From 838e0db2a31fb0872a8b8db68b69f28cde4f4bf4 Mon Sep 17 00:00:00 2001
From: merrill <merrill@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Fri, 3 Mar 1995 03:45:02 +0000
Subject: Update CLEANUP_POINT_EXPR docs.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@9118 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/tree.def | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

(limited to 'gcc/tree.def')

diff --git a/gcc/tree.def b/gcc/tree.def
index 1338a73b65a..453e2886482 100644
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -444,8 +444,20 @@ DEFTREECODE (METHOD_CALL_EXPR, "method_call_expr", "e", 4)
 DEFTREECODE (WITH_CLEANUP_EXPR, "with_cleanup_expr", "e", 3)
 
 /* Specify a cleanup point.
-   Operand 0 is the expression that has cleanups that we want ensure are
-   cleaned up.  */
+   Operand 0 is an expression that may have cleanups.  If it does, those
+   cleanups are executed after the expression is expanded.
+
+   Note that if the expression is a reference to storage, it is forced out
+   of memory before the cleanups are run.  This is necessary to handle
+   cases where the cleanups modify the storage referenced; in the
+   expression 't.i', if 't' is a struct with an integer member 'i' and a
+   cleanup which modifies 'i', the value of the expression depends on
+   whether the cleanup is run before or after 't.i' is evaluated.  When
+   expand_expr is run on 't.i', it returns a MEM.  This is not good enough;
+   the value of 't.i' must be forced out of memory.
+
+   As a consequence, the operand of a CLEANUP_POINT_EXPR must not have
+   BLKmode, because it will not be forced out of memory.  */
 DEFTREECODE (CLEANUP_POINT_EXPR, "cleanup_point_expr", "e", 1)
 
 /* The following two codes are used in languages that have types where
-- 
cgit v1.2.1

