[PATCH] dwarf2out: Fix up CONST_WIDE_INT handling once more [PR103046]

[Jakub Jelinek]

On Wed, Nov 03, 2021 at 01:59:27PM +0100, Richard Biener wrote:
> >      case CONST_WIDE_INT:
> > -      {
> > -	wide_int w1 = rtx_mode_t (rtl, MAX_MODE_INT);
> > -	unsigned int prec = MIN (wi::min_precision (w1, UNSIGNED),
> > -				 (unsigned int) CONST_WIDE_INT_NUNITS (rtl)
> > -				 * HOST_BITS_PER_WIDE_INT);
> > -	wide_int w = wide_int::from (w1, prec, UNSIGNED);
> > -	add_AT_wide (die, DW_AT_const_value, w);
> > -      }
> > +      if (is_int_mode (mode, &int_mode)
> > +	  && (GET_MODE_PRECISION (int_mode)
> > +	      & (HOST_BITS_PER_WIDE_INT - 1)) == 0)
> > +	{
> > +	  wide_int w = rtx_mode_t (rtl, int_mode);
> > +	  add_AT_wide (die, DW_AT_const_value, w);
> > +	}
> 
> ... this at least deserves a comment why we return true doing
> nothing when the mode precision isn't a multiple of 64.  The other
> patch simply extended things.

Oops, that is obviously a bug.  For non-integral mode or mode with
precision not a multiple of 64 I meant to punt.  The reason for the latter
is that if precision is something weird like 123 bits, then the printing
code will print the whole 64-bit elt which would be wrong for at least
unsigned numbers with MSB set.  I guess such modes are still very rare to
non-existing.

2021-11-03  Jakub Jelinek  <jakub@redhat.com>

	PR debug/103046
	* dwarf2out.c (add_const_value_attribute): Add MODE argument, use it
	in CONST_WIDE_INT handling.  Adjust recursive calls.
	(add_location_or_const_value_attribute): Pass DECL_MODE (decl) to
	new add_const_value_attribute argument.
	(tree_add_const_value_attribute): Pass TYPE_MODE (type) to new
	add_const_value_attribute argument.

--- gcc/dwarf2out.c.jj	2021-10-08 10:52:47.086531820 +0200
+++ gcc/dwarf2out.c	2021-11-03 14:06:22.750387774 +0100
@@ -3854,7 +3854,7 @@ static void add_AT_location_description
 					 dw_loc_list_ref);
 static void add_data_member_location_attribute (dw_die_ref, tree,
 						struct vlr_context *);
-static bool add_const_value_attribute (dw_die_ref, rtx);
+static bool add_const_value_attribute (dw_die_ref, machine_mode, rtx);
 static void insert_int (HOST_WIDE_INT, unsigned, unsigned char *);
 static void insert_wide_int (const wide_int &, unsigned char *, int);
 static unsigned insert_float (const_rtx, unsigned char *);
@@ -20081,8 +20081,10 @@ insert_float (const_rtx rtl, unsigned ch
    constants do not necessarily get memory "homes".  */
 
 static bool
-add_const_value_attribute (dw_die_ref die, rtx rtl)
+add_const_value_attribute (dw_die_ref die, machine_mode mode, rtx rtl)
 {
+  scalar_mode int_mode;
+
   switch (GET_CODE (rtl))
     {
     case CONST_INT:
@@ -20097,15 +20099,15 @@ add_const_value_attribute (dw_die_ref di
       return true;
 
     case CONST_WIDE_INT:
-      {
-	wide_int w1 = rtx_mode_t (rtl, MAX_MODE_INT);
-	unsigned int prec = MIN (wi::min_precision (w1, UNSIGNED),
-				 (unsigned int) CONST_WIDE_INT_NUNITS (rtl)
-				 * HOST_BITS_PER_WIDE_INT);
-	wide_int w = wide_int::from (w1, prec, UNSIGNED);
-	add_AT_wide (die, DW_AT_const_value, w);
-      }
-      return true;
+      if (is_int_mode (mode, &int_mode)
+	  && (GET_MODE_PRECISION (int_mode)
+	      & (HOST_BITS_PER_WIDE_INT - 1)) == 0)
+	{
+	  wide_int w = rtx_mode_t (rtl, int_mode);
+	  add_AT_wide (die, DW_AT_const_value, w);
+	  return true;
+	}
+      return false;
 
     case CONST_DOUBLE:
       /* Note that a CONST_DOUBLE rtx could represent either an integer or a
@@ -20190,7 +20192,7 @@ add_const_value_attribute (dw_die_ref di
 
     case CONST:
       if (CONSTANT_P (XEXP (rtl, 0)))
-	return add_const_value_attribute (die, XEXP (rtl, 0));
+	return add_const_value_attribute (die, mode, XEXP (rtl, 0));
       /* FALLTHROUGH */
     case SYMBOL_REF:
       if (!const_ok_for_output (rtl))
@@ -20703,7 +20705,7 @@ add_location_or_const_value_attribute (d
 
   rtl = rtl_for_decl_location (decl);
   if (rtl && (CONSTANT_P (rtl) || GET_CODE (rtl) == CONST_STRING)
-      && add_const_value_attribute (die, rtl))
+      && add_const_value_attribute (die, DECL_MODE (decl), rtl))
     return true;
 
   /* See if we have single element location list that is equivalent to
@@ -20724,7 +20726,7 @@ add_location_or_const_value_attribute (d
       if (GET_CODE (rtl) == EXPR_LIST)
 	rtl = XEXP (rtl, 0);
       if ((CONSTANT_P (rtl) || GET_CODE (rtl) == CONST_STRING)
-	  && add_const_value_attribute (die, rtl))
+	  && add_const_value_attribute (die, DECL_MODE (decl), rtl))
 	 return true;
     }
   /* If this decl is from BLOCK_NONLOCALIZED_VARS, we might need its
@@ -20799,7 +20801,7 @@ tree_add_const_value_attribute (dw_die_r
      symbols.  */
   rtl = rtl_for_decl_init (init, type);
   if (rtl && !early_dwarf)
-    return add_const_value_attribute (die, rtl);
+    return add_const_value_attribute (die, TYPE_MODE (type), rtl);
   /* If the host and target are sane, try harder.  */
   if (CHAR_BIT == 8 && BITS_PER_UNIT == 8
       && initializer_constant_valid_p (init, type))


	Jakub