[Bug target/110044] [10, 11, 12, 13, 14 Regression] #pragma pack(push, 1) may not force packing, while __attribute__((packed, aligned(1))) works

["iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110044

--- Comment #6 from Iain Sandoe <iains at gcc dot gnu.org> ---
I'm going to test the following (which will take some time since the hardware
is needed for testing releases too).

The test for AGGREGATE_TYPE_P() could actually be changed to
RECORD_OR_UNION_TYPE_P () - since the case that we might have an array is
handled for non-empty structs (but we do need to guard the empty struct case). 
The problem seems to be we were ignoring that the field type could be packed or
that there was a cap on the max alignment.

If it works as expected then I will apply to the open branches (hopefully
before 10.5 is spun).

----

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 5b3b8b52e7e..e1c038da305 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -8209,7 +8209,8 @@ darwin_rs6000_special_round_type_align (tree type,
unsigned int computed,
       type = TREE_TYPE (type);
   } while (AGGREGATE_TYPE_P (type));

-  if (! AGGREGATE_TYPE_P (type) && type != error_mark_node)
+  if (type != error_mark_node && ! AGGREGATE_TYPE_P (type)
+      ! TYPE_PACKED(type) && maximum_field_alignment == 0)
     align = MAX (align, TYPE_ALIGN (type));

   return align;