From: Russ Cox <rsc@golang.org>
Date: Sat, 22 Dec 2012 16:18:04 +0000 (-0500)
Subject: undo CL 6938073 / 1542912cf09d
X-Git-Tag: go1.1rc2~1557
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=e431398e0947c455e1c34fdd7c0571d17a1365d0;p=gostls13.git

undo CL 6938073 / 1542912cf09d

remove zerostack compiler experiment; will do at link time instead

««« original CL description
cmd/gc: add GOEXPERIMENT=zerostack to clear stack on function entry

This is expensive but it might be useful in cases where
people are suffering from false positives during garbage
collection and are willing to trade the CPU time for getting
rid of the false positives.

On the other hand it only eliminates false positives caused
by other function calls, not false positives caused by dead
temporaries stored in the current function call.

The 5g/6g/8g changes were pulled out of the history, from
the last time we needed to do this (to work around a goto bug).
The code in go.h, lex.c, pgen.c is new but tiny.

R=ken2
CC=golang-dev
https://golang.org/cl/6938073
»»»

R=ken2
CC=golang-dev
https://golang.org/cl/7002051
---

diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index 3d1c68f804..f023b269c8 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -174,64 +174,6 @@ newplist(void)
 	return pl;
 }
 
-void
-clearstk(void)
-{
-	Plist *pl;
-	Prog *p, *p1, *p2, *p3;
-	Node dst, end, zero, con;
-
-	if(plast->firstpc->to.offset <= 0)
-		return;
-
-	// reestablish context for inserting code
-	// at beginning of function.
-	pl = plast;
-	p1 = pl->firstpc;
-	p2 = p1->link;
-	pc = mal(sizeof(*pc));
-	clearp(pc);
-	p1->link = pc;
-	
-	// zero stack frame
-
-	// MOVW $4(SP), R1
-	nodreg(&dst, types[tptr], 1);
-	p = gins(AMOVW, N, &dst);
-	p->from.type = D_CONST;
-	p->from.reg = REGSP;
-	p->from.offset = 4;
-
-	// MOVW $n(R1), R2
-	nodreg(&end, types[tptr], 2);
-	p = gins(AMOVW, N, &end);
-	p->from.type = D_CONST;
-	p->from.reg = 1;
-	p->from.offset = p1->to.offset;
-	
-	// MOVW $0, R3
-	nodreg(&zero, types[TUINT32], 3);
-	nodconst(&con, types[TUINT32], 0);
-	gmove(&con, &zero);
-
-	// L:
-	//	MOVW.P R3, 0(R1) +4
-	//	CMP R1, R2
-	//	BNE L
-	p = gins(AMOVW, &zero, &dst);
-	p->to.type = D_OREG;
-	p->to.offset = 4;
-	p->scond |= C_PBIT;
-	p3 = p;
-	p = gins(ACMP, &dst, N);
-	raddr(&end, p);
-	patch(gbranch(ABNE, T, 0), p3);
-
-	// continue with original code.
-	gins(ANOP, N, N)->link = p2;
-	pc = P;
-}	
-
 void
 gused(Node *n)
 {
diff --git a/src/cmd/6g/gsubr.c b/src/cmd/6g/gsubr.c
index cdc5fdae2e..65d5ad786f 100644
--- a/src/cmd/6g/gsubr.c
+++ b/src/cmd/6g/gsubr.c
@@ -172,44 +172,6 @@ newplist(void)
 	return pl;
 }
 
-void
-clearstk(void)
-{
-	Plist *pl;
-	Prog *p1, *p2;
-	Node sp, di, cx, con, ax;
-
-	if((uint32)plast->firstpc->to.offset <= 0)
-		return;
-
-	// reestablish context for inserting code
-	// at beginning of function.
-	pl = plast;
-	p1 = pl->firstpc;
-	p2 = p1->link;
-	pc = mal(sizeof(*pc));
-	clearp(pc);
-	p1->link = pc;
-	
-	// zero stack frame
-	nodreg(&sp, types[tptr], D_SP);
-	nodreg(&di, types[tptr], D_DI);
-	nodreg(&cx, types[TUINT64], D_CX);
-	nodconst(&con, types[TUINT64], (uint32)p1->to.offset / widthptr);
-	gins(ACLD, N, N);
-	gins(AMOVQ, &sp, &di);
-	gins(AMOVQ, &con, &cx);
-	nodconst(&con, types[TUINT64], 0);
-	nodreg(&ax, types[TUINT64], D_AX);
-	gins(AMOVQ, &con, &ax);
-	gins(AREP, N, N);
-	gins(ASTOSQ, N, N);
-
-	// continue with original code.
-	gins(ANOP, N, N)->link = p2;
-	pc = P;
-}	
-
 void
 gused(Node *n)
 {
diff --git a/src/cmd/8g/gsubr.c b/src/cmd/8g/gsubr.c
index 93cea21469..dbea45a201 100644
--- a/src/cmd/8g/gsubr.c
+++ b/src/cmd/8g/gsubr.c
@@ -173,44 +173,6 @@ newplist(void)
 	return pl;
 }
 
-void
-clearstk(void)
-{
-	Plist *pl;
-	Prog *p1, *p2;
-	Node sp, di, cx, con, ax;
-
-	if(plast->firstpc->to.offset <= 0)
-		return;
-
-	// reestablish context for inserting code
-	// at beginning of function.
-	pl = plast;
-	p1 = pl->firstpc;
-	p2 = p1->link;
-	pc = mal(sizeof(*pc));
-	clearp(pc);
-	p1->link = pc;
-	
-	// zero stack frame
-	nodreg(&sp, types[tptr], D_SP);
-	nodreg(&di, types[tptr], D_DI);
-	nodreg(&cx, types[TUINT32], D_CX);
-	nodconst(&con, types[TUINT32], p1->to.offset / widthptr);
-	gins(ACLD, N, N);
-	gins(AMOVL, &sp, &di);
-	gins(AMOVL, &con, &cx);
-	nodconst(&con, types[TUINT32], 0);
-	nodreg(&ax, types[TUINT32], D_AX);
-	gins(AMOVL, &con, &ax);
-	gins(AREP, N, N);
-	gins(ASTOSL, N, N);
-
-	// continue with original code.
-	gins(ANOP, N, N)->link = p2;
-	pc = P;
-}	
-
 void
 gused(Node *n)
 {
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 42319578a8..36bc4b2954 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -937,7 +937,6 @@ EXTERN	int	funcdepth;
 EXTERN	int	typecheckok;
 EXTERN	int	compiling_runtime;
 EXTERN	int	compiling_wrappers;
-EXTERN	int	zerostack_enabled;
 
 EXTERN	int	nointerface;
 EXTERN	int	fieldtrack_enabled;
@@ -1093,7 +1092,6 @@ void	genlist(NodeList *l);
 Node*	sysfunc(char *name);
 void	tempname(Node *n, Type *t);
 Node*	temp(Type*);
-void	clearstk(void);
 
 /*
  *	init.c
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 8d6487dea7..eabeaeb646 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -41,7 +41,6 @@ static struct {
 } exper[] = {
 //	{"rune32", &rune32},
 	{"fieldtrack", &fieldtrack_enabled},
-	{"zerostack", &zerostack_enabled},
 	{nil, nil},
 };
 
diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index e2cad14398..7be254fff1 100644
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -141,9 +141,6 @@ compile(Node *fn)
 	if(0)
 		frame(0);
 
-	if(zerostack_enabled)
-		clearstk();
-
 ret:
 	lineno = lno;
 }