[gcc r12-4315] [Ada] Fix incorrect size for pathological pass-by-copy parameters

[gcc r12-4315] [Ada] Fix incorrect size for pathological pass-by-copy parameters

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:92961bdf2dfc63965a05302aac6c907065bd2c27

commit r12-4315-g92961bdf2dfc63965a05302aac6c907065bd2c27
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Mon Sep 27 22:44:59 2021 +0200

    [Ada] Fix incorrect size for pathological pass-by-copy parameters
    
    gcc/ada/
    
            * gcc-interface/decl.c (gnat_to_gnu_param): Strip padding types
            only if the size does not change in the process.  Rename local
            variable and add bypass for initialization procedures.

Diff:
---
 gcc/ada/gcc-interface/decl.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/gcc/ada/gcc-interface/decl.c b/gcc/ada/gcc-interface/decl.c
index 13e9004c89d..5e42dd92dc7 100644
--- a/gcc/ada/gcc-interface/decl.c
+++ b/gcc/ada/gcc-interface/decl.c
@@ -5403,19 +5403,21 @@ gnat_to_gnu_param (Entity_Id gnat_param, tree gnu_param_type, bool first,
       mech = Default;
     }
 
-  /* If this is either a foreign function or if the underlying type won't
-     be passed by reference and is as aligned as the original type, strip
-     off possible padding type.  */
+  /* Either for foreign conventions, or if the underlying type is not passed
+     by reference and is as large and aligned as the original type, strip off
+     a possible padding type.  */
   if (TYPE_IS_PADDING_P (gnu_param_type))
     {
-      tree unpadded_type = TREE_TYPE (TYPE_FIELDS (gnu_param_type));
+      tree inner_type = TREE_TYPE (TYPE_FIELDS (gnu_param_type));
 
       if (foreign
 	  || (mech != By_Reference
-	      && !must_pass_by_ref (unpadded_type)
-	      && (mech == By_Copy || !default_pass_by_ref (unpadded_type))
-	      && TYPE_ALIGN (unpadded_type) >= TYPE_ALIGN (gnu_param_type)))
-	gnu_param_type = unpadded_type;
+	      && !must_pass_by_ref (inner_type)
+	      && (mech == By_Copy || !default_pass_by_ref (inner_type))
+	      && ((TYPE_SIZE (inner_type) == TYPE_SIZE (gnu_param_type)
+		   && TYPE_ALIGN (inner_type) >= TYPE_ALIGN (gnu_param_type))
+		  || Is_Init_Proc (gnat_subprog))))
+	gnu_param_type = inner_type;
     }
 
   /* For foreign conventions, pass arrays as pointers to the element type.