Re: [PATCH] dwarf2out: Use normal constant values in bound_info if possible.

[Mark Wielaard]

Hi,

On Sun, 2014-03-23 at 12:15 +0100, Mark Wielaard wrote:
>       * dwarf2out.c (add_bound_info): If HOST_WIDE_INT is big enough,
>       then represent the bound as normal constant value.

Since stage 1 opened up I would like to request approval again to push
this. Patch rebased to current master attached. Previous discussion
here: http://gcc.gnu.org/ml/gcc-patches/2014-03/msg01192.html

Thanks,

Mark

commit 668472db0186f79c4e50c6e422c5e90f82017b16
Author: Mark Wielaard <m...@redhat.com>
Date:   Thu Mar 20 18:02:36 2014 +0100

    dwarf2out: Use normal constant values in bound_info if possible.
    
        * dwarf2out.c (add_bound_info): If HOST_WIDE_INT is big enough,
        then represent the bound as normal constant value.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f2c127c..b1706ce 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2014-03-20  Mark Wielaard  <m...@redhat.com>
+
+       * dwarf2out.c (add_bound_info): If HOST_WIDE_INT is big enough,
+       then represent the bound as normal constant value.
+
 2014-04-14  Paolo Carlini  <paolo.carl...@oracle.com>
 
        * tree.h (TYPE_IDENTIFIER): Declare.
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 721f761..7eef56c 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -16203,21 +16203,29 @@ add_bound_info (dw_die_ref subrange_die, enum 
dwarf_attribute bound_attr, tree b
            && tree_to_shwi (bound) == dflt)
          ;
 
-       /* Otherwise represent the bound as an unsigned value with the
-          precision of its type.  The precision and signedness of the
-          type will be necessary to re-interpret it unambiguously.  */
-       else if (prec < HOST_BITS_PER_WIDE_INT)
+       /* If HOST_WIDE_INT is big enough then represent the bound as
+          a constant value.  Note that we need to make sure the type
+          is signed or unsigned.  We cannot just add an unsigned
+          constant if the value itself is positive.  Some DWARF
+          consumers will lookup the bounds type and then sign extend
+          any unsigned values found for signed types.  This is only
+          for DW_AT_lower_bound, normally unsigned values
+          (DW_FORM_data[1248]) are assumed to not need
+          sign-extension.  */
+       else if (prec <= HOST_BITS_PER_WIDE_INT
+                || TREE_INT_CST_HIGH (bound) == 0)
          {
-           unsigned HOST_WIDE_INT mask
-             = ((unsigned HOST_WIDE_INT) 1 << prec) - 1;
-           add_AT_unsigned (subrange_die, bound_attr,
-                            TREE_INT_CST_LOW (bound) & mask);
+           if (TYPE_UNSIGNED (TREE_TYPE (bound)))
+             add_AT_unsigned (subrange_die, bound_attr,
+                              TREE_INT_CST_LOW (bound));
+           else
+             add_AT_int (subrange_die, bound_attr, TREE_INT_CST_LOW (bound));
          }
-       else if (prec == HOST_BITS_PER_WIDE_INT
-                || TREE_INT_CST_HIGH (bound) == 0)
-         add_AT_unsigned (subrange_die, bound_attr,
-                          TREE_INT_CST_LOW (bound));
        else
+         /* Otherwise represent the bound as an unsigned value with
+            the precision of its type.  The precision and signedness
+            of the type will be necessary to re-interpret it
+            unambiguously.  */
          add_AT_double (subrange_die, bound_attr, TREE_INT_CST_HIGH (bound),
                         TREE_INT_CST_LOW (bound));
       }