Index: builtins.def
===================================================================
--- builtins.def	(revision 125997)
+++ builtins.def	(working copy)
@@ -1,6 +1,6 @@
 /* This file contains the definitions and documentation for the
    builtins used in the GNU compiler.
-   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006
+   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
    Free Software Foundation, Inc.
 
 This file is part of GCC.
@@ -609,6 +609,8 @@ DEF_GCC_BUILTIN        (BUILT_IN_APPLY_A
 DEF_GCC_BUILTIN        (BUILT_IN_ARGS_INFO, "args_info", BT_FN_INT_INT, ATTR_NULL)
 DEF_GCC_BUILTIN        (BUILT_IN_BSWAP32, "bswap32", BT_FN_UINT32_UINT32, ATTR_CONST_NOTHROW_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_BSWAP64, "bswap64", BT_FN_UINT64_UINT64, ATTR_CONST_NOTHROW_LIST)
+DEF_EXT_LIB_BUILTIN    (BUILT_IN_CLEAR_CACHE, "__clear_cache", BT_FN_VOID_PTR_PTR, ATTR_NOTHROW_LIST)
+DEF_GCC_BUILTIN        (BUILT_IN_CLEAR_CACHE_INLINE_P, "clear_cache_inline_p", BT_FN_BOOL, ATTR_NOTHROW_LIST)
 DEF_LIB_BUILTIN        (BUILT_IN_CALLOC, "calloc", BT_FN_PTR_SIZE_SIZE, ATTR_MALLOC_NOTHROW_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_CLASSIFY_TYPE, "classify_type", BT_FN_INT_VAR, ATTR_NULL)
 DEF_GCC_BUILTIN        (BUILT_IN_CLZ, "clz", BT_FN_INT_UINT, ATTR_CONST_NOTHROW_LIST)
Index: builtins.c
===================================================================
--- builtins.c	(revision 125997)
+++ builtins.c	(working copy)
@@ -5513,6 +5513,44 @@ expand_builtin_profile_func (bool exitp)
   return const0_rtx;
 }
 
+/* Expand a call to _builtin___clear_cache.  If the target does not
+   support the operation, return NULL_RTX so it expands as a call. */
+static rtx
+expand_builtin_clear_cache (tree exp)
+{
+  tree begin, end;
+  rtx begin_rtx, end_rtx;
+
+  if (!targetm.builtin_clear_cache_inline_p())
+    return NULL_RTX;
+
+  /* We must not expand to a library call if
+     __builtin_clear_cache_inline_p() returns true.  If we did, the
+     fallback library function in libgcc would expand to a call to
+     _builtin___clear_cache() and we would recurse infinitely.  */
+  if (!validate_arglist (exp, POINTER_TYPE, POINTER_TYPE, VOID_TYPE))
+    {
+      error ("both arguments to %<_builtin___clear_cache%> must be pointers");
+      return const0_rtx;
+    }
+
+  begin = CALL_EXPR_ARG (exp, 0);
+  end = CALL_EXPR_ARG (exp, 1);
+
+  /* Evaluate BEGIN and END. */
+  begin_rtx = expand_expr (begin, NULL_RTX, Pmode, EXPAND_NORMAL);
+  begin_rtx = convert_memory_address (Pmode, begin_rtx);
+
+  end_rtx = expand_expr (end, NULL_RTX, Pmode, EXPAND_NORMAL);
+  end_rtx = convert_memory_address (Pmode, end_rtx);
+
+#ifdef HAVE_clear_cache
+  if (HAVE_clear_cache)
+    emit_insn (gen_clear_cache (begin_rtx, end_rtx));
+#endif
+  return const0_rtx;
+}
+
 /* Given a trampoline address, make sure it satisfies TRAMPOLINE_ALIGNMENT.  */
 
 static rtx
@@ -6181,6 +6219,16 @@ expand_builtin (tree exp, rtx target, rt
 	return const0_rtx;
       return expand_builtin_next_arg ();
 
+    case BUILT_IN_CLEAR_CACHE:
+      target = expand_builtin_clear_cache (exp);
+      if (target)
+        return target;
+      break;
+
+    case BUILT_IN_CLEAR_CACHE_INLINE_P:
+      /* This gets folded away.  We should never get here. */
+      gcc_unreachable();
+
     case BUILT_IN_CLASSIFY_TYPE:
       return expand_builtin_classify_type (exp);
 
@@ -9558,6 +9606,14 @@ fold_builtin_unordered_cmp (tree fndecl,
 		      fold_build2 (code, type, arg0, arg1));
 }
 
+/* Fold function call to builtin clear_cache_inline_p. */
+static tree
+fold_builtin_clear_cache_inline_p (tree type)
+{
+  int v = targetm.builtin_clear_cache_inline_p() ? 1 : 0;
+  return constant_boolean_node (v, type);
+}
+
 /* Fold a call to built-in function FNDECL with 0 arguments.
    IGNORE is true if the result of the function call is ignored.  This
    function returns NULL_TREE if no simplification was possible.  */
@@ -9581,6 +9637,9 @@ fold_builtin_0 (tree fndecl, bool ignore
     case BUILT_IN_CLASSIFY_TYPE:
       return fold_builtin_classify_type (NULL_TREE);
 
