From: Carl Shapiro <cshapiro@google.com>
Date: Mon, 9 Dec 2013 22:45:10 +0000 (-0800)
Subject: cmd/gc, runtime: correct a misnomer regarding dead value maps
X-Git-Tag: go1.3beta1~1292
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=bc9691c465acb1c7bf9df9848c848408e876bb57;p=gostls13.git

cmd/gc, runtime: correct a misnomer regarding dead value maps

The funcdata symbol incorrectly named the dead value map the
dead pointer map.  The dead value map identifies all dead
values, including pointers and non-pointers, in a stack frame.
The purpose of this map is to allow the runtime to poison
locations of dead data to catch lost invariants.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/38670043
---

diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index c2942f1399..87225a4f88 100644
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -159,7 +159,7 @@ compile(Node *fn)
 	// compile time.  At present, the amount of additional RSS is
 	// substantial enough to affect our smallest build machines.
 	if(0)
-		gcdead = makefuncdatasym("gcdead·%d", FUNCDATA_DeadPointerMaps);
+		gcdead = makefuncdatasym("gcdead·%d", FUNCDATA_DeadValueMaps);
 	else
 		gcdead = nil;
 
diff --git a/src/cmd/gc/plive.c b/src/cmd/gc/plive.c
index b58eaf6ed4..25d6e89b98 100644
--- a/src/cmd/gc/plive.c
+++ b/src/cmd/gc/plive.c
@@ -1477,9 +1477,11 @@ liveness(Node *fn, Prog *firstp, Sym *argssym, Sym *livesym, Sym *deadsym)
 	if(0) livenessprintcfg(lv);
 	livenessepilogue(lv);
 
-	// Emit the map data structures
+	// Emit the live pointer map data structures
 	twobitwritesymbol(lv->livepointers, livesym, nil);
 	twobitwritesymbol(lv->argslivepointers, argssym, nil);
+
+	// Optionally emit a dead value map data structure for locals.
 	if(deadsym != nil)
 		twobitwritesymbol(lv->deadvalues, deadsym, nil);
 
diff --git a/src/pkg/runtime/funcdata.h b/src/pkg/runtime/funcdata.h
index 04766b9da2..e20b6ae254 100644
--- a/src/pkg/runtime/funcdata.h
+++ b/src/pkg/runtime/funcdata.h
@@ -12,7 +12,7 @@
 
 #define FUNCDATA_ArgsPointerMaps 2 /* garbage collector blocks */
 #define FUNCDATA_LocalsPointerMaps 3
-#define FUNCDATA_DeadPointerMaps 4
+#define FUNCDATA_DeadValueMaps 4
 
 // To be used in assembly.
 #define ARGSIZE(n) PCDATA $PCDATA_ArgSize, $n