Re: [PATCH] Fix PR middle-end/17813

[Eric Botcazou <ebotcazou at libertysurf dot fr>]

> This is the Ada compiler bootstrap failure on i586 and below, which again
> pertains to stack adjustments.  cstand.adb:Create_Standard is miscompiled
> because a stack adjustment is emitted right after a
> __builtin_stack_restore.

Here's the final patch I commited to mainline.  Bootstrapped/regtested (all 
languages except treelang with upcoming patch for PR middle-end/18045) on 
i486-mandrake-linux-gnu, approved offline by Roger.


2004-10-18 ?Eric Botcazou ?<ebotcazou@libertysurf.fr>
              Roger Sayle  <roger@eyesopen.com>

	PR middle-end/17813
	* dojump.c (discard_pending_stack_adjust): New function.
	(clear_pending_stack_adjust): Call it.
	* expr.h (discard_pending_stack_adjust): Declare it.
	* explow.c (emit_stack_save): Emit pending stack adjustments
	before saving the stack pointer.
	(emit_stack_restore): Discard pending stack adjustments before
	restoring the stack pointer.


-- 
Eric Botcazou

Index: dojump.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/dojump.c,v
retrieving revision 1.29
diff -u -p -r1.29 dojump.c
--- dojump.c	8 Sep 2004 07:47:45 -0000	1.29
+++ dojump.c	18 Oct 2004 18:48:23 -0000
@@ -50,6 +50,15 @@ init_pending_stack_adjust (void)
   pending_stack_adjust = 0;
 }
 
+/* Discard any pending stack adjustment.  This avoid relying on the
+   RTL optimizers to remove useless adjustments when we know the
+   stack pointer value is dead.  */
+void discard_pending_stack_adjust (void)
+{
+  stack_pointer_delta -= pending_stack_adjust;
+  pending_stack_adjust = 0;
+}
+
 /* When exiting from function, if safe, clear out any pending stack adjust
    so the adjustment won't get done.
 
@@ -64,10 +73,7 @@ clear_pending_stack_adjust (void)
       && EXIT_IGNORE_STACK
       && ! (DECL_INLINE (current_function_decl) && ! flag_no_inline)
       && ! flag_inline_functions)
-    {
-      stack_pointer_delta -= pending_stack_adjust,
-      pending_stack_adjust = 0;
-    }
+    discard_pending_stack_adjust ();
 }
 
 /* Pop any previously-pushed arguments that have not been popped yet.  */
Index: explow.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/explow.c,v
retrieving revision 1.139
diff -u -p -r1.139 explow.c
--- explow.c	8 Sep 2004 08:05:13 -0000	1.139
+++ explow.c	18 Oct 2004 18:48:33 -0000
@@ -965,6 +965,7 @@ emit_stack_save (enum save_level save_le
       rtx seq;
 
       start_sequence ();
+      do_pending_stack_adjust ();
       /* We must validize inside the sequence, to ensure that any instructions
 	 created by the validize call also get moved to the right place.  */
       if (sa != 0)
@@ -976,6 +977,7 @@ emit_stack_save (enum save_level save_le
     }
   else
     {
+      do_pending_stack_adjust ();
       if (sa != 0)
 	sa = validize_mem (sa);
       emit_insn (fcn (sa, stack_pointer_rtx));
@@ -1032,6 +1034,8 @@ emit_stack_restore (enum save_level save
 		    gen_rtx_MEM (BLKmode, stack_pointer_rtx)));
     }
 
+  discard_pending_stack_adjust ();
+
   if (after)
     {
       rtx seq;
Index: expr.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/expr.h,v
retrieving revision 1.171
diff -u -p -r1.171 expr.h
--- expr.h	8 Sep 2004 18:44:56 -0000	1.171
+++ expr.h	18 Oct 2004 18:48:36 -0000
@@ -499,6 +499,9 @@ extern void expand_var (tree);
    arguments waiting to be popped.  */
 extern void init_pending_stack_adjust (void);
 
+/* Discard any pending stack adjustment.  */
+extern void discard_pending_stack_adjust (void);
+
 /* When exiting from function, if safe, clear out any pending stack adjust
    so the adjustment won't get done.  */
 extern void clear_pending_stack_adjust (void);