From 770aaffe0ae52fb9305f9e2b646803ab2c4c0f84 Mon Sep 17 00:00:00 2001
From: Helmut Eller <eller.helmut@gmail.com>
Date: Mon, 24 Jun 2024 10:06:54 +0200
Subject: [PATCH 1/2] Move the Lisp_Fwd.bufoffset field back to the union

* src/lisp.h (struct Lisp_Fwd): With the predicate enum, we can now pack
the offset and the predicate into a one-word struct.
(XBUFFER_OFFSET): Use the new field name.
* src/buffer.c (DEFVAR_PER_BUFFER): Create the one-word struct.
* src/data.c (store_symval_forwarding): Use the new field name.
---
 src/buffer.c | 15 +++++++++------
 src/data.c   |  2 +-
 src/lisp.h   |  9 ++++++---
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/buffer.c b/src/buffer.c
index 39b5e29067a..a69a9a3bbd8 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5017,14 +5017,17 @@ init_buffer (void)
    that nil is allowed too).  DOC is a dummy where you write the doc
    string as a comment.  */
 
-#define DEFVAR_PER_BUFFER(lname, vname, predicate, doc)		\
+#define DEFVAR_PER_BUFFER(lname, vname, predicate_, doc)	\
   do {								\
-    static const struct Lisp_Fwd bo_fwd				\
-	= { .type = Lisp_Fwd_Buffer_Obj,			\
-	    .bufoffset = offsetof (struct buffer, vname##_),	\
-	    .u.bufpredicate = FWDPRED_##predicate };		\
+    static const struct Lisp_Fwd bo_fwd = {			\
+      .type = Lisp_Fwd_Buffer_Obj,				\
+      .u.buf = {						\
+	.offset = offsetof (struct buffer, vname##_),		\
+	.predicate = FWDPRED_##predicate_			\
+      }								\
+    };								\
     static_assert (offsetof (struct buffer, vname##_)		\
-		   < (1 << 8 * sizeof bo_fwd.bufoffset));	\
+		   < (1 << 8 * sizeof bo_fwd.u.buf.offset));	\
     defvar_per_buffer (&bo_fwd, lname);				\
   } while (0)
 
diff --git a/src/data.c b/src/data.c
index 9fd439e07b5..dcf869c1a0e 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1513,7 +1513,7 @@ store_symval_forwarding (lispfwd valcontents, Lisp_Object newval,
       {
 	int offset = XBUFFER_OFFSET (valcontents);
 	if (!NILP (newval))
-	  check_fwd_predicate (valcontents->u.bufpredicate, newval);
+	  check_fwd_predicate (valcontents->u.buf.predicate, newval);
 	if (buf == NULL)
 	  buf = current_buffer;
 	set_per_buffer_value (buf, offset, newval);
diff --git a/src/lisp.h b/src/lisp.h
index e3c2dce7df0..912b208a213 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3180,13 +3180,16 @@ #define INT_TO_INTEGER(expr) \
 struct Lisp_Fwd
 {
   enum Lisp_Fwd_Type type : 8;
-  uint16_t bufoffset;	       /* used if type == Lisp_Fwd_Buffer_Obj */
   union
   {
     intmax_t *intvar;
     bool *boolvar;
     Lisp_Object *objvar;
-    enum Lisp_Fwd_Predicate bufpredicate;
+    struct
+    {
+      uint16_t offset;
+      enum Lisp_Fwd_Predicate predicate : 8;
+    } buf;
     int kbdoffset;
   } u;
 };
@@ -3207,7 +3210,7 @@ BUFFER_OBJFWDP (lispfwd a)
 XBUFFER_OFFSET (lispfwd a)
 {
   eassert (BUFFER_OBJFWDP (a));
-  return a->bufoffset;
+  return a->u.buf.offset;
 }
 
 INLINE bool
-- 
2.39.2