[Ada] Take into account alignment gap for component reordering

Message ID 1737952.P4YWRSkRpT@polaris
State New
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Series
  • [Ada] Take into account alignment gap for component reordering
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Commit Message

Eric Botcazou Sept. 9, 2017, 12:48 p.m.
This disables the recently implemented component reordering in one more case.

Tested on x86_64-suse-linux, applied on the mainline.


2017-09-09  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/decl.c (components_to_record): Do not reorder in non-
	packed record types if pragma Optimize_Alignment (Space) is enabled.

Patch

Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 251934)
+++ gcc-interface/decl.c	(working copy)
@@ -7683,7 +7683,9 @@  components_to_record (Node_Id gnat_compo
      of a byte, so that they don't cause the regular fields to be either at
      self-referential/variable offset or misaligned.  Note, in the latter
      case, that this can only happen in packed record types so the alignment
-     is effectively capped to the byte for the whole record.
+     is effectively capped to the byte for the whole record.  But we don't
+     do it for non-packed record types if pragma Optimize_Alignment (Space)
+     is specified because this can prevent alignment gaps from being filled.
 
      Optionally, if the layout warning is enabled, keep track of the above 4
      different kinds of fields and issue a warning if some of them would be
@@ -7694,6 +7696,8 @@  components_to_record (Node_Id gnat_compo
   const bool do_reorder
     = (Convention (gnat_record_type) == Convention_Ada
        && !No_Reordering (gnat_record_type)
+       && (!Optimize_Alignment_Space (gnat_record_type)
+	   || Is_Packed (gnat_record_type))
        && !debug__debug_flag_dot_r);
   const bool w_reorder
     = (Convention (gnat_record_type) == Convention_Ada