From: Eric Botcazou <ebotcazou@adacore.com>
Date: Wed, 20 May 2020 08:13:05 +0000 (+0200)
Subject: [Ada] Add comment on implementation choice for byte-packed array types
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=5c63fd2c90405ce32a229ebadfea96e46413ec88;p=gcc.git

[Ada] Add comment on implementation choice for byte-packed array types

gcc/ada/

	* freeze.adb (Freeze_Array_Type): Add comment on implementation
	choice for byte-packed array types.
---

diff --git a/gcc/ada/freeze.adb b/gcc/ada/freeze.adb
index cb32f9d3c13..528a7dd8718 100644
--- a/gcc/ada/freeze.adb
+++ b/gcc/ada/freeze.adb
@@ -2928,7 +2928,10 @@ package body Freeze is
 
                      --  Bit packing is not needed for multiples of the storage
                      --  unit if the type is composite because the back end can
-                     --  byte pack composite types.
+                     --  byte pack composite types efficiently. That's not true
+                     --  for discrete types because every read would generate a
+                     --  lot of instructions, so we keep using the manipulation
+                     --  routines of the runtime for them.
 
                      elsif Csiz mod System_Storage_Unit = 0
                        and then Is_Composite_Type (Ctyp)