cmd/gc: emit explicit type information for local variables

The type information is (and for years has been) included
as an extra field in the address chunk of an instruction.
Unfortunately, suppose there is a string at a+24(FP) and
we have an instruction reading its length. It will say:

        MOVQ x+32(FP), AX

and the type of *that* argument is int (not slice), because
it is the length being read. This confuses the picture seen
by debuggers and now, worse, by the garbage collector.

Instead of attaching the type information to all uses,
emit an explicit list of TYPE instructions with the information.
The TYPE instructions are no-ops whose only role is to
provide an address to attach type information to.

For example, this function:

        func f(x, y, z int) (a, b string) {
                return
        }

now compiles into:

        --- prog list "f" ---
        0000 (/Users/rsc/x.go:3) TEXT    f+0(SB),$0-56
        0001 (/Users/rsc/x.go:3) LOCALS  ,
        0002 (/Users/rsc/x.go:3) TYPE    x+0(FP){int},$8
        0003 (/Users/rsc/x.go:3) TYPE    y+8(FP){int},$8
        0004 (/Users/rsc/x.go:3) TYPE    z+16(FP){int},$8
        0005 (/Users/rsc/x.go:3) TYPE    a+24(FP){string},$16
        0006 (/Users/rsc/x.go:3) TYPE    b+40(FP){string},$16
        0007 (/Users/rsc/x.go:3) MOVQ    $0,b+40(FP)
        0008 (/Users/rsc/x.go:3) MOVQ    $0,b+48(FP)
        0009 (/Users/rsc/x.go:3) MOVQ    $0,a+24(FP)
        0010 (/Users/rsc/x.go:3) MOVQ    $0,a+32(FP)
        0011 (/Users/rsc/x.go:4) RET     ,

The { } show the formerly hidden type information.
The { } syntax is used when printing from within the gc compiler.
It is not accepted by the assemblers.

The same type information is now included on global variables:

0055 (/Users/rsc/x.go:15) GLOBL   slice+0(SB){[]string},$24(AL*0)

This more accurate type information fixes a bug in the
garbage collector's precise heap collection.

The linker only cares about globals right now, but having the
local information should make things a little nicer for Carl
in the future.

Fixes #4907.

R=ken2
CC=golang-dev
https://golang.org/cl/7395056

src/cmd/5g/ggen.c

@@ -28,6 +28,9 @@ void
 markautoused(Prog* p)
 {
 	for (; p; p = p->link) {
+		if (p->as == ATYPE)
+			continue;
+
 		if (p->from.name == D_AUTO && p->from.node)
 			p->from.node->used = 1;
 
@@ -40,12 +43,21 @@ markautoused(Prog* p)
 void
 fixautoused(Prog* p)
 {
-	for (; p; p = p->link) {
+	Prog **lp;
+
+	for (lp=&p; (p=*lp) != P; ) {
+		if (p->as == ATYPE && p->from.node && p->from.name == D_AUTO && !p->from.node->used) {
+			*lp = p->link;
+			continue;
+		}
+
 		if (p->from.name == D_AUTO && p->from.node)
 			p->from.offset += p->from.node->stkdelta;
 
 		if (p->to.name == D_AUTO && p->to.node)
 			p->to.offset += p->to.node->stkdelta;
+
+		lp = &p->link;
 	}
 }
 

src/cmd/5g/gsubr.c

@@ -192,15 +192,16 @@ gjmp(Prog *to)
 }
 
 void
-ggloblnod(Node *nam, int32 width)
+ggloblnod(Node *nam)
 {
 	Prog *p;
 
 	p = gins(AGLOBL, nam, N);
 	p->lineno = nam->lineno;
+	p->from.gotype = ngotype(nam);
 	p->to.sym = S;
 	p->to.type = D_CONST;
-	p->to.offset = width;
+	p->to.offset = nam->type->width;
 	if(nam->readonly)
 		p->reg = RODATA;
 	if(nam->type != T && !haspointers(nam->type))