+    case BUILT_IN_CLEAR_CACHE_INLINE_P:
+      return fold_builtin_clear_cache_inline_p (type);
+
     default:
       break;
     }
Index: target.h
===================================================================
--- target.h	(revision 125997)
+++ target.h	(working copy)
@@ -855,6 +855,9 @@ struct gcc_target
      bits in the bitmap passed in. */  
   void (*live_on_entry) (bitmap); 
 
+  /* Returns true if __builtin_clear_cache will expand in-line. */
+  bool (*builtin_clear_cache_inline_p) (void);
+
   /* True if unwinding tables should be generated by default.  */
   bool unwind_tables_default;
 
Index: target-def.h
===================================================================
--- target-def.h	(revision 125997)
+++ target-def.h	(working copy)
@@ -649,6 +649,10 @@ Foundation, 51 Franklin Street, Fifth Fl
     TARGET_CXX_ADJUST_CLASS_AT_DEFINITION	\
   }
 
+#ifndef TARGET_BUILTIN_CLEAR_CACHE_INLINE_P
+#define TARGET_BUILTIN_CLEAR_CACHE_INLINE_P hook_bool_void_false
+#endif
+
 /* The whole shebang.  */
 #define TARGET_INITIALIZER			\
 {						\
@@ -731,6 +735,7 @@ Foundation, 51 Franklin Street, Fifth Fl
   TARGET_SECONDARY_RELOAD,			\
   TARGET_CXX,					\
   TARGET_EXTRA_LIVE_ON_ENTRY,                    \
+  TARGET_BUILTIN_CLEAR_CACHE_INLINE_P,		\
   TARGET_UNWIND_TABLES_DEFAULT,			\
   TARGET_HAVE_NAMED_SECTIONS,			\
   TARGET_HAVE_SWITCHABLE_BSS_SECTIONS,		\
Index: doc/extend.texi
===================================================================
--- doc/extend.texi	(revision 125997)
+++ doc/extend.texi	(working copy)
@@ -6086,6 +6086,23 @@ if (__builtin_expect (ptr != NULL, 1))
 when testing pointer or floating-point values.
 @end deftypefn
 
+@deftypefn {Built-in Function} void __builtin___clear_cache (char *@var{begin}, char *@var{end})
+This functions is used to flush the processor's instruction cache for
+the region of memory between @var{begin} and @var{end}.  Some
+targets require that the instruction cache be flushed, after modifying
+memory containing code, in order to obtain deterministic behavior.
+
+If the target does not require instruction cache flushes,
+@code{__builtin___clear_cache} has no effect.  Otherwise either
+instructions are emitted in-line to clear the instruction cache or a
+call to the @code{__clear_cache} function in libgcc is made.
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_clear_cache_inline_p (void)
+This function returns @code{false} if @code{__builtin___clear_cache}
+will result in a call to the @code{__clear_cache} function in libgcc.
+@end deftypefn
+
 @deftypefn {Built-in Function} void __builtin_prefetch (const void *@var{addr}, ...)
 This function is used to minimize cache-miss latency by moving data into
 a cache before it is accessed.
Index: doc/tm.texi
===================================================================
--- doc/tm.texi	(revision 125997)
+++ doc/tm.texi	(working copy)
@@ -10093,6 +10093,15 @@ to have to make special provisions in @c
 to reserve space for caller-saved target registers.
 @end deftypefn
 
+@deftypefn {Target Hook} bool TARGET_BUILTIN_CLEAR_CACHE_INLINE_P (void)
+This target hook returns @code{true} if the built-in function
+@code{_builtin___clear_cache} (char * @var{begin}, char * @var{end})
+will be expanded in-line.  Otherwise if @code{false} is returned, the
+built-in will expand to a call to the library function
+@code{__clear_cache} (char * @var{begin}, char * @var{end}).  By
+default, the hook returns @code{false}.
+@end deftypefn
+
 @defmac POWI_MAX_MULTS
 If defined, this macro is interpreted as a signed integer C expression
 that specifies the maximum number of floating point multiplications
Index: testsuite/gcc.dg/builtins-64.c
===================================================================
--- testsuite/gcc.dg/builtins-64.c	(revision 0)
+++ testsuite/gcc.dg/builtins-64.c	(revision 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+int f()
+{
+  /* We must fold away __builtin_clear_cache_inline_p. */
+  return __builtin_clear_cache_inline_p();
+}
+
+/* { dg-final { scan-tree-dump-not "__builtin_clear_cache_inline_p" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: testsuite/gcc.dg/builtins-65.c
===================================================================
--- testsuite/gcc.dg/builtins-65.c	(revision 0)
+++ testsuite/gcc.dg/builtins-65.c	(revision 0)
@@ -0,0 +1,8 @@
+/* { dg-do run } */
+
+int main ()
+{
+  char *mem = __builtin_alloca (40);
+  __builtin___clear_cache (mem, mem + 40);
+  return 0;
+}