[RFC] Return NULL from gimple_call_return_type if no return available.

[Aldy Hernandez via Gcc-patches]

The call to gimple_call_fntype() in gimple_call_return_type() may return
NULL, which causes the TREE_TYPE(lhs) to ICE.  I think it would be best to
return NULL (or void_type_node) rather than aborting.

I'm running into this because fold_using_range::range_of_call, calls
gimple_call_return_type which may ICE for builtins with no LHS.  Instead
of special casing things in range_of_call, perhaps it's best to plug the
source.

Does this sound reasonable?

gcc/ChangeLog:

        * gimple.h (gimple_call_return_type): Return NULL when no type
        and no lhs is available.
---
 gcc/gimple.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gcc/gimple.h b/gcc/gimple.h
index e7dc2a45a13..2a01fe631ec 100644
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -3182,7 +3182,10 @@ gimple_call_return_type (const gcall *gs)
   tree type = gimple_call_fntype (gs);
 
   if (type == NULL_TREE)
-    return TREE_TYPE (gimple_call_lhs (gs));
+    {
+      tree lhs = gimple_call_lhs (gs);
+      return lhs ? TREE_TYPE (lhs) : NULL_TREE;
+    }
 
   /* The type returned by a function is the type of its
      function type.  */
-- 
2.31.1