5g, 8g: remove dead code

maxstksize is superfluous and appears to be vestigial. 6g does not use it.

c >= 4 cannot occur; c = w % 4.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/68750043

src/cmd/5g/gg.h

@@ -28,7 +28,6 @@ EXTERN	Node*	panicindex;
 EXTERN	Node*	panicslice;
 EXTERN	Node*	throwreturn;
 extern	long	unmappedzero;
-EXTERN	int	maxstksize;
 
 /*
  * gen.c

src/cmd/5g/ggen.c

@@ -22,11 +22,8 @@ defframe(Prog *ptxt)
 	ptxt->to.offset2 = rnd(curfn->type->argwid, widthptr);
 
 	// fill in final stack size
-	if(stksize > maxstksize)
-		maxstksize = stksize;
-	frame = rnd(maxstksize+maxarg, widthptr);
+	frame = rnd(stksize+maxarg, widthptr);
 	ptxt->to.offset = frame;
-	maxstksize = 0;
 	
 	p = ptxt;
 	if(stkzerosize > 0) {

src/cmd/8g/gg.h

@@ -31,7 +31,6 @@ EXTERN	Node*	panicindex;
 EXTERN	Node*	panicslice;
 EXTERN	Node*	panicdiv;
 EXTERN	Node*	throwreturn;
-EXTERN	int	maxstksize;
 extern	uint32	unmappedzero;
 
 

src/cmd/8g/ggen.c

@@ -21,11 +21,8 @@ defframe(Prog *ptxt)
 	ptxt->to.offset2 = rnd(curfn->type->argwid, widthptr);
 
 	// fill in final stack size
-	if(stksize > maxstksize)
-		maxstksize = stksize;
-	frame = rnd(maxstksize+maxarg, widthptr);
+	frame = rnd(stksize+maxarg, widthptr);
 	ptxt->to.offset = frame;
-	maxstksize = 0;
 	
 	// insert code to contain ambiguously live variables
 	// so that garbage collector only sees initialized values
@@ -137,11 +134,6 @@ clearfat(Node *nl)
 		q--;
 	}
 
-	if(c >= 4) {
-		gconreg(AMOVL, c, D_CX);
-		gins(AREP, N, N);	// repeat
-		gins(ASTOSB, N, N);	// STOB AL,*(DI)+
-	} else
 	while(c > 0) {
 		gins(ASTOSB, N, N);	// STOB AL,*(DI)+
 		c--;