scc

commit 00d366a0535adf8b0bf934e398aae138426d7262
parent d603b01749058d99f191934ebbefb0f8a56328eb
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Tue, 31 Dec 2024 18:55:40 +0100

cc2: Add support for switch in the cfg

Switch introduces a new different type of link between basic
blocks because a single basic block can be linked with many
different basic blocks which does not fit well with the
true/false approach that we were using with basic blocks.

Diffstat:
M
src/cmd/scc-cc/cc2/cc2.h
 | 
2
++
M
src/cmd/scc-cc/cc2/cfg.c
 | 
57
++++++++++++++++++++++++++++++++++++++++++++++++++++++---
M
src/cmd/scc-cc/cc2/parser.c
 | 
6
+++++-
M
src/cmd/scc-cc/cc2/swtch.c
 | 
1
-

4 files changed, 61 insertions(+), 5 deletions(-)
diff --git a/src/cmd/scc-cc/cc2/cc2.h b/src/cmd/scc-cc/cc2/cc2.h
@@ -161,6 +161,7 @@ struct swtch {
 	int nr;
 	TINT min, max;
 	Node *defnode;
+	Node *cases;
 	Node *first;
 	Node *last;
 	Swtch *next;
@@ -217,6 +218,7 @@ struct block {
 	int printed, visited;
 	Node *entryp, *exitp;
 	Block *true, *false;
+	Swtch *swtch;
 	Block *next;
 };
 
diff --git a/src/cmd/scc-cc/cc2/cfg.c b/src/cmd/scc-cc/cc2/cfg.c
@@ -29,6 +29,10 @@ static struct cfg cfg;
 static void
 prbb(Block *bb)
 {
+	Node *np;
+	Swtch *swt;
+	Block *casebb;
+
 	if (!bb || bb->printed)
 		return;
 
@@ -46,6 +50,28 @@ prbb(Block *bb)
 	}
 	prbb(bb->true);
 	prbb(bb->false);
+
+	swt = bb->swtch;
+	if (!swt)
+		return;
+
+	for (np = swt->cases; np->op != OESWITCH; np = np->next) {
+		casebb = np->u.sym->u.stmt->bb;
+
+		if (!np->left) {
+			fprintf(stderr,
+				"\t%d -> %d [label=\"default\"]\n",
+			        bb->id,
+			        casebb->id);
+		} else {
+			fprintf(stderr,
+				"\t%d -> %d [label=\"case %lld\"]\n",
+			        bb->id,
+			        casebb->id,
+			        np->left->u.i);
+		}
+		prbb(casebb);
+	}
 }
 
 static void
@@ -84,6 +110,7 @@ newbb(Node *np)
 	bb = &cfg.blocks[cfg.nr];
 	bb->entryp = np;
 	bb->exitp = NULL;
+	bb->swtch = NULL;
 	bb->true = bb->false = NULL;
 	bb->id = cfg.nr++;
 	bb->visited = 0;
@@ -95,9 +122,6 @@ newbb(Node *np)
 static Node *
 mkcfg(Node *np)
 {
-	if ((np->flags & (BBENTRY|BBEXIT)) == 0)
-		return np;
-
 	if (np->flags & BBENTRY)
 		cfg.cur = np->bb;
 
@@ -116,6 +140,12 @@ mkcfg(Node *np)
 	case ORET:
 		cfg.cur->true = laststmt->bb;
 		break;
+	case OBSWITCH:
+		cfg.cur->swtch = np->u.swtch;
+		break;
+	case OESWITCH:
+		cfg.cur->true = NULL;
+		break;
 	case OBRANCH:
 		cfg.cur->false = np->next->bb;
 	case OJMP:
@@ -152,6 +182,9 @@ newentry(Node *np)
 static Node *
 markbb(Node *np)
 {
+	Swtch *swt;
+	Node *p;
+
 	switch (np->op) {
 	case OBFUN:
 		newentry(np);
@@ -160,6 +193,14 @@ markbb(Node *np)
 		newentry(laststmt);
 		newentry(np->next);
 		break;
+	case OBSWITCH:
+		swt = np->u.swtch;
+		for (p = swt->cases; p->op != OESWITCH; p = p->next)
+			newentry(p->u.sym->u.stmt);
+		break;
+	case OESWITCH:
+		np->flags |= BBEXIT;
+		break;
 	case OBRANCH:
 	case OJMP:
 		newentry(np->u.sym->u.stmt);
@@ -172,11 +213,21 @@ markbb(Node *np)
 static void
 visit(Block *bb)
 {
+	Node *np;
+	Swtch *swt;
+
 	if (!bb || bb->visited)
 		return;
 	bb->visited = 1;
 	visit(bb->true);
 	visit(bb->false);
+
+	swt = bb->swtch;
+	if (!swt)
+		return;
+
+	for (np = swt->cases; np->op != OESWITCH; np = np->next)
+		visit(np->u.sym->u.stmt->bb);
 }
 
 static void
diff --git a/src/cmd/scc-cc/cc2/parser.c b/src/cmd/scc-cc/cc2/parser.c
@@ -385,14 +385,18 @@ bswitch(char *token, union tokenop u)
 static void
 eswitch(char *token, union tokenop u)
 {
+	Node *first;
 	Swtch *cur;
 
 	if (swp == swtbl)
 		error(EWTACKU);
 	jump(token, u);
 	waft(pop());
+
 	cur = --swp;
-	cur->first->u.swtch = newswitch(cur);
+	first = cur->first;
+	cur->cases = first->next;
+	first->u.swtch = newswitch(cur);
 }
 
 static void
diff --git a/src/cmd/scc-cc/cc2/swtch.c b/src/cmd/scc-cc/cc2/swtch.c
@@ -66,7 +66,6 @@ swtch_dir(Node *np, int n, TINT min, TINT max)
 		p->type = ptrtype;
 		p->op = OLABEL;
 	}
-	np->next = p->next;
 
 	for (ip = its; ip < &its[n]; ++ip) {
 		if (*ip == NULL)