From 2da5022bcf578545207ecc0ed0a8c7669e7f708f Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Wed, 20 May 2009 14:57:55 -0700
Subject: change representation of interface values.

this is not a user-visible change.

before, all interface values were

	struct Itype {
		Sigt *type;
		Sigi *inter;
		void *method[n];
	}

	struct Iface {
		void *addr;
		Itype *itype;
	}

the itype is basically a vtable, but it's unnecessary
if the static type is interface{ }.
for interface values with static type empty, the
new representation is

	struct Eface {
		void *addr;
		Sigt *type;
	}

this complicates the code somewhat, but
it reduces the number of Itypes that
have to be computed and cached,
it opens up opportunities to avoid function
calls in a few common cases,
and it will make it possible to lay out
interface{} values at compile time,
which i think i'll need for the new reflection.

R=ken
OCL=28701
CL=29121
---
 src/runtime/runtime.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

(limited to 'src/runtime/runtime.c')

diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
index afb9cce172..57e2570905 100644
--- a/src/runtime/runtime.c
+++ b/src/runtime/runtime.c
@@ -363,7 +363,7 @@ static void
 interprint(uint32 s, Iface *a)
 {
 	USED(s);
-	sys·printinter(*a);
+	sys·printiface(*a);
 }
 
 static uint32
@@ -373,6 +373,27 @@ interequal(uint32 s, Iface *a, Iface *b)
 	return ifaceeq(*a, *b);
 }
 
+static uint64
+nilinterhash(uint32 s, Eface *a)
+{
+	USED(s);
+	return efacehash(*a);
+}
+
+static void
+nilinterprint(uint32 s, Eface *a)
+{
+	USED(s);
+	sys·printeface(*a);
+}
+
+static uint32
+nilinterequal(uint32 s, Eface *a, Eface *b)
+{
+	USED(s);
+	return efaceeq(*a, *b);
+}
+
 uint64
 nohash(uint32 s, void *a)
 {
@@ -416,6 +437,7 @@ algarray[] =
 [ANOEQ]	{ nohash, noequal, memprint, memcopy },
 [ASTRING]	{ strhash, strequal, strprint, memcopy },
 [AINTER]		{ interhash, interequal, interprint, memcopy },
+[ANILINTER]	{ nilinterhash, nilinterequal, nilinterprint, memcopy },
 [AFAKE]	{ nohash, noequal, noprint, nocopy },
 };
 
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