[wasm] add asyncify based setjmp, fiber, register scan emulation

configure.ac: setup build tools and register objects

main.c: wrap main with rb_wasm_rt_start to handle asyncify unwinds

tool/m4/ruby_wasm_tools.m4: setup default command based on WASI_SDK_PATH
environment variable. checks wasm-opt which is used for asyncify.

tool/wasm-clangw wasm/wasm-opt: a clang wrapper which replaces real
wasm-opt with do-nothing wasm-opt to avoid misoptimization before
asyncify. asyncify is performed at POSTLINK, but clang linker driver
tries to run optimization by wasm-opt unconditionally. inlining pass
at wasm level breaks asyncify's assumption, so should not optimize
before POSTLIK.

wasm/GNUmakefile.in: wasm specific rules to compile objects

1 files changed, 62 insertions, 0 deletions

diff --git a/wasm/machine.c b/wasm/machine.c
new file mode 100644
index 0000000000..238041f93e
--- /dev/null
+++ b/wasm/machine.c
@@ -0,0 +1,62 @@
+#include <stdlib.h>
+#include "wasm/machine.h"
+#include "wasm/asyncify.h"
+
+#ifndef WASM_SCAN_STACK_BUFFER_SIZE
+# define WASM_SCAN_STACK_BUFFER_SIZE 6144
+#endif
+
+struct asyncify_buf {
+    void *top;
+    void *end;
+    uint8_t buffer[WASM_SCAN_STACK_BUFFER_SIZE];
+};
+
+static void
+init_asyncify_buf(struct asyncify_buf* buf)
+{
+    buf->top = &buf->buffer[0];
+    buf->end = &buf->buffer[WASM_SCAN_STACK_BUFFER_SIZE];
+}
+
+static void *_rb_wasm_active_scan_buf = NULL;
+
+void
+rb_wasm_scan_locals(rb_wasm_scan_func scan)
+{
+    static struct asyncify_buf buf;
+    static int spilling = 0;
+    if (!spilling) {
+        spilling = 1;
+        init_asyncify_buf(&buf);
+        _rb_wasm_active_scan_buf = &buf;
+        asyncify_start_unwind(&buf);
+    } else {
+        asyncify_stop_rewind();
+        spilling = 0;
+        _rb_wasm_active_scan_buf = NULL;
+        scan(buf.top, buf.end);
+    }
+}
+
+static void *rb_wasm_stack_base = NULL;
+
+__attribute__((constructor))
+int
+rb_wasm_record_stack_base(void)
+{
+    rb_wasm_stack_base = rb_wasm_get_stack_pointer();
+    return 0;
+}
+
+void
+_rb_wasm_scan_stack(rb_wasm_scan_func scan, void *current)
+{
+    scan(current, rb_wasm_stack_base);
+}
+
+void *
+rb_wasm_handle_scan_unwind(void)
+{
+    return _rb_wasm_active_scan_buf;
+}