src/cmd/5g/list.c

@@ -196,7 +196,10 @@ Dconv(Fmt *fp)
 //		goto conv;
 	}
 conv:
-	return fmtstrcpy(fp, str);
+	fmtstrcpy(fp, str);
+	if(a->gotype)
+		fmtprint(fp, "{%s}", a->gotype->name);
+	return 0;
 }
 
 int

src/cmd/5g/peep.c

@@ -76,6 +76,8 @@ peep(void)
 		case AGLOBL:
 		case ANAME:
 		case ASIGNAME:
+		case ALOCALS:
+		case ATYPE:
 			p = p->link;
 		}
 	}

src/cmd/5g/reg.c

@@ -248,6 +248,8 @@ regopt(Prog *firstp)
 		case AGLOBL:
 		case ANAME:
 		case ASIGNAME:
+		case ALOCALS:
+		case ATYPE:
 			continue;
 		}
 		r = rega();

src/cmd/5l/5.out.h

@@ -198,6 +198,7 @@ enum	as
 	
 	AUSEFIELD,
 	ALOCALS,
+	ATYPE,
 
 	ALAST,
 };

src/cmd/5l/obj.c

@@ -578,6 +578,10 @@ loop:
 		pc++;
 		break;
 
+	case ATYPE:
+		pc++;
+		goto loop;
+
 	case ATEXT:
 		if(cursym != nil && cursym->text) {
 			histtoauto();

src/cmd/5l/span.c

@@ -833,6 +833,7 @@ buildop(void)
 		case ALOCALS:
 		case ACASE:
 		case ABCASE:
+		case ATYPE:
 			break;
 		case AADDF:
 			oprange[AADDD] = oprange[r];

src/cmd/6g/ggen.c

@@ -25,6 +25,9 @@ void
 markautoused(Prog* p)
 {
 	for (; p; p = p->link) {
+		if (p->as == ATYPE)
+			continue;
+
 		if (p->from.type == D_AUTO && p->from.node)
 			p->from.node->used = 1;
 
@@ -35,14 +38,22 @@ markautoused(Prog* p)
 
 // Fixup instructions after compactframe has moved all autos around.
 void
-fixautoused(Prog* p)
+fixautoused(Prog *p)
 {
-	for (; p; p = p->link) {
+	Prog **lp;
+
+	for (lp=&p; (p=*lp) != P; ) {
+		if (p->as == ATYPE && p->from.node && p->from.type == D_AUTO && !p->from.node->used) {
+			*lp = p->link;
+			continue;
+		}
 		if (p->from.type == D_AUTO && p->from.node)
 			p->from.offset += p->from.node->stkdelta;
 
 		if (p->to.type == D_AUTO && p->to.node)
 			p->to.offset += p->to.node->stkdelta;
+
+		lp = &p->link;
 	}
 }
 

src/cmd/6g/gsubr.c

@@ -190,15 +190,16 @@ gjmp(Prog *to)
 }
 
 void
-ggloblnod(Node *nam, int32 width)
+ggloblnod(Node *nam)
 {
 	Prog *p;
 
 	p = gins(AGLOBL, nam, N);
 	p->lineno = nam->lineno;
+	p->from.gotype = ngotype(nam);
 	p->to.sym = S;
 	p->to.type = D_CONST;
-	p->to.offset = width;
+	p->to.offset = nam->type->width;
 	if(nam->readonly)
 		p->from.scale = RODATA;
 	if(nam->type != T && !haspointers(nam->type))
@@ -1179,10 +1180,8 @@ naddr(Node *n, Addr *a, int canemitcode)
 
 	case ONAME:
 		a->etype = 0;
-		if(n->type != T) {
+		if(n->type != T)
 			a->etype = simtype[n->type->etype];
-			a->gotype = ngotype(n);
-		}
 		a->offset = n->xoffset;
 		a->sym = n->sym;
 		a->node = n->orig;

src/cmd/6g/list.c

@@ -161,7 +161,10 @@ brk:
 		strcat(str, s);
 	}
 conv:
-	return fmtstrcpy(fp, str);
+	fmtstrcpy(fp, str);
+	if(a->gotype)
+		fmtprint(fp, "{%s}", a->gotype->name);
+	return 0;
 }
 
