[Although I filed this as a middle-end bug, it's really a core infra 
bug, not sure who the best reviewer is]

In working on tree streaming in the modules branch, I discovered poor 
tree node size and hierarchy bits.

Here's a fix for the first part of that.  tree.c (tree_code_size) 
returns sizeof (tree_type_non_common) for any tcc_type node. That's 
wasteful, given we have tree_type_common-> 
tree_type_with_lang_specific-> tree_type_non_common available as 
choices.  It's also obscuring defects in (at least) the c++ FE where we 
use tree_type_non_common fields, but claim the node doesn't contain that 
structure.   Ew.

This patch makes tree_code_size ask the lang hook for the size of 
non-core type nodes.  It also fixes the c++ and objc FEs to return a 
size for the nodes it cares about.

I don't (yet) know whether all the core types are tree_type_non_common, 
nor whether the FE's can return smaller sizes than the do with this 
patch.  But at least the control flow is now correct.  during developing 
this patch I added an assert that the lang hook was returning a size at 
least as big as tree_type_non_common, so they couldn't be more broken 
than before the patch.

I intend to continue cleaning this up of course.  It's not clear to me 
whether we should cache these node sizes in an array, and the way it 
goes about checking nodes with nested switches is understandable, but 
possible not the fastest solution. However let's at least get the sizing 
right first.

ok?

nathan
-- 
Nathan Sidwell