1 files changed, 121 insertions, 0 deletions
diff --git a/ifopt.c b/ifopt.c
new file mode 100644
index 0000000..3e45f52
--- /dev/null
+++ b/ifopt.c
@@ -0,0 +1,121 @@
+#include "all.h"
+
+enum {
+	MaxIns = 2,
+	MaxPhis = 2,
+};
+
+static int
+okbranch(Blk *b)
+{
+	Ins *i;
+	int n;
+
+	n = 0;
+	for (i=b->ins; i<&b->ins[b->nins]; i++)
+		if (i->op != Odbgloc) {
+			if (pinned(i))
+				return 0;
+			if (i->op != Onop)
+				n++;
+		}
+	return n <= MaxIns;
+}
+
+static int
+okjoin(Blk *b)
+{
+	Phi *p;
+	int n;
+
+	n = 0;
+	for (p=b->phi; p; p=p->link) {
+		if (KBASE(p->cls) != 0)
+			return 0;
+		n++;
+	}
+	return n <= MaxPhis;
+}
+
+static int
+okgraph(Blk *ifb, Blk *thenb, Blk *elseb, Blk *joinb)
+{
+	if (joinb->npred != 2 || !okjoin(joinb))
+		return 0;
+	assert(thenb != elseb);
+	if (thenb != ifb && !okbranch(thenb))
+		return 0;
+	if (elseb != ifb && !okbranch(elseb))
+		return 0;
+	return 1;
+}
+
+static void
+convert(Blk *ifb, Blk *thenb, Blk *elseb, Blk *joinb)
+{
+	Ins *ins, sel;
+	Phi *p;
+	uint nins;
+
+	ins = vnew(0, sizeof ins[0], PHeap);
+	nins = 0;
+	addbins(&ins, &nins, ifb);
+	if (thenb != ifb)
+		addbins(&ins, &nins, thenb);
+	if (elseb != ifb)
+		addbins(&ins, &nins, elseb);
+	assert(joinb->npred == 2);
+	if (joinb->phi) {
+		sel = (Ins){
+			.op = Osel0, .cls = Kw,
+			.arg = {ifb->jmp.arg},
+		};
+		addins(&ins, &nins, &sel);
+	}
+	sel = (Ins){.op = Osel1};
+	for (p=joinb->phi; p; p=p->link) {
+		sel.to = p->to;
+		sel.cls = p->cls;
+		sel.arg[0] = phiarg(p, thenb);
+		sel.arg[1] = phiarg(p, elseb);
+		addins(&ins, &nins, &sel);
+	}
+	idup(ifb, ins, nins);
+	ifb->jmp.type = Jjmp;
+	ifb->jmp.arg = R;
+	ifb->s1 = joinb;
+	ifb->s2 = 0;
+	joinb->npred = 1;
+	joinb->pred[0] = ifb;
+	joinb->phi = 0;
+	vfree(ins);
+}
+
+/* eliminate if-then[-else] graphlets
+ * using sel instructions
+ * needs rpo pred use; breaks cfg use
+ */
+void
+ifconvert(Fn *fn)
+{
+	Blk *ifb, *thenb, *elseb, *joinb;
+
+	if (debug['K'])
+		fputs("\n> If-conversion:\n", stderr);
+
+	for (ifb=fn->start; ifb; ifb=ifb->link)
+		if (ifgraph(ifb, &thenb, &elseb, &joinb))
+		if (okgraph(ifb, thenb, elseb, joinb)) {
+			if (debug['K'])
+				fprintf(stderr,
+					"    @%s -> @%s, @%s -> @%s\n",
+					ifb->name, thenb->name, elseb->name,
+					joinb->name);
+			convert(ifb, thenb, elseb, joinb);
+		}
+
+	if (debug['K']) {
+		fprintf(stderr, "\n> After if-conversion:\n");
+		printfn(fn, stderr);
+	}
+}