 static	char*	regstr[] =

src/cmd/6g/peep.c

@@ -132,6 +132,8 @@ peep(void)
 		case AGLOBL:
 		case ANAME:
 		case ASIGNAME:
+		case ALOCALS:
+		case ATYPE:
 			p = p->link;
 		}
 	}

src/cmd/6g/reg.c

@@ -224,6 +224,8 @@ regopt(Prog *firstp)
 		case AGLOBL:
 		case ANAME:
 		case ASIGNAME:
+		case ALOCALS:
+		case ATYPE:
 			continue;
 		}
 		r = rega();

src/cmd/6l/6.out.h

@@ -759,6 +759,7 @@ enum	as
 	
 	AUSEFIELD,
 	ALOCALS,
+	ATYPE,
 
 	ALAST
 };

src/cmd/6l/obj.c

@@ -591,6 +591,10 @@ loop:
 		pc++;
 		goto loop;
 	
+	case ATYPE:
+		pc++;
+		goto loop;
+
 	case ATEXT:
 		s = p->from.sym;
 		if(s->text != nil) {

src/cmd/6l/optab.c

@@ -1318,6 +1318,7 @@ Optab optab[] =
 
 	{ AUSEFIELD,	ynop,	Px, 0,0 },
 	{ ALOCALS },
+	{ ATYPE },
 
 	{ AEND },
 	0

src/cmd/8g/ggen.c

@@ -27,6 +27,9 @@ void
 markautoused(Prog* p)
 {
 	for (; p; p = p->link) {
+		if (p->as == ATYPE)
+			continue;
+
 		if (p->from.type == D_AUTO && p->from.node)
 			p->from.node->used = 1;
 
@@ -39,12 +42,21 @@ markautoused(Prog* p)
 void
 fixautoused(Prog* p)
 {
-	for (; p; p = p->link) {
+	Prog **lp;
+
+	for (lp=&p; (p=*lp) != P; ) {
+		if (p->as == ATYPE && p->from.node && p->from.type == D_AUTO && !p->from.node->used) {
+			*lp = p->link;
+			continue;
+		}
+
 		if (p->from.type == D_AUTO && p->from.node)
 			p->from.offset += p->from.node->stkdelta;
 
 		if (p->to.type == D_AUTO && p->to.node)
 			p->to.offset += p->to.node->stkdelta;
+
+		lp = &p->link;
 	}
 }
 

src/cmd/8g/gsubr.c

@@ -191,15 +191,16 @@ gjmp(Prog *to)
 }
 
 void
-ggloblnod(Node *nam, int32 width)
+ggloblnod(Node *nam)
 {
 	Prog *p;
 
 	p = gins(AGLOBL, nam, N);
 	p->lineno = nam->lineno;
+	p->from.gotype = ngotype(nam);
 	p->to.sym = S;
 	p->to.type = D_CONST;
-	p->to.offset = width;
+	p->to.offset = nam->type->width;
 	if(nam->readonly)
 		p->from.scale = RODATA;
 	if(nam->type != T && !haspointers(nam->type))
@@ -2260,7 +2261,6 @@ naddr(Node *n, Addr *a, int canemitcode)
 			a->etype = simtype[n->type->etype];
 			dowidth(n->type);
 			a->width = n->type->width;
-			a->gotype = ngotype(n);
 		}
 		a->offset = n->xoffset;
 		a->sym = n->sym;

src/cmd/8g/list.c

@@ -158,7 +158,10 @@ brk:
 		strcat(str, s);
 	}
 conv:
-	return fmtstrcpy(fp, str);
+	fmtstrcpy(fp, str);
+	if(a->gotype)
+		fmtprint(fp, "{%s}", a->gotype->name);
+	return 0;
 }
 
