Re: [PATCH][ARM] Fix PR target/69245 Rewrite arm_set_current_function

[Christian Bruel <christian dot bruel at st dot com>]

On 01/26/2016 04:58 PM, Kyrill Tkachov wrote:
> Hi Christian,
>
> On 26/01/16 15:29, Christian Bruel wrote:
> > On 01/25/2016 05:37 PM, Kyrill Tkachov wrote:
> >
> >
> > So this is ok for trunk with the testcase changed as discussed above and using -O2
> > optimisation level and with a couple comment fixes below.
> >
> > Hi Kyrill,
> >
> > I realized afterwards that my implementation had a flaw with the handling of #pragma GCC reset. What happened is that when both old and new TREE_TARGET_OPTION are NULL, we didn't save_restore the globals flags, to save compute time. The
> > problem is that with #pragma GCC reset, we also fall into this situation, and exit without calling target_reeinit :-(
> >
> > Handling this situation doesn't complicate the code much, because I factorized the calls to target_reeinit + restore_target_globals into a new function (save_restore_target_globals). This function is called from the pragma context when
> > resetting the state arm_reset_previous_fndecl to the default, and from arm_set_current_function when setting to a new target. This is only done when there is a change of the target flags, so no extra computing cost.
> >
> > Same testing as with previous patch:
> >      arm-qemu/
> >      arm-qemu//-mfpu=neon-fp-armv8
> >      arm-qemu//-mfpu=neon
> >
> > Still OK ?
> +/* Restore the TREE_TARGET_GLOBALS from previous state, or save it.  */
> +static void
> +save_restore_target_globals (tree new_tree)
> +{
> +  /* If we have a previous state, use it.  */
> +  if (TREE_TARGET_GLOBALS (new_tree))
> +    restore_target_globals (TREE_TARGET_GLOBALS (new_tree));
> +  else if (new_tree == target_option_default_node)
> +    restore_target_globals (&default_target_globals);
> +  else
> +    {
> +      /* Call target_reinit and save the state for TARGET_GLOBALS.  */
> +      TREE_TARGET_GLOBALS (new_tree) = save_target_globals_default_opts ();
> +    }
> +
> +  arm_option_params_internal ();
> +}
>
> Space before the function comment and signature.
what do you mean ?  a new line between the comment and the function 
signature ? I usually mimic what's done in the other arm.c declarations, 
which sometimes have a new line, sometime not. It's not clear to me 
what's mandatory here, even in the other parts of the compiler.

>   Also, you need to document what is the NEW_TREE
> parameter.
>
>    /* Invalidate arm_previous_fndecl.  */
>    void
> -arm_reset_previous_fndecl (void)
> +arm_reset_previous_fndecl (tree new_tree)
>    {
> +  if (new_tree)
> +    save_restore_target_globals (new_tree);
> +
>      arm_previous_fndecl = NULL_TREE;
>    }
>
> I'm a bit wary of complicating this function. Suddenly it doesn't just reset the previous fndecl
> but also restores globals and can save stuff into its argument. It's suddenly not clear what it's
> purpose is.
> I think it would be clearer if you just added save_restore_target_globals to arm_protos.h and called
> it explicitly from arm_pragma_target_parse when appropriate.

sure, like this one attached (sanity checked) ?


> +
> +  /* If nothing to do return. #pragma GCC reset or #pragma GCC pop to
> +     the default have been handled by save_restore_target_globals from
> +     arm_pragma_target_parse.  */
>
> Two spaces between fullstop and "#pragma GCC".

thanks,

Christian

2016-01-20  Christian Bruel  <christian.bruel@st.com>

	PR target/69245
	* config/arm/arm-c.c (arm_pragma_target_parse): Add comments.
	Move arm_reset_previous_fndecl and set_target_option_current_node in
	the conditional part. Call save_restore_target_globals.
	* config/arm/arm.c (arm_set_current_function):
	Refactor to better support #pragma target and attribute mix.
	Call save_restore_target_globals.
	* config/arm/arm-protos.h (save_restore_target_globals): New function.

2016-01-20  Christian Bruel  <christian.bruel@st.com>

	PR target/69245
	* gcc.target/arm/pr69245.c: New test.

Index: gcc/config/arm/arm-c.c
===================================================================
--- gcc/config/arm/arm-c.c	(revision 232831)
+++ gcc/config/arm/arm-c.c	(working copy)
@@ -221,9 +221,6 @@ arm_pragma_target_parse (tree args, tree pop_targe
 	}
     }
 
-  target_option_current_node = cur_tree;
-  arm_reset_previous_fndecl ();
-
   /* Figure out the previous mode.  */
   prev_opt  = TREE_TARGET_OPTION (prev_tree);
   cur_opt   = TREE_TARGET_OPTION (cur_tree);
@@ -259,6 +256,18 @@ arm_pragma_target_parse (tree args, tree pop_targe
       arm_cpu_builtins (parse_in);
 
       cpp_opts->warn_unused_macros = saved_warn_unused_macros;
+
+      /* Make sure that target_reinit is called for next function, since
+	 TREE_TARGET_OPTION might change with the #pragma even if there is
+	 no target attribute attached to the function.  */
+      arm_reset_previous_fndecl ();
+
+      /* If going to the default mode, we restore the initial states.
+	 if cur_tree is a new target, states will be saved/restored on a per
+	 function basis in arm_set_current_function.  */
+      if (cur_tree == target_option_default_node)
+	save_restore_target_globals (cur_tree);
+
     }
 
   return true;
Index: gcc/config/arm/arm-protos.h
===================================================================
--- gcc/config/arm/arm-protos.h	(revision 232831)
+++ gcc/config/arm/arm-protos.h	(working copy)
@@ -332,6 +332,7 @@ extern bool arm_autoinc_modes_ok_p (machine_mode,
 extern void arm_emit_eabi_attribute (const char *, int, int);
 
 extern void arm_reset_previous_fndecl (void);
+extern void save_restore_target_globals (tree);
 
