Index: gcc/builtins.def
===================================================================
--- gcc/builtins.def	(revision 125997)
+++ gcc/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 +609,7 @@ 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_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: gcc/builtins.c
===================================================================
--- gcc/builtins.c	(revision 125997)
+++ gcc/builtins.c	(working copy)
@@ -5513,6 +5513,58 @@ expand_builtin_profile_func (bool exitp)
   return const0_rtx;
 }
 
+/* Expand a call to __builtin___clear_cache.  */
+
+static rtx
+expand_builtin___clear_cache (tree exp ATTRIBUTE_UNUSED)
+{
+#ifndef HAVE_clear_cache
+#ifdef CLEAR_INSN_CACHE
+  /* There is no "clear_cache" insn, and __clear_cache() in libgcc
+     does something.  Just do the default expansion to a call to __clear_cache().  */
+  return NULL_RTX;
+#else
+  /* There is no "clear_cache" insn, and __clear_cache() in libgcc
+     does nothing.  There is no need to call it.  Do nothing.  */
+  return const0_rtx;
+#endif /* CLEAR_INSN_CACHE */
+#else
+  /*  We have a "clear_cache" insn, and it will handle everything.  */
+  tree begin, end;
+  rtx begin_rtx, end_rtx;
+  enum insn_code icode;
+
+  /* We must not expand to a library call.  If we did, any
+     fallback library function in libgcc that might contain a call to
+     __builtin___clear_cache() 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;
+    }
+
+  if (HAVE_clear_cache)
+    {
+      icode = CODE_FOR_clear_cache;
+
+      begin = CALL_EXPR_ARG (exp, 0);
+      begin_rtx = expand_expr (begin, NULL_RTX, Pmode, EXPAND_NORMAL);
+      begin_rtx = convert_memory_address (Pmode, begin_rtx);
+      if (!insn_data[icode].operand[0].predicate (begin_rtx, Pmode))
+	begin_rtx = copy_to_mode_reg (Pmode, begin_rtx);
+
+      end = CALL_EXPR_ARG (exp, 1);
+      end_rtx = expand_expr (end, NULL_RTX, Pmode, EXPAND_NORMAL);
+      end_rtx = convert_memory_address (Pmode, end_rtx);
+      if (!insn_data[icode].operand[1].predicate (end_rtx, Pmode))
+	end_rtx = copy_to_mode_reg (Pmode, end_rtx);
+
+      emit_insn (gen_clear_cache (begin_rtx, end_rtx));
+    }
+  return const0_rtx;
+#endif /* HAVE_clear_cache */
+}
+
 /* Given a trampoline address, make sure it satisfies TRAMPOLINE_ALIGNMENT.  */
 
 static rtx
@@ -6181,6 +6233,12 @@ 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_CLASSIFY_TYPE:
       return expand_builtin_classify_type (exp);
 
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi	(revision 125997)
+++ gcc/doc/extend.texi	(working copy)
@@ -6086,6 +6086,18 @@ 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} 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: gcc/testsuite/gcc.dg/builtins-64.c
===================================================================
--- gcc/testsuite/gcc.dg/builtins-64.c	(revision 0)
+++ gcc/testsuite/gcc.dg/builtins-64.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;
+}