 static	char*	regstr[] =

src/cmd/8g/peep.c

@@ -126,6 +126,8 @@ peep(void)
 		case AGLOBL:
 		case ANAME:
 		case ASIGNAME:
+		case ALOCALS:
+		case ATYPE:
 			p = p->link;
 		}
 	}

src/cmd/8g/reg.c

@@ -195,6 +195,8 @@ regopt(Prog *firstp)
 		case AGLOBL:
 		case ANAME:
 		case ASIGNAME:
+		case ALOCALS:
+		case ATYPE:
 			continue;
 		}
 		r = rega();

src/cmd/8l/8.out.h

@@ -569,6 +569,7 @@ enum	as
 	
 	AUSEFIELD,
 	ALOCALS,
+	ATYPE,
 
 	ALAST
 };

src/cmd/8l/obj.c

@@ -600,6 +600,10 @@ loop:
 		pc++;
 		goto loop;
 
+	case ATYPE:
+		pc++;
+		goto loop;
+
 	case ATEXT:
 		s = p->from.sym;
 		if(s->text != nil) {

src/cmd/8l/optab.c

@@ -963,6 +963,7 @@ Optab optab[] =
 
 	{ AUSEFIELD,	ynop,	Px, 0,0 },
 	{ ALOCALS },
+	{ ATYPE },
 
 	0
 };

src/cmd/gc/closure.c

@@ -13,7 +13,7 @@
 void
 closurehdr(Node *ntype)
 {
-	Node *n, *name, *a, *orig;
+	Node *n, *name, *a;
 	NodeList *l;
 
 	n = nod(OCLOSURE, N, N);
@@ -43,11 +43,8 @@ closurehdr(Node *ntype)
 	}
 	for(l=n->rlist; l; l=l->next) {
 		name = l->n->left;
-		if(name) {
-			orig = name->orig;  // preserve the meaning of orig == N (anonymous PPARAMOUT)
+		if(name)
 			name = newname(name->sym);
-			name->orig = orig;
-		}
 		ntype->rlist = list(ntype->rlist, nod(ODCLFIELD, name, l->n->right));
 	}
 }

src/cmd/gc/dcl.c

@@ -640,8 +640,7 @@ funcargs(Node *nt)
 			// give it a name so escape analysis has nodes to work with
 			snprint(namebuf, sizeof(namebuf), "~anon%d", gen++);
 			n->left = newname(lookup(namebuf));
-			n->left->orig = N;  // signal that the original was absent
-
+			// TODO: n->left->missing = 1;
 		} 
 
 		n->left->op = ONAME;
@@ -815,7 +814,7 @@ structfield(Node *n)
 		break;
 	}
 
-	if(n->left && n->left->op == ONAME && n->left->orig != N) {
+	if(n->left && n->left->op == ONAME) {
 		f->nname = n->left;
 		f->embedded = n->embedded;
 		f->sym = f->nname->sym;
@@ -1177,6 +1176,7 @@ functype(Node *this, NodeList *in, NodeList *out)
 {
 	Type *t;
 	NodeList *rcvr;
+	Sym *s;
 
 	t = typ(TFUNC);
 
@@ -1194,7 +1194,12 @@ functype(Node *this, NodeList *in, NodeList *out)
 		t->thistuple = 1;
 	t->outtuple = count(out);
 	t->intuple = count(in);
-	t->outnamed = t->outtuple > 0 && out->n->left != N && out->n->left->orig != N;
+	t->outnamed = 0;
+	if(t->outtuple > 0 && out->n->left != N && out->n->left->orig != N) {
+		s = out->n->left->orig->sym;
+		if(s != S && s->name[0] != '~')
+			t->outnamed = 1;
+	}
 
 	return t;
 }

src/cmd/gc/fmt.c

@@ -723,12 +723,15 @@ typefmt(Fmt *fp, Type *t)
 		if(!(fp->flags&FmtShort)) {
 			s = t->sym;
 
