Support for -fprolog-pad=Nlinaro/prolog-pad

8 files changed, 74 insertions, 0 deletions

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 9bc02fcf85c..57265c54c97 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -393,6 +393,7 @@ static tree handle_designated_init_attribute (tree *, tree, tree, int, bool *);
 static tree handle_bnd_variable_size_attribute (tree *, tree, tree, int, bool *);
 static tree handle_bnd_legacy (tree *, tree, tree, int, bool *);
 static tree handle_bnd_instrument (tree *, tree, tree, int, bool *);
+static tree handle_prolog_pad_attribute (tree *, tree, tree, int, bool *);
 
 static void check_function_nonnull (tree, int, tree *);
 static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
@@ -833,6 +834,8 @@ const struct attribute_spec c_common_attribute_table[] =
 			      handle_bnd_legacy, false },
   { "bnd_instrument",         0, 0, true, false, false,
 			      handle_bnd_instrument, false },
+  { "prolog_pad",	      1, 1, false, true, true,
+			      handle_prolog_pad_attribute, false },
   { NULL,                     0, 0, false, false, false, NULL, false }
 };
 
@@ -9663,6 +9666,16 @@ handle_designated_init_attribute (tree *node, tree name, tree, int,
   return NULL_TREE;
 }
 
+static tree
+handle_prolog_pad_attribute (tree *, tree name, tree, int,
+			     bool *)
+{
+  warning (OPT_Wattributes,
+	   "%qE attribute is used", name);
+
+  return NULL_TREE;
+}
+
 
 /* Check for valid arguments being passed to a function with FNTYPE.
    There are NARGS arguments in the array ARGARRAY.  */
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 1ce7181c3d4..9d10b1083c2 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -4553,6 +4553,10 @@ will select the smallest suitable mode.
 This section describes the macros that output function entry
 (@dfn{prologue}) and exit (@dfn{epilogue}) code.
 
+@deftypefn {Target Hook} void TARGET_ASM_PRINT_PROLOG_PAD (FILE *@var{file}, unsigned HOST_WIDE_INT @var{pad_size}, bool @var{record_p})
+Generate prologue pad
+@end deftypefn
+
 @deftypefn {Target Hook} void TARGET_ASM_FUNCTION_PROLOGUE (FILE *@var{file}, HOST_WIDE_INT @var{size})
 If defined, a function that outputs the assembler code for entry to a
 function.  The prologue is responsible for setting up the stack frame,
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index a0a0a812fc1..bda6d5c47ce 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -3662,6 +3662,8 @@ will select the smallest suitable mode.
 This section describes the macros that output function entry
 (@dfn{prologue}) and exit (@dfn{epilogue}) code.
 
+@hook TARGET_ASM_PRINT_PROLOG_PAD
+
 @hook TARGET_ASM_FUNCTION_PROLOGUE
 
 @hook TARGET_ASM_FUNCTION_END_PROLOGUE
diff --git a/gcc/final.c b/gcc/final.c
index 1edc446e3f1..862894f59fc 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -1765,6 +1765,22 @@ final_start_function (rtx_insn *first, FILE *file,
 
   high_block_linenum = high_function_linenum = last_linenum;
 
+  tree prolog_pad_attr
+    = lookup_attribute ("prolog_pad", TYPE_ATTRIBUTES (TREE_TYPE (current_function_decl)));
+  if (prolog_pad_attr)
+    {
+      tree prolog_pad_value = TREE_VALUE (TREE_VALUE (prolog_pad_attr));
+      unsigned HOST_WIDE_INT pad_size = 0;
+
+      if (tree_fits_uhwi_p (prolog_pad_value))
+	pad_size = tree_to_uhwi (prolog_pad_value);
+      else
+	gcc_unreachable ();
+
+      if (pad_size > 0)
+	targetm.asm_out.print_prolog_pad (file, pad_size, true);
+    }
+
   if (flag_sanitize & SANITIZE_ADDRESS)
     asan_function_start ();
 
diff --git a/gcc/target.def b/gcc/target.def
index d7543378fe7..63d32854516 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -288,6 +288,12 @@ hidden, protected or internal visibility as specified by @var{visibility}.",
  void, (tree decl, int visibility),
  default_assemble_visibility)
 
+DEFHOOK
+(print_prolog_pad,
+ "Generate prologue pad",
+ void, (FILE *file, unsigned HOST_WIDE_INT pad_size, bool record_p),
+ default_print_prolog_pad)
+
 /* Output the assembler code for entry to a function.  */
 DEFHOOK
 (function_prologue,
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index dcf08631c40..fbe0f40a860 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1499,6 +1499,23 @@ default_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT size,
   return move_by_pieces_ninsns (size, alignment, max_size + 1) < ratio;
 }
 
+void
+default_print_prolog_pad (FILE *file, unsigned HOST_WIDE_INT pad_size,
+			  bool record_p)
+{
+  if (record_p)
+    fprintf (file, "1:");
+  for (int i = 0; i < pad_size; ++i)
+    fprintf (file, "\tnop\n");
+  if (record_p)
+    {
+      fprintf (file, "\t.section __prolog_pads_loc, \"a\",@progbits\n");
+      fprintf (file, "\t.quad 1b\n");
+      fprintf (file, "\t.long %u\n", pad_size);
+      fprintf (file, "\t.previous\n");
+    }
+}
+
 bool
 default_profile_before_prologue (void)
 {
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 47b5cfc3b8b..d03f9930807 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -199,6 +199,7 @@ extern bool default_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT,
 						    enum by_pieces_operation,
 						    bool);
 
+extern void default_print_prolog_pad (FILE *, unsigned HOST_WIDE_INT , bool);
 extern bool default_profile_before_prologue (void);
 extern reg_class_t default_preferred_reload_class (rtx, reg_class_t);
 extern reg_class_t default_preferred_output_reload_class (rtx, reg_class_t);
diff --git a/gcc/testsuite/c-c++-common/attribute-prolog_pad-1.c b/gcc/testsuite/c-c++-common/attribute-prolog_pad-1.c
new file mode 100644
index 00000000000..7404dc546ce
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/attribute-prolog_pad-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+
+void f1(void) __attribute__((prolog_pad(1)));
+void f2(void) __attribute__((prolog_pad(2)));
+
+void
+f1 (void)
+{
+  f2 ();
+}
+
+void f2 (void)
+{
+  f1 ();
+}