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[trunk<-vta] Re: [vta,vta4.3,trunk?] defer creation of DECLs for dwarf indirect constants


On Sep 10, 2008, Alexandre Oliva <aoliva@redhat.com> wrote:

> This is another difference detected by -fcompare-debug, that *may*
> cause codegen differences with or without -g.  At the end of
> compilation of a function that requires constants to be placed in
> memory for debug info, we create new decls.  These new decls cause
> decls in subsequent functions to vary depending on whether debug
> information is generated.  Varying decl uids are known to cause
> codegen differences in some cases, although I don't have any such
> testcase.  They were enough to change anonymous temporary D.<number>
> names in dumps generated for -fcompare-debug, though, which was enough
> of a reason for me to fix it.

> The fix, which should also reduce total memory use during compilation,
> was to delay the creation of DECLs for the constants to the end of
> compilation, when we actually need them to emit debug info.  Until
> then, we hold on to the identifier we'd have used for the DECL.

> Ok for trunk?

Ping?

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

	* dwarf2asm.c (dw2_force_const_mem): Defer creation of
	declarations for constants until...
	(dw2_output_indirect_constant_1): ... this point.

Index: gcc/dwarf2asm.c
===================================================================
--- gcc/dwarf2asm.c.orig	2009-03-01 02:16:17.000000000 -0300
+++ gcc/dwarf2asm.c	2009-05-28 04:35:19.000000000 -0300
@@ -809,7 +809,7 @@ dw2_force_const_mem (rtx x, bool is_publ
 {
   splay_tree_node node;
   const char *key;
-  tree decl;
+  tree decl_id;
 
   if (! indirect_pool)
     /* We use strcmp, rather than just comparing pointers, so that the
@@ -821,7 +821,7 @@ dw2_force_const_mem (rtx x, bool is_publ
   key = XSTR (x, 0);
   node = splay_tree_lookup (indirect_pool, (splay_tree_key) key);
   if (node)
-    decl = (tree) node->value;
+    decl_id = (tree) node->value;
   else
     {
       tree id;
@@ -832,13 +832,9 @@ dw2_force_const_mem (rtx x, bool is_publ
 	  char *ref_name = XALLOCAVEC (char, strlen (str) + sizeof "DW.ref.");
 
 	  sprintf (ref_name, "DW.ref.%s", str);
-	  id = get_identifier (ref_name);
-	  decl = build_decl (VAR_DECL, id, ptr_type_node);
-	  DECL_ARTIFICIAL (decl) = 1;
-	  DECL_IGNORED_P (decl) = 1;
-	  TREE_PUBLIC (decl) = 1;
-	  DECL_INITIAL (decl) = decl;
-	  make_decl_one_only (decl);
+	  gcc_assert (!maybe_get_identifier (ref_name));
+	  decl_id = get_identifier (ref_name);
+	  TREE_PUBLIC (decl_id) = 1;
 	}
       else
 	{
@@ -846,12 +842,8 @@ dw2_force_const_mem (rtx x, bool is_publ
 
 	  ASM_GENERATE_INTERNAL_LABEL (label, "LDFCM", dw2_const_labelno);
 	  ++dw2_const_labelno;
-	  id = get_identifier (label);
-	  decl = build_decl (VAR_DECL, id, ptr_type_node);
-	  DECL_ARTIFICIAL (decl) = 1;
-	  DECL_IGNORED_P (decl) = 1;
-	  TREE_STATIC (decl) = 1;
-	  DECL_INITIAL (decl) = decl;
+	  gcc_assert (!maybe_get_identifier (label));
+	  decl_id = get_identifier (label);
 	}
 
       id = maybe_get_identifier (str);
@@ -859,10 +851,10 @@ dw2_force_const_mem (rtx x, bool is_publ
 	TREE_SYMBOL_REFERENCED (id) = 1;
 
       splay_tree_insert (indirect_pool, (splay_tree_key) key,
-			 (splay_tree_value) decl);
+			 (splay_tree_value) decl_id);
     }
 
-  return XEXP (DECL_RTL (decl), 0);
+  return gen_rtx_SYMBOL_REF (Pmode, IDENTIFIER_POINTER (decl_id));
 }
 
 /* A helper function for dw2_output_indirect_constants called through
@@ -874,10 +866,24 @@ dw2_output_indirect_constant_1 (splay_tr
 {
   const char *sym;
   rtx sym_ref;
-  tree decl;
+  tree id, decl;
 
   sym = (const char *) node->key;
-  decl = (tree) node->value;
+  id = (tree) node->value;
+
+  decl = build_decl (VAR_DECL, id, ptr_type_node);
+  DECL_ARTIFICIAL (decl) = 1;
+  DECL_IGNORED_P (decl) = 1;
+  DECL_INITIAL (decl) = decl;
+
+  if (TREE_PUBLIC (id))
+    {
+      TREE_PUBLIC (decl) = 1;
+      make_decl_one_only (decl);
+    }
+  else
+    TREE_STATIC (decl) = 1;
+
   sym_ref = gen_rtx_SYMBOL_REF (Pmode, sym);
   sym = targetm.strip_name_encoding (sym);
   if (TREE_PUBLIC (decl) && USE_LINKONCE_INDIRECT)
-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer

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