Re: [PATCH] Add DW_AT_const_value as unsigned or int depending on type and value used.

[Mark Wielaard <mjw at redhat dot com>]

On Sun, 2014-03-23 at 12:17 +0100, Mark Wielaard wrote:
> As the comment in the code already indicated DWARF2 does provide
> DW_FORM_sdata/DW_FORM_udata to represent signed/unsigned data.
> Enumeration constants wider than HOST_WIDE_INT are already handled
> separately. Those constant values that do fit a HOST_WIDE_INT can
> be encoded as signed or unsigned depending on type and value for
> more efficient encoding.
>
>    * dwarf2out.c (gen_enumeration_type_die): Add DW_AT_const_value
>    as unsigned or int depending on type and value used.

Since stage 1 opened up I would like to request approval again to push
this. Patch rebased to current master attached.

Thanks,

Mark

commit b81dcfbb049d4cce712ad185c62e503ea9f4658e
Author: Mark Wielaard <mjw@redhat.com>
Date:   Fri Mar 7 22:27:15 2014 +0100

    Add DW_AT_const_value as unsigned or int depending on type and value used.
    
    As the comment in the code already indicated DWARF2 does provide
    DW_FORM_sdata/DW_FORM_udata to represent signed/unsigned data.
    Enumeration constants wider than HOST_WIDE_INT are already handled
    separately. Those constant values that do fit a HOST_WIDE_INT can
    be encoded as signed or unsigned depending on type and value for
    more efficient encoding.
    
    	* dwarf2out.c (gen_enumeration_type_die): Add DW_AT_const_value
    	as unsigned or int depending on type and value used.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b1706ce..355ba29 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2014-03-21  Mark Wielaard  <mjw@redhat.com>
+
+	* dwarf2out.c (gen_enumeration_type_die): Add DW_AT_const_value
+	as unsigned or int depending on type and value used.
+
 2014-03-20  Mark Wielaard  <mjw@redhat.com>
 
 	* dwarf2out.c (add_bound_info): If HOST_WIDE_INT is big enough,
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 7eef56c..d4e4b17 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -17369,19 +17369,14 @@ gen_enumeration_type_die (tree type, dw_die_ref context_die)
 
 	  if (simple_type_size_in_bits (TREE_TYPE (value))
 	      <= HOST_BITS_PER_WIDE_INT || tree_fits_shwi_p (value))
-	    /* DWARF2 does not provide a way of indicating whether or
-	       not enumeration constants are signed or unsigned.  GDB
-	       always assumes the values are signed, so we output all
-	       values as if they were signed.  That means that
-	       enumeration constants with very large unsigned values
-	       will appear to have negative values in the debugger.
-
-	       TODO: the above comment is wrong, DWARF2 does provide
-	       DW_FORM_sdata/DW_FORM_udata to represent signed/unsigned data.
-	       This should be re-worked to use correct signed/unsigned
-	       int/double tags for all cases, instead of always treating as
-	       signed.  */
-	    add_AT_int (enum_die, DW_AT_const_value, TREE_INT_CST_LOW (value));
+	    {
+	      HOST_WIDE_INT val = TREE_INT_CST_LOW (value);
+	      if (TYPE_UNSIGNED (TREE_TYPE (value)) || val >= 0)
+		add_AT_unsigned (enum_die, DW_AT_const_value,
+				 (unsigned HOST_WIDE_INT) val);
+	      else
+		add_AT_int (enum_die, DW_AT_const_value, val);
+	    }
 	  else
 	    /* Enumeration constants may be wider than HOST_WIDE_INT.  Handle
 	       that here.  */