 /* Defined in gcc/common/config/arm-common.c.  */
 extern const char *arm_rewrite_selected_cpu (const char *name);
Index: gcc/config/arm/arm.c
===================================================================
--- gcc/config/arm/arm.c	(revision 232831)
+++ gcc/config/arm/arm.c	(working copy)
@@ -3446,8 +3446,7 @@ arm_option_override (void)
 
   /* Save the initial options in case the user does function specific
      options.  */
-  target_option_default_node = target_option_current_node
-    = build_target_option_node (&global_options);
+  target_option_default_node = build_target_option_node (&global_options);
 
   /* Init initial mode for testing.  */
   thumb_flipper = TARGET_THUMB;
@@ -29746,7 +29745,27 @@ arm_is_constant_pool_ref (rtx x)
 /* Remember the last target of arm_set_current_function.  */
 static GTY(()) tree arm_previous_fndecl;
 
+/* Restore or save the TREE_TARGET_GLOBALS from or to NEW_TREE.  */
+
+void
+save_restore_target_globals (tree new_tree)
+{
+  /* If we have a previous state, use it.  */
+  if (TREE_TARGET_GLOBALS (new_tree))
+    restore_target_globals (TREE_TARGET_GLOBALS (new_tree));
+  else if (new_tree == target_option_default_node)
+    restore_target_globals (&default_target_globals);
+  else
+    {
+      /* Call target_reinit and save the state for TARGET_GLOBALS.  */
+      TREE_TARGET_GLOBALS (new_tree) = save_target_globals_default_opts ();
+    }
+
+  arm_option_params_internal ();
+}
+
 /* Invalidate arm_previous_fndecl.  */
+
 void
 arm_reset_previous_fndecl (void)
 {
@@ -29756,6 +29775,7 @@ arm_reset_previous_fndecl (void)
 /* Establish appropriate back-end context for processing the function
    FNDECL.  The argument might be NULL to indicate processing at top
    level, outside of any function scope.  */
+
 static void
 arm_set_current_function (tree fndecl)
 {
@@ -29768,38 +29788,23 @@ arm_set_current_function (tree fndecl)
 
   tree new_tree = DECL_FUNCTION_SPECIFIC_TARGET (fndecl);
 
-  arm_previous_fndecl = fndecl;
+  /* If current function has no attributes but previous one did,
+     use the default node."  */
+  if (! new_tree && old_tree)
+    new_tree = target_option_default_node;
+
+  /* If nothing to do return.  #pragma GCC reset or #pragma GCC pop to
+     the default have been handled by save_restore_target_globals from
+     arm_pragma_target_parse.  */
   if (old_tree == new_tree)
     return;
 
-  if (new_tree && new_tree != target_option_default_node)
-    {
-      cl_target_option_restore (&global_options,
-				TREE_TARGET_OPTION (new_tree));
+  arm_previous_fndecl = fndecl;
 
-      if (TREE_TARGET_GLOBALS (new_tree))
-	restore_target_globals (TREE_TARGET_GLOBALS (new_tree));
-      else
-	TREE_TARGET_GLOBALS (new_tree)
-	  = save_target_globals_default_opts ();
-    }
+  /* First set the target options.  */
+  cl_target_option_restore (&global_options, TREE_TARGET_OPTION (new_tree));
 
-  else if (old_tree && old_tree != target_option_default_node)
-    {
-      new_tree = target_option_current_node;
-
-      cl_target_option_restore (&global_options,
-				TREE_TARGET_OPTION (new_tree));
-      if (TREE_TARGET_GLOBALS (new_tree))
-	restore_target_globals (TREE_TARGET_GLOBALS (new_tree));
-      else if (new_tree == target_option_default_node)
-	restore_target_globals (&default_target_globals);
-      else
-	TREE_TARGET_GLOBALS (new_tree)
-	  = save_target_globals_default_opts ();
-    }
-
-  arm_option_params_internal ();
+  save_restore_target_globals (new_tree);
 }
 
 /* Implement TARGET_OPTION_PRINT.  */
Index: gcc/testsuite/gcc.target/arm/pr69245.c
===================================================================
--- gcc/testsuite/gcc.target/arm/pr69245.c	(revision 0)
+++ gcc/testsuite/gcc.target/arm/pr69245.c	(working copy)
@@ -0,0 +1,26 @@
+/* PR target/69245 */
+/* Test that pop_options restores the vfp fpu mode.  */
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_neon_ok } */
+/* { dg-require-effective-target arm_fp_ok } */
+/* { dg-options "-O2" } */
+/* { dg-add-options arm_fp } */
+
+#pragma GCC target "fpu=vfp"
+
+#pragma GCC push_options
+#pragma GCC target "fpu=neon-vfpv4"
+int a, c, d;
+float b;
+static int fn1 ()
+{
+  return 0;
+}
+#pragma GCC pop_options
+
+void fn2 ()
+{
+  d = b * c + a;
+}
+
+/* { dg-final { scan-assembler-times "\.fpu vfp" 1 } } */