c++: Completeness of typedef structs [PR 99294]

When we read in a class definition, we use fixup_type_variants to
propagate the now-completed fields of the class's TYPE to other
variants.  Unfortunately that doesn't propagate all of them, and in
this case we had a typedef to an (incomplete) instantiation.  That
typedef ended up with a VOIDmode, which blew up gimple expansion as
the type itself isn't VOID.  Without modules, that information is
propagated in finalize_type_size when laying out the class.  But that
doesn't happen with stream-in -- we already know the layout.  There is
already some overlap between the two functions, now there's a bit
more.  In fixup_type_variants, I pay attention to the TYPE_NAME to
decide whether to override a user's TYPE_ALIGN -- variants of the
main-variant typedef just copy the main-variant.  Other variants
recalculate.  Overaligning is still permitted.

I also added a TYPE_ALIGN_RAW accessor, and fixed a bug in the
alignment streaming I noticed.  I did not refactor TYPE_ALIGN beyond
using the new accessor.  (It could be written as ((1 << align_raw) >>
1), rather than use the conditional.)

	PR c++/99294
	gcc/
	* tree.h (TYPE_ALIGN_RAW): New accessor.
	(TYPE_ALIGN): Use it.
	gcc/cp/
	* class.c (fixup_type_variants): Propagate mode, precision,
	alignment & emptiness.
	* module.cc (trees_out::type_node): Use TYPE_ALIGN_RAW.
	(trees_in::tree_node): Rematerialize alignment here.
	gcc/testsuite/
	* g++.dg/modules/pr99294.h: New.
	* g++.dg/modules/pr99294_a.C: New.
	* g++.dg/modules/pr99294_b.C: New.

1 files changed, 2 insertions, 2 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 0cb5bd9..369a026 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -8714,7 +8714,7 @@ trees_out::type_node (tree type)
       else
 	{
 	  if (TYPE_USER_ALIGN (type))
-	    flags = exact_log2 (TYPE_ALIGN (type));
+	    flags = TYPE_ALIGN_RAW (type);
 	}
 
       if (streaming_p ())
@@ -9510,7 +9510,7 @@ trees_in::tree_node (bool is_use)
 	  }
 	else
 	  {
-	    res = build_aligned_type (res, 1u << flags);
+	    res = build_aligned_type (res, (1u << flags) >> 1);
 	    TYPE_USER_ALIGN (res) = true;
 	  }