[9front] draft: kill rathole ("non-interruptible temporary")

[ori@eigenstate.org]

Currently, kencc generates temporaries into a global
rathole, rahter than putting them onto the stack; this
means that any code with a 'non-interruptible
temporary' not thread or note safe.

this code takes a first pass at removing it from kencc,
using 'regsalloc' to store them on the stack.

There's no attempt at reuse, so there may be room for
improvement, but given that we don't use so many
temporaries this way, it seems acceptable to just leave
them on the stack until the function exits.

this has only been tested lightly, and hasn't built more
than a few dozen lines of test code, so it's nowhere near
ready to commit; it's just presented for comment.

any thoughts on the approach? anything obvious I missed?

diff f305820f8891305ad73afa67ed2585b69d4054d8 uncommitted
--- a/6c/cgen.c
+++ b/6c/cgen.c
@@ -1016,17 +1016,14 @@
 		break;
 
 	case ODOT:
-		sugen(l, nodrat, l->type->width);
+		regsalloc(&nod, l);
+		sugen(l, &nod, l->type->width);
 		if(nn == Z)
 			break;
-		warn(n, "non-interruptable temporary");
-		nod = *nodrat;
 		if(!r || r->op != OCONST) {
 			diag(n, "DOT and no offset");
 			break;
 		}
-		nod.xoffset += (long)r->vconst;
-		nod.type = n->type;
 		cgen(&nod, nn);
 		break;
 
@@ -1409,9 +1406,6 @@
 		prtree(nn, "sugen lhs");
 		prtree(n, "sugen");
 	}
-	if(nn == nodrat)
-		if(w > nrathole)
-			nrathole = w;
 	switch(n->op) {
 	case OIND:
 		if(nn == Z) {
@@ -1427,18 +1421,15 @@
 
 	case ODOT:
 		l = n->left;
-		sugen(l, nodrat, l->type->width);
+		regsalloc(&nod1, l);
+		sugen(l, &nod1, l->type->width);
 		if(nn == Z)
 			break;
-		warn(n, "non-interruptable temporary");
-		nod1 = *nodrat;
 		r = n->right;
 		if(!r || r->op != OCONST) {
 			diag(n, "DOT and no offset");
 			break;
 		}
-		nod1.xoffset += (long)r->vconst;
-		nod1.type = n->type;
 		sugen(&nod1, nn, w);
 		break;
 
@@ -1524,15 +1515,17 @@
 			break;
 		}
 
-		sugen(n->right, nodrat, w);
+		regsalloc(&nod0, n->right);
+		sugen(n->right, &nod0, w);
 		warn(n, "non-interruptable temporary");
-		sugen(nodrat, n->left, w);
-		sugen(nodrat, nn, w);
+		sugen(&nod0, n->left, w);
+		sugen(&nod0, nn, w);
 		break;
 
 	case OFUNC:
 		if(nn == Z) {
-			sugen(n, nodrat, w);
+			regsalloc(&nod0, n);
+			sugen(n, &nod0, w);
 			break;
 		}
 		if(nn->op != OIND) {
--- a/6c/gc.h
+++ b/6c/gc.h
@@ -144,10 +144,8 @@
 EXTERN	Prog*	lastp;
 EXTERN	long	maxargsafe;
 EXTERN	int	mnstring;
-EXTERN	Node*	nodrat;
 EXTERN	Node*	nodret;
 EXTERN	Node*	nodsafe;
-EXTERN	long	nrathole;
 EXTERN	long	nstring;
 EXTERN	Prog*	p;
 EXTERN	long	pc;
@@ -154,7 +152,6 @@
 EXTERN	Node	lregnode;
 EXTERN	Node	qregnode;
 EXTERN	char	string[NSNAME];
-EXTERN	Sym*	symrathole;
 EXTERN	Node	znode;
 EXTERN	Prog	zprog;
 EXTERN	int	reg[D_NONE];
--- a/6c/swt.c
+++ b/6c/swt.c
@@ -350,7 +350,7 @@
 	char *n;
 	ulong sig;
 
-	if(debug['T'] && t == D_EXTERN && s->sig != SIGDONE && s->type != types[TENUM] && s != symrathole){
+	if(debug['T'] && t == D_EXTERN && s->sig != SIGDONE){
 		sig = sign(s);
 		Bputc(b, ASIGNAME);
 		Bputc(b, ASIGNAME>>8);
--- a/6c/test.c
+++ b/6c/test.c
@@ -1,17 +1,22 @@
 #include <u.h>
 #include <libc.h>
 
+typedef struct S S;
+
+struct S{
+	int x;
+	int y;
+};
+
+S
+fn(void)
+{
+	static int ncall;
+	return (S){1, ncall++};
+}
+
 void
 main(void)
 {
-	uvlong a;
-	vlong b;
-	
-	a = 0xFFFFFFFF80000000;
-	b = 0xFFFFFFFF;
-	
-	
-	print("%ullX %llX, %ullX %ullX\n", a, b, (uvlong)0xffffffff);
-	exits(nil);
+	print("x: %d, y0:%d y1:%d y2: %d\n", fn().x, fn().y, fn().y, fn().y);
 }
-
--- a/6c/txt.c
+++ b/6c/txt.c
@@ -6,7 +6,6 @@
 ginit(void)
 {
 	int i;
-	Type *t;
 
 	thechar = '6';
 	thestring = "amd64";
@@ -15,7 +14,6 @@
 	listinit();
 	nstring = 0;
 	mnstring = 0;
-	nrathole = 0;
 	pc = 0;
 	breakpc = -1;
 	continpc = -1;
@@ -72,19 +70,6 @@
 	nodsafe->class = CAUTO;
 	complex(nodsafe);
 
-	t = typ(TARRAY, types[TCHAR]);
-	symrathole = slookup(".rathole");
-	symrathole->class = CGLOBL;
-	symrathole->type = t;
-
-	nodrat = new(ONAME, Z, Z);
-	nodrat->sym = symrathole;
-	nodrat->type = types[TIND];
-	nodrat->etype = TVOID;
-	nodrat->class = CGLOBL;
-	complex(nodrat);
-	nodrat->type = t;
-
 	nodret = new(ONAME, Z, Z);
 	nodret->sym = slookup(".ret");
 	nodret->type = types[TIND];
@@ -126,7 +111,6 @@
 	while(mnstring)
 		outstring("", 1L);
 	symstring->type->width = nstring;
-	symrathole->type->width = nrathole;
 	for(i=0; i<NHASH; i++)
 	for(s = hash[i]; s != S; s = s->link) {
 		if(s->type == T)