Re: [ping] Fix PR debug/66728

[Mike Stump <mikestump@comcast.net>]

On Nov 4, 2015, at 1:43 AM, Richard Biener <richard.guenther@gmail.com> wrote:
> I think you should limit the effect of this patch to the dwarf2out use
> as the above doesn't make sense to me.

Since dwarf is so special, and since other clients already do something sort of like this anyway, it isn’t unreasonable to make the client be responsible for picking a sensible mode, and asserting if they fail to.  This also transfers the cost of the special case code out to the one client that needs it, and avoids that cost for all the other clients.

The new patch is below for your consideration.

Ok?

> Ideally we'd have an assert that you don't create a rtx_mode_t with
> VOIDmode or BLKmode.

Added.

> Handling the CONST_WIDE_INT in dwarf2out.c the same as we did before
> (with CONST_DOUBLE)
> looks sensible as far of fixing a regression (I assume the diff to the
> dwarf results in essentially the
> same DWARF as what was present before wide-int).

Yes, the dwarf is the same.

Index: dwarf2out.c
===================================================================
--- dwarf2out.c	(revision 229720)
+++ dwarf2out.c	(working copy)
@@ -15593,8 +15593,15 @@
       return true;
 
     case CONST_WIDE_INT:
-      add_AT_wide (die, DW_AT_const_value,
-		   std::make_pair (rtl, GET_MODE (rtl)));
+      {
+	machine_mode mode = GET_MODE (rtl);
+	if (mode == VOIDmode)
+	  mode = mode_for_size (CONST_WIDE_INT_NUNITS (rtl)
+				* HOST_BITS_PER_WIDE_INT,
+				MODE_INT, 0);
+	add_AT_wide (die, DW_AT_const_value,
+		     std::make_pair (rtl, mode));
+      }
       return true;
 
     case CONST_DOUBLE:
Index: rtl.h
===================================================================
--- rtl.h	(revision 229720)
+++ rtl.h	(working copy)
@@ -2086,6 +2086,7 @@
 inline unsigned int
 wi::int_traits <rtx_mode_t>::get_precision (const rtx_mode_t &x)
 {
+  gcc_assert (x.second != BLKmode && x.second != VOIDmode);
   return GET_MODE_PRECISION (x.second);
 }