1 files changed, 77 insertions, 14 deletions

diff --git a/src/cmd/6l/pass.c b/src/cmd/6l/pass.c
index c9b477627..0054b329f 100644
--- a/src/cmd/6l/pass.c
+++ b/src/cmd/6l/pass.c
@@ -79,6 +79,7 @@ nofollow(int a)
 	case ARETFL:
 	case ARETFQ:
 	case ARETFW:
+	case AUNDEF:
 		return 1;
 	}
 	return 0;
@@ -192,20 +193,34 @@ loop:
 		 * recurse to follow one path.
 		 * continue loop on the other.
 		 */
-		q = brchain(p->link);
-		if(q != P && q->mark)
-		if(a != ALOOP) {
-			p->as = relinv(a);
-			p->link = p->pcond;
+		if((q = brchain(p->pcond)) != P)
 			p->pcond = q;
+		if((q = brchain(p->link)) != P)
+			p->link = q;
+		if(p->from.type == D_CONST) {
+			if(p->from.offset == 1) {
+				/*
+				 * expect conditional jump to be taken.
+				 * rewrite so that's the fall-through case.
+				 */
+				p->as = relinv(a);
+				q = p->link;
+				p->link = p->pcond;
+				p->pcond = q;
+			}
+		} else {			
+			q = p->link;
+			if(q->mark)
+			if(a != ALOOP) {
+				p->as = relinv(a);
+				p->link = p->pcond;
+				p->pcond = q;
+			}
 		}
 		xfol(p->link, last);
-		q = brchain(p->pcond);
-		if(q->mark) {
-			p->pcond = q;
+		if(p->pcond->mark)
 			return;
-		}
-		p = q;
+		p = p->pcond;
 		goto loop;
 	}
 	p = p->link;
@@ -295,7 +310,8 @@ patch(void)
 			}
 		}
 		if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd
-		|| HEADTYPE == Hopenbsd || HEADTYPE == Hnetbsd) {
+		|| HEADTYPE == Hopenbsd || HEADTYPE == Hnetbsd
+		|| HEADTYPE == Hplan9x64) {
 			// ELF uses FS instead of GS.
 			if(p->from.type == D_INDIR+D_GS)
 				p->from.type = D_INDIR+D_FS;
@@ -307,7 +323,7 @@ patch(void)
 			if(s) {
 				if(debug['c'])
 					Bprint(&bso, "%s calls %s\n", TNAME, s->name);
-				if((s->type&~SSUB) != STEXT) {
+				if((s->type&SMASK) != STEXT) {
 					/* diag prints TNAME first */
 					diag("undefined: %s", s->name);
 					s->type = STEXT;
@@ -405,7 +421,7 @@ dostkoff(void)
 
 	for(cursym = textp; cursym != nil; cursym = cursym->next) {
 		if(cursym->text == nil || cursym->text->link == nil)
-			continue;
+			continue;				
 
 		p = cursym->text;
 		parsetextconst(p->to.offset);
@@ -413,6 +429,14 @@ dostkoff(void)
 		if(autoffset < 0)
 			autoffset = 0;
 
+		if(autoffset < StackSmall && !(p->from.scale & NOSPLIT)) {
+			for(q = p; q != P; q = q->link)
+				if(q->as == ACALL)
+					goto noleaf;
+			p->from.scale |= NOSPLIT;
+		noleaf:;
+		}
+
 		q = P;
 		if((p->from.scale & NOSPLIT) && autoffset >= StackSmall)
 			diag("nosplit func likely to overflow stack");
@@ -421,7 +445,8 @@ dostkoff(void)
 			p = appendp(p);	// load g into CX
 			p->as = AMOVQ;
 			if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd
-			|| HEADTYPE == Hopenbsd || HEADTYPE == Hnetbsd)	// ELF uses FS
+			|| HEADTYPE == Hopenbsd || HEADTYPE == Hnetbsd
+			|| HEADTYPE == Hplan9x64)	// ELF uses FS
 				p->from.type = D_INDIR+D_FS;
 			else
 				p->from.type = D_INDIR+D_GS;
@@ -579,6 +604,16 @@ dostkoff(void)
 			p->spadj = autoffset;
 			if(q != P)
 				q->pcond = p;
+		} else {
+			// zero-byte stack adjustment.
+			// Insert a fake non-zero adjustment so that stkcheck can
+			// recognize the end of the stack-splitting prolog.
+			p = appendp(p);
+			p->as = ANOP;
+			p->spadj = -PtrSize;
+			p = appendp(p);
+			p->as = ANOP;
+			p->spadj = PtrSize;
 		}
 		deltasp = autoffset;
 
@@ -618,6 +653,34 @@ dostkoff(void)
 			q1->pcond = p;
 		}
 		
+		if(debug['Z'] && autoffset && !(cursym->text->from.scale&NOSPLIT)) {
+			// 6l -Z means zero the stack frame on entry.
+			// This slows down function calls but can help avoid
+			// false positives in garbage collection.
+			p = appendp(p);
+			p->as = AMOVQ;
+			p->from.type = D_SP;
+			p->to.type = D_DI;
+			
+			p = appendp(p);
+			p->as = AMOVQ;
+			p->from.type = D_CONST;
+			p->from.offset = autoffset/8;
+			p->to.type = D_CX;
+			
+			p = appendp(p);
+			p->as = AMOVQ;
+			p->from.type = D_CONST;
+			p->from.offset = 0;
+			p->to.type = D_AX;
+			
+			p = appendp(p);
+			p->as = AREP;
+			
+			p = appendp(p);
+			p->as = ASTOSQ;
+		}
+		
 		for(; p != P; p = p->link) {
 			pcsize = p->mode/8;
 			a = p->from.type;