From 4fa48e716d6381e51ae8dc7a9992c4c7d50219a1 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Mon, 27 Jun 2022 13:11:50 -0700
Subject: qbe: Insert dead block when compiling unreachable code after a jump

QBE will optimize out these blocks, and the dead block prevents the
possibility of NULL value usage when further control flow follows.

Fixes #80.
---
 qbe.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/qbe.c b/qbe.c
index b95af9e..d24d963 100644
--- a/qbe.c
+++ b/qbe.c
@@ -246,9 +246,12 @@ static struct value *
 funcinst(struct func *f, int op, int class, struct value *arg0, struct value *arg1)
 {
 	struct inst *inst;
+	struct block *b;
 
-	if (f->end->jump.kind)
-		return NULL;
+	if (f->end->jump.kind) {
+		b = mkblock("dead");
+		funclabel(f, b);
+	}
 	inst = mkinst(f, op, class, arg0, arg1);
 	arrayaddptr(&f->end->insts, inst);
 	return &inst->res;
-- 
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