From 6d9d80362f9932bbc87e162b8ef7df06c73e27e1 Mon Sep 17 00:00:00 2001
From: Xavier Del Campo Romero <xavi.dcr@tutanota.com>
Date: Sat, 7 Sep 2024 00:04:38 +0200
Subject: First commit

---
 src/op/drop.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 src/op/drop.c

(limited to 'src/op/drop.c')

diff --git a/src/op/drop.c b/src/op/drop.c
new file mode 100644
index 0000000..3b5dffd
--- /dev/null
+++ b/src/op/drop.c
@@ -0,0 +1,101 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nw/interp.h>
+#include <nw/io.h>
+#include <nw/log.h>
+#include <nw/opcodes.h>
+#include <nw/ops.h>
+#include <nw/stack.h>
+#include <nw/types.h>
+
+static enum nw_state pop(struct nw_interp *const i)
+{
+    struct nw_i_sm_drop *const d = &i->sm.drop;
+    const enum nw_state n = nwp_stack_pop(i, &d->io);
+
+    if (n)
+        return n;
+
+    nwp_interp_resume(i);
+    return NW_AGAIN;
+}
+
+static enum nw_state check(struct nw_interp *const i)
+{
+    struct nw_i_sm_drop *const d = &i->sm.drop;
+    const struct nw_frame *const fr = &i->fr;
+    const struct nw_return *const r = &fr->prev_ret;
+    const unsigned char prev = fr->prev_op;
+    size_t sz;
+
+    if (prev != OP_CALL && prev != OP_CALL_INDIRECT)
+    {
+        static const char *const exc =
+            "expected call or call_indirect before drop";
+
+        i->exception = exc;
+#ifdef NW_LOG
+        nwp_log("%s, got: %#x\n", exc, (unsigned)prev);
+#endif
+        return NW_FATAL;
+    }
+    else if (!r->count)
+    {
+        static const char *const exc =
+            "called drop from function without return value";
+
+        i->exception = exc;
+#ifdef NW_LOG
+        nwp_log("%s\n", exc);
+#endif
+        return NW_FATAL;
+    }
+    else if (r->type != i->push_type)
+    {
+        static const char *const exc =
+            "mismatch between return type and last push type";
+
+        i->exception = exc;
+#ifdef NW_LOG
+        nwp_log("%s, expected: %#hhx, got: %#hhx\n", exc,
+            (unsigned char)i->push_type, (unsigned char)r->type);
+#endif
+        return NW_FATAL;
+    }
+    else if (nwp_type_sz(r->type, &sz))
+    {
+        static const char *const exc = "invalid return type";
+
+        i->exception = exc;
+#ifdef NW_LOG
+        nwp_log("%s: %#x\n", exc, (unsigned)r->type);
+#endif
+        return NW_FATAL;
+    }
+    else
+    {
+        struct nw_sm_io io = {0};
+
+        io.buf = &d->value;
+        io.n = sz;
+        d->io = io;
+        i->next = pop;
+    }
+
+    return NW_AGAIN;
+}
+
+void nwp_op_drop(struct nw_interp *const i)
+{
+    const struct nw_i_sm_drop d = {{0}};
+
+    i->sm.drop = d;
+    i->next = check;
+}
-- 
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