Support if/else

2 files changed, 117 insertions, 3 deletions

diff --git a/read_instr.c b/read_instr.c
index 805326c..7f7d2a6 100644
--- a/read_instr.c
+++ b/read_instr.c
@@ -358,6 +358,21 @@ static bool branch(const uint8_t op)
     return false;
 }
 
+static bool cbranch(const uint8_t op)
+{
+    switch (op)
+    {
+        case OP_IF:
+        case OP_ELSE:
+            return true;
+
+        default:
+            break;
+    }
+
+    return false;
+}
+
 struct block
 {
     uint8_t op;
@@ -470,7 +485,7 @@ static int add_branch(const uint8_t op, struct lo *const lo, const struct blocks
 
     struct lo_entry *const e = &ve[lo->n++];
 
-    *e = (const struct lo_entry){.b = tgt, .pc = offset};
+    *e = (const struct lo_entry){.op = op, .b = tgt, .pc = offset};
 
     if (tgt->op == OP_LOOP)
         e->dst = tgt->pc;
@@ -479,6 +494,50 @@ static int add_branch(const uint8_t op, struct lo *const lo, const struct blocks
     return 0;
 }
 
+static int add_cbranch(const uint8_t op, struct lo *const lo,
+    const struct blocks *const b, const unsigned level, FILE *const f)
+{
+    const long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        fprintf(stderr, "%s: ftell(3): %s\n", __func__,
+            strerror(errno));
+        return -1;
+    }
+
+    const struct block *tgt = NULL;
+
+    for (const struct block *bl = b->tail; bl; bl = bl->prev)
+        if (bl->op == OP_IF && bl->level == level)
+        {
+            tgt = bl;
+            break;
+        }
+
+    if (!tgt)
+    {
+        fprintf(stderr, "%s: could not find matching block, pc=%ld\n",
+            __func__, offset);
+        return -1;
+    }
+
+    const size_t n = lo->n + 1;
+    struct lo_entry *const ve = realloc(lo->entries, n * sizeof *lo->entries);
+
+    if (!ve)
+    {
+        fprintf(stderr, "%s: realloc(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    struct lo_entry *const e = &ve[lo->n++];
+
+    *e = (const struct lo_entry){.op = op, .b = tgt, .pc = offset};
+    lo->entries = ve;
+    return 0;
+}
+
 static int set_end(struct lo *const lo, const struct blocks *const b,
     const unsigned level, FILE *const f)
 {
@@ -512,7 +571,51 @@ static int set_end(struct lo *const lo, const struct blocks *const b,
     {
         struct lo_entry *const e = &lo->entries[i];
 
-        if (e->b == tgt && tgt->op == OP_BLOCK)
+        if (e->b == tgt)
+        {
+            if (tgt->op == OP_BLOCK)
+                e->dst = offset;
+            else if (tgt->op == OP_IF &&
+                (e->op == OP_ELSE || (e->op == OP_IF && !e->dst)))
+                e->dst = offset;
+        }
+    }
+
+    return 0;
+}
+
+static int set_else(struct lo *const lo, const struct blocks *const b,
+    const unsigned level, FILE *const f)
+{
+    long offset = ftell(f);
+
+    if (offset < 0)
+    {
+        fprintf(stderr, "%s: ftell(3): %s\n", __func__, strerror(errno));
+        return -1;
+    }
+
+    const struct block *tgt = NULL;
+
+    for (const struct block *bl = b->tail; bl; bl = bl->prev)
+        if (bl->level == level && bl->op == OP_IF)
+        {
+            tgt = bl;
+            break;
+        }
+
+    if (!tgt)
+    {
+        fprintf(stderr, "%s: could not find matching block for end, pc=%ld\n",
+            __func__, offset);
+        return -1;
+    }
+
+    for (size_t i = 0; i < lo->n; i++)
+    {
+        struct lo_entry *const e = &lo->entries[i];
+
+        if (e->b == tgt && e->op == OP_IF)
             e->dst = offset;
     }
 
@@ -567,7 +670,17 @@ int read_instr(FILE *const f, struct parse *const p)
         }
         else if (branch(op) && add_branch(op, &lo, &b, relative_depth, level, f))
         {
-            fprintf(stderr, "%s: add_entry failed\n", __func__);
+            fprintf(stderr, "%s: add_branch failed\n", __func__);
+            goto failure;
+        }
+        else if (cbranch(op) && add_cbranch(op, &lo, &b, level, f))
+        {
+            fprintf(stderr, "%s: add_cbranch failed\n", __func__);
+            goto failure;
+        }
+        else if (op == OP_ELSE && set_else(&lo, &b, level, f))
+        {
+            fprintf(stderr, "%s: set_else failed\n", __func__);
             goto failure;
         }
         else if (op == OP_END)
diff --git a/types.h b/types.h
index 323e17e..1702f44 100644
--- a/types.h
+++ b/types.h
@@ -64,6 +64,7 @@ struct parse
     {
         struct lo_entry
         {
+            uint8_t op;
             const struct block *b;
             uint32_t pc, dst;
         } *entries;