[vta,vta4.3] don't require optimization for -fvar-tracking-assignments

[Alexandre Oliva <aoliva at redhat dot com>]

With SSA enabled at -O0, there's no reason to force
-fvar-tracking-assignments off when not optimizing.

It would be possible to adjust var-tracking to just drop debug insns,
if -fvar-tracking-assignments is enabled with -fvar-tracking disabled,
but this would be useless except for testing that vta doesn't cause
codegen changes.

I think it makes more sense to just disable it, unless -fvar-tracking
is also enabled, to avoid accidental overheads, but with
-fcompare-debug, it might make some sense to support this.  Thoughts?

Meanwhile, I'm checking this in.  For 4.3, removing optimize is not an
option, but there were simplifications available that I made in
parallel with this patch.  The two patches follow.

for  gcc/ChangeLog.vta
from  Alexandre Oliva  <aoliva@redhat.com>

	* toplev.c (process_options): Disregard optimize in
	flag_var_tracking_assignments auto-detect.  Warn and disable if
	it's enabled without -fvar-tracking.
	* doc/invoke.texi (-fvar-tracking-assignments): Update.

Index: gcc/toplev.c
===================================================================
--- gcc/toplev.c.orig	2008-09-11 05:31:07.000000000 -0300
+++ gcc/toplev.c	2008-09-11 05:37:01.000000000 -0300
@@ -1863,22 +1863,18 @@ process_options (void)
     flag_var_tracking = optimize >= 1;
 
   if (flag_var_tracking_assignments == AUTODETECT_VALUE)
-    flag_var_tracking_assignments = flag_var_tracking && optimize;
-  else if (flag_var_tracking_assignments)
-    {
-      if (!optimize)
-	{
-	  warning (0, "variable tracking in assignments requested, "
-		   "but useless without optimization");
-	  flag_var_tracking_assignments = 0;
-	}
-    }
+    flag_var_tracking_assignments = flag_var_tracking;
 
   if (flag_var_tracking_assignments_toggle)
     flag_var_tracking_assignments = !flag_var_tracking_assignments
-      && flag_var_tracking && optimize
-      && (debug_info_level < DINFO_LEVEL_NORMAL
-	  || debug_hooks->var_location == do_nothing_debug_hooks.var_location);
+      && flag_var_tracking;
+
+  if (flag_var_tracking_assignments && !flag_var_tracking)
+    {
+      warning (0, "variable tracking in assignments requested, "
+	       "but useless without variable tracking");
+      flag_var_tracking_assignments = 0;
+    }
 
   if (flag_tree_cselim == AUTODETECT_VALUE)
 #ifdef HAVE_conditional_move
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi.orig	2008-09-11 05:31:08.000000000 -0300
+++ gcc/doc/invoke.texi	2008-09-11 05:45:50.000000000 -0300
@@ -5100,8 +5100,8 @@ the debug info format supports it.
 Annotate assignments to user variables early in the compilation and
 attempt to carry the annotations over throughout the compilation all the
 way to the end, in an attempt to improve debug information while
-optimizing.  It is silently disabled if debug information generation,
-optimization or var-tracking are disabled.
+optimizing.  It is verbosely disabled if it's enabled with var-tracking
+disabled.
 
 @item -fvar-tracking-assignments-toggle
 @opindex fvar-tracking-assignments-toggle

for  gcc/ChangeLog.vta
from  Alexandre Oliva  <aoliva@redhat.com>

	* toplev.c (process_options): Disregard implied debug
	generation in flag_var_tracking_assignments auto-detect.  Warn
	and disable if it's enabled without -fvar-tracking or optimization.
	* doc/invoke.texi (-fvar-tracking-assignments): Update.

Index: gcc/toplev.c
===================================================================
--- gcc/toplev.c.orig	2008-09-11 05:39:51.000000000 -0300
+++ gcc/toplev.c	2008-09-11 05:45:10.000000000 -0300
@@ -1,6 +1,6 @@
 /* Top level of GCC compilers (cc1, cc1plus, etc.)
    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
+   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
    Free Software Foundation, Inc.
 
 This file is part of GCC.
@@ -1953,21 +1953,17 @@ process_options (void)
 
   if (flag_var_tracking_assignments == AUTODETECT_VALUE)
     flag_var_tracking_assignments = flag_var_tracking && optimize;
-  else if (flag_var_tracking_assignments)
-    {
-      if (!optimize)
-	{
-	  warning (0, "variable tracking in assignments requested, "
-		   "but useless without optimization");
-	  flag_var_tracking_assignments = 0;
-	}
-    }
 
   if (flag_var_tracking_assignments_toggle)
     flag_var_tracking_assignments = !flag_var_tracking_assignments
-      && flag_var_tracking && optimize
-      && (debug_info_level < DINFO_LEVEL_NORMAL
-	  || debug_hooks->var_location == do_nothing_debug_hooks.var_location);
+      && flag_var_tracking && optimize;
+
+  if (flag_var_tracking_assignments && !(flag_var_tracking || optimize))
+    {
+      warning (0, "variable tracking in assignments requested, "
+	       "but useless without variable tracking or optimization");
+      flag_var_tracking_assignments = 0;
+    }
 
   if (flag_tree_cselim == AUTODETECT_VALUE)
 #ifdef HAVE_conditional_move
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi.orig	2008-09-11 05:39:51.000000000 -0300
+++ gcc/doc/invoke.texi	2008-09-11 05:45:32.000000000 -0300
@@ -5096,8 +5096,8 @@ the debug info format supports it.
 Annotate assignments to user variables early in the compilation and
 attempt to carry the annotations over throughout the compilation all the
 way to the end, in an attempt to improve debug information while
-optimizing.  It is silently disabled if debug information generation,
-optimization or var-tracking are disabled.
+optimizing.  It is verbosely disabled if it's enabled with var-tracking
+or optimization disabled.
 
 @item -fvar-tracking-assignments-toggle
 @opindex fvar-tracking-assignments-toggle

-- 
Alexandre Oliva         http://www.lsd.ic.unicamp.br/~oliva/
Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}
FSFLA Board Member       ÂSÃ Libre! => http://www.fsfla.org/
Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}