[Ada] improve layout of RETURN type made for CICO mechanism

[Ada] improve layout of RETURN type made for CICO mechanism

[Eric Botcazou]

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One year ago the compiler (gigi) was changed to align the RETURN structure
generated for the Copy-In Copy-Out mechanism:
  http://gcc.gnu.org/ml/gcc-patches/2010-04/msg00256.html
This helps to generate better code, especially on 64-bit platforms.  But this 
is not sufficient in some cases, i.e. when there are integer and fixed-point 
types involved.  The attached patch improves the layout of the type.

Tested on i586-suse-linux, applied on the mainline.


2011-04-08  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Procedure>: Set minimum
 	alignment on fields of the RETURN type built for the Copy-In Copy-Out
	mechanism.


-- 
Eric Botcazou

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Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 172166)
+++ gcc-interface/decl.c	(working copy)
@@ -4226,6 +4226,9 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 		  = create_field_decl (gnu_param_name, gnu_param_type,
 				       gnu_return_type, NULL_TREE, NULL_TREE,
 				       0, 0);
+		/* Set a minimum alignment to speed up accesses.  */
+		if (DECL_ALIGN (gnu_field) < TYPE_ALIGN (gnu_return_type))
+		  DECL_ALIGN (gnu_field) = TYPE_ALIGN (gnu_return_type);
 		Sloc_to_locus (Sloc (gnat_param),
 			       &DECL_SOURCE_LOCATION (gnu_field));
 		DECL_CHAIN (gnu_field) = gnu_field_list;

Re: [Ada] improve layout of RETURN type made for CICO mechanism

[Eric Botcazou]

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> 2011-04-08  Eric Botcazou  <ebotcazou@adacore.com>
>
> 	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Procedure>: Set minimum
>  	alignment on fields of the RETURN type built for the Copy-In Copy-Out
> 	mechanism.

This can be counter-productive, as the RETURN type is bigger and might not fit 
in registers anymore.  This is visible on both x86-64 and PowerPC.

Tested on i586-suse-linux, applied on the mainline.


2012-01-27  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Procedure>: Do not set
	an alignment on fields of the RETURN type built for the CICO mechanism.


-- 
Eric Botcazou

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Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 183609)
+++ gcc-interface/decl.c	(working copy)
@@ -4305,7 +4305,9 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 
 		    gnu_return_type = gnu_new_ret_type;
 		    TYPE_NAME (gnu_return_type) = get_identifier ("RETURN");
-		    /* Set a default alignment to speed up accesses.  */
+		    /* Set a default alignment to speed up accesses.  But we
+		       shouldn't increase the size of the structure too much,
+		       lest it doesn't fit in return registers anymore.  */
 		    TYPE_ALIGN (gnu_return_type)
 		      = get_mode_alignment (ptr_mode);
 		  }
@@ -4314,9 +4316,6 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 		  = create_field_decl (gnu_param_name, gnu_param_type,
 				       gnu_return_type, NULL_TREE, NULL_TREE,
 				       0, 0);
-		/* Set a minimum alignment to speed up accesses.  */
-		if (DECL_ALIGN (gnu_field) < TYPE_ALIGN (gnu_return_type))
-		  DECL_ALIGN (gnu_field) = TYPE_ALIGN (gnu_return_type);
 		Sloc_to_locus (Sloc (gnat_param),
 			       &DECL_SOURCE_LOCATION (gnu_field));
 		DECL_CHAIN (gnu_field) = gnu_field_list;