+  [(unspec_volatile:BLK [(const_int 0)] UNSPECV_SPEC_BARRIER)]
+  ""
+  "ori 31,31,0")
 
 ;; Define the subtract-one-and-jump insns, starting with the template
 ;; so loop.c knows what to generate.
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi	(revision 256364)
+++ gcc/doc/extend.texi	(working copy)
@@ -15734,6 +15734,7 @@ unsigned long __builtin_divdeuo (unsigned long, un
 unsigned int cdtbcd (unsigned int);
 unsigned int cbcdtd (unsigned int);
 unsigned int addg6s (unsigned int, unsigned int);
+void __builtin_speculation_barrier ();
 @end smallexample
 
 The @code{__builtin_divde}, @code{__builtin_divdeo},
Index: gcc/testsuite/gcc.target/powerpc/spec-barr-1.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/spec-barr-1.c	(nonexistent)
+++ gcc/testsuite/gcc.target/powerpc/spec-barr-1.c	(working copy)
@@ -0,0 +1,10 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { "-mcpu=power7" } } */
+/* { dg-options "-mcpu=power7" } */
+
+void foo ()
+{
+  __builtin_speculation_barrier ();
+}
+
+/* { dg-final { scan-assembler "ori 31,31,0" } } */