-			// Take the name from the original, lest we substituted it with .anon%d
-			if ((fmtmode == FErr || fmtmode == FExp) && t->nname != N)
-				if(t->nname->orig != N)
+			// Take the name from the original, lest we substituted it with ~anon%d
+			if ((fmtmode == FErr || fmtmode == FExp) && t->nname != N) {
+				if(t->nname->orig != N) {
 					s = t->nname->orig->sym;
-				else 
+					if(s != S && s->name[0] == '~')
 						s = S;
+				} else 
+					s = S;
+			}
 			
 			if(s != S && !t->embedded) {
 				if(t->funarg)

src/cmd/gc/go.h

@@ -271,7 +271,6 @@ struct	Node
 
 	// most nodes
 	Type*	type;
-	Type*	realtype;	// as determined by typecheck
 	Node*	orig;		// original form, for printing, and tracking copies of ONAMEs
 
 	// func
@@ -1438,7 +1437,7 @@ void	gdata(Node*, Node*, int);
 void	gdatacomplex(Node*, Mpcplx*);
 void	gdatastring(Node*, Strlit*);
 void	genembedtramp(Type*, Type*, Sym*, int iface);
-void	ggloblnod(Node *nam, int32 width);
+void	ggloblnod(Node *nam);
 void	ggloblsym(Sym *s, int32 width, int dupok, int rodata);
 Prog*	gjmp(Prog*);
 void	gused(Node*);

src/cmd/gc/obj.c

@@ -59,7 +59,7 @@ dumpglobls(void)
 			continue;
 		dowidth(n->type);
 
-		ggloblnod(n, n->type->width);
+		ggloblnod(n);
 	}
 
 	for(l=funcsyms; l; l=l->next) {

src/cmd/gc/pgen.c

@@ -14,11 +14,12 @@ compile(Node *fn)
 {
 	Plist *pl;
 	Node nod1, *n;
-	Prog *plocals, *ptxt;
+	Prog *plocals, *ptxt, *p, *p1;
 	int32 lno;
 	Type *t;
 	Iter save;
 	vlong oldstksize;
+	NodeList *l;
 
 	if(newproc == N) {
 		newproc = sysfunc("newproc");
@@ -92,12 +93,25 @@ compile(Node *fn)
 	for(t=curfn->paramfld; t; t=t->down)
 		gtrack(tracksym(t->type));
 
+	for(l=fn->dcl; l; l=l->next) {
+		n = l->n;
+		if(n->op != ONAME) // might be OTYPE or OLITERAL
+			continue;
+		switch(n->class) {
+		case PAUTO:
+		case PPARAM:
+		case PPARAMOUT:
+			nodconst(&nod1, types[TUINTPTR], l->n->type->width);
+			p = gins(ATYPE, l->n, &nod1);
+			p->from.gotype = ngotype(l->n);
+			break;
+		}
+	}
+
 	genlist(curfn->enter);
 
 	retpc = nil;
 	if(hasdefer || curfn->exit) {
-		Prog *p1;
-
 		p1 = gjmp(nil);
 		retpc = gjmp(nil);
 		patch(p1, pc);

src/cmd/gc/subr.c

@@ -3555,10 +3555,8 @@ umagic(Magic *m)
 Sym*
 ngotype(Node *n)
 {
-	if(n->sym != S && n->realtype != T)
-	if(strncmp(n->sym->name, "autotmp_", 8) != 0)
-		return typenamesym(n->realtype);
-
+	if(n->type != T)
+		return typenamesym(n->type);
 	return S;
 }
 

src/cmd/gc/typecheck.c

@@ -296,7 +296,6 @@ typecheck1(Node **np, int top)
 		}
 
 		typecheckdef(n);
-		n->realtype = n->type;
 		if(n->op == ONONAME)
 			goto error;
 	}

src/cmd/gc/walk.c

@@ -2217,6 +2217,8 @@ paramstoheap(Type **argin, int out)
 	nn = nil;
 	for(t = structfirst(&savet, argin); t != T; t = structnext(&savet)) {
 		v = t->nname;
+		if(v && v->sym && v->sym->name[0] == '~')
+			v = N;
 		if(v == N && out && hasdefer) {
 			// Defer might stop a panic and show the
 			// return values as they exist at the time of panic.