[6/8,V8M,arm-embedded] Handling ARMv8-M Security Extension's cmse_nonsecure_call attribute

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index d1be6eed1ac153903d50160f3b08d325187acf0b..d13bc2d49508863cf5b45a5f447a70fb468a115c 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -98,6 +98,7 @@ 
 #include "tm-constrs.h"
 #include "rtl-iter.h"
 #include "sched-int.h"
+#include "gimplify.h"
 
 /* Forward definitions of types.  */
 typedef struct minipool_node    Mnode;
@@ -168,6 +169,7 @@  static tree arm_handle_isr_attribute (tree *, tree, tree, int, bool *);
 static tree arm_handle_notshared_attribute (tree *, tree, tree, int, bool *);
 #endif
 static tree arm_handle_cmse_nonsecure_entry (tree *, tree, tree, int, bool *);
+static tree arm_handle_cmse_nonsecure_call (tree *, tree, tree, int, bool *);
 static void arm_output_function_epilogue (FILE *, HOST_WIDE_INT);
 static void arm_output_function_prologue (FILE *, HOST_WIDE_INT);
 static int arm_comp_type_attributes (const_tree, const_tree);
@@ -372,6 +374,8 @@  static const struct attribute_spec arm_attribute_table[] =
   /* ARMv8-M Security Extensions support.  */
   { "cmse_nonsecure_entry", 0, 0, true, false, false,
     arm_handle_cmse_nonsecure_entry, false },
+  { "cmse_nonsecure_call", 0, 0, true, false, false,
+    arm_handle_cmse_nonsecure_call, false },
   { NULL,           0, 0, false, false, false, NULL, false }
 };
 
@@ -6463,6 +6467,76 @@  arm_handle_cmse_nonsecure_entry (tree *node, tree name,
   return NULL_TREE;
 }
 
+
+/* Called upon detection of the use of the cmse_nonsecure_call attribute, this
+   function will check whether the attribute is allowed here and will add the
+   attribute to the function type tree or otherwise issue a diagnose.  The
+   reason we check this at declaration time is to only allow the use of the
+   attribute with declartions of function pointers and not function
+   declartions.  */
+
+static tree
+arm_handle_cmse_nonsecure_call (tree *node, tree name,
+				 tree /* args */,
+				 int /* flags */,
+				 bool *no_add_attrs)
+{
+  tree decl = NULL_TREE;
+  tree type, fntype, main_variant;
+
+  if (!use_cmse)
+    {
+      *no_add_attrs = true;
+      return NULL_TREE;
+    }
+
+  if (TREE_CODE (*node) == VAR_DECL || TREE_CODE (*node) == TYPE_DECL)
+    {
+      decl = *node;
+      type = TREE_TYPE (decl);
+    }
+
+  if (!decl
+      || (!(TREE_CODE (type) == POINTER_TYPE
+	    && TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE)
+	  && TREE_CODE (type) != FUNCTION_TYPE))
+    {
+	warning (OPT_Wattributes, "%qE attribute only applies to base type of a "
+		 "function pointer", name);
+	*no_add_attrs = true;
+	return NULL_TREE;
+    }
+
+  /* type is either a function pointer, when the attribute is used on a function
+   * pointer, or a function type when used in a typedef.  */
+  if (TREE_CODE (type) == FUNCTION_TYPE)
+    fntype = type;
+  else
+    fntype = TREE_TYPE (type);
+
+  *no_add_attrs |= cmse_func_args_or_return_in_stack (NULL, name, fntype);
+
+  if (*no_add_attrs)
+    return NULL_TREE;
+
+  /* Prevent tree's being shared among function types with and without
+     cmse_nonsecure_call attribute.  Do however make sure they keep the same
+     main_variant, this is required for correct DIE output.  */
+  main_variant = TYPE_MAIN_VARIANT (fntype);
+  fntype = build_distinct_type_copy (fntype);
+  TYPE_MAIN_VARIANT (fntype) = main_variant;
+  if (TREE_CODE (type) == FUNCTION_TYPE)
+    TREE_TYPE (decl) = fntype;
+  else
+    TREE_TYPE (type) = fntype;
+
+  /* Construct a type attribute and add it to the function type.  */
+  tree attrs = tree_cons (get_identifier ("cmse_nonsecure_call"), NULL_TREE,
+			  TYPE_ATTRIBUTES (fntype));
+  TYPE_ATTRIBUTES (fntype) = attrs;
+  return NULL_TREE;
+}
+
 /* Return 0 if the attributes for two types are incompatible, 1 if they
    are compatible, and 2 if they are nearly compatible (which causes a
    warning to be generated).  */
diff --git a/gcc/testsuite/gcc.target/arm/cmse/cmse-3.c b/gcc/testsuite/gcc.target/arm/cmse/cmse-3.c
index f806951e90256e8286d2d0f9467b51a73a522e2b..0fe6eff45d2884736ba7049ce4ed5b9785b1018d 100644
--- a/gcc/testsuite/gcc.target/arm/cmse/cmse-3.c
+++ b/gcc/testsuite/gcc.target/arm/cmse/cmse-3.c
@@ -36,3 +36,11 @@  norf (struct span2 a) {}
 
 void __attribute__ ((cmse_nonsecure_entry))
 foo2 (long long a, int b, union test_union c) {} /* { dg-error "not available to functions with arguments passed on the stack" } */
+
+typedef void __attribute__ ((cmse_nonsecure_call)) bar2 (long long a, int b, long long c); /* { dg-error "not available to functions with arguments passed on the stack" } */
+
+typedef void __attribute__ ((cmse_nonsecure_call)) baz2 (long long a, int b, struct span c); /* { dg-error "not available to functions with arguments passed on the stack" } */
+
+typedef struct span __attribute__ ((cmse_nonsecure_call)) qux2 (void); /* { dg-error "not available to functions that return value on the stack" } */
+
+typedef void __attribute__ ((cmse_nonsecure_call)) norf2 (int a, ...); /* { dg-error "not available to functions with variable number of arguments" } */
diff --git a/gcc/testsuite/gcc.target/arm/cmse/cmse-4.c b/gcc/testsuite/gcc.target/arm/cmse/cmse-4.c
index ee4121f2e3f49aed4cae7bcc0e70217cbf1bd809..3521dc61f8fb974b43f504e3f634baf27a559b0b 100644
--- a/gcc/testsuite/gcc.target/arm/cmse/cmse-4.c
+++ b/gcc/testsuite/gcc.target/arm/cmse/cmse-4.c
@@ -20,9 +20,16 @@  baz (void)
   return qux ();
 }
 
+void __attribute__ ((cmse_nonsecure_call))
+quux (void) {} /* { dg-warning "attribute only applies to base type of a function pointer" } */
+
+int __attribute__ ((cmse_nonsecure_call)) norf; /* { dg-warning "attribute only applies to base type of a function pointer" } */
+
 /* { dg-final { scan-assembler-times "bxns" 2 } } */
 /* { dg-final { scan-assembler "foo:" } } */
 /* { dg-final { scan-assembler "__acle_se_foo:" } } */
 /* { dg-final { scan-assembler-not "__acle_se_bar:" } } */
 /* { dg-final { scan-assembler "baz:" } } */
 /* { dg-final { scan-assembler "__acle_se_baz:" } } */
+/* { dg-final { scan-assembler-not "__acle_se_quux:" } } */
+/* { dg-final { scan-assembler-not "__acle_se_norf:" } } */