[COMMITTED 19/39] ada: VAST: Explain 2-pass algorithm

[Marc Poulhiès]

From: Bob Duff <d...@adacore.com>

Minor: Add a comment.

gcc/ada/ChangeLog:

        * vast.adb (Pass): Add a comment.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/vast.adb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/ada/vast.adb b/gcc/ada/vast.adb
index cd6257ab60c..4a26ddb5b84 100644
--- a/gcc/ada/vast.adb
+++ b/gcc/ada/vast.adb
@@ -145,6 +145,8 @@ package body VAST is
 
    type Pass_Number is range 1 .. 2;
    Pass : Pass_Number;
+   --  We walk the tree twice (with Pass = 1, then Pass = 2), so that we can
+   --  compute information in Pass 1, and then check it in Pass 2.
 
    procedure VAST;
    --  Called by VAST_If_Enabled to do all the checking
-- 
2.53.0