[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, 47 insertions, 0 deletions

diff --git a/wasm/runtime.c b/wasm/runtime.c
new file mode 100644
index 0000000000..b5b0a1a966
--- /dev/null
+++ b/wasm/runtime.c
@@ -0,0 +1,47 @@
+#include "wasm/machine.h"
+#include "wasm/setjmp.h"
+#include "wasm/fiber.h"
+#include "wasm/asyncify.h"
+#include <stdlib.h>
+
+int rb_wasm_rt_start(int (main)(int argc, char **argv), int argc, char **argv) {
+  int result;
+  void *asyncify_buf;
+
+  bool new_fiber_started = false;
+  void *arg0 = NULL, *arg1 = NULL;
+  void (*fiber_entry_point)(void *, void *) = NULL;
+
+  while (1) {
+    if (fiber_entry_point) {
+      fiber_entry_point(arg0, arg1);
+    } else {
+      result = main(argc, argv);
+    }
+
+    // NOTE: it's important to call 'asyncify_stop_unwind' here instead in rb_wasm_handle_jmp_unwind
+    // because unless that, Asyncify inserts another unwind check here and it unwinds to the root frame.
+    asyncify_stop_unwind();
+
+    if ((asyncify_buf = rb_wasm_handle_jmp_unwind()) != NULL) {
+      asyncify_start_rewind(asyncify_buf);
+      continue;
+    }
+    if ((asyncify_buf = rb_wasm_handle_scan_unwind()) != NULL) {
+      asyncify_start_rewind(asyncify_buf);
+      continue;
+    }
+
+    asyncify_buf = rb_wasm_handle_fiber_unwind(&fiber_entry_point, &arg0, &arg1, &new_fiber_started);
+    // Newly starting fiber doesn't have asyncify buffer yet, so don't rewind it for the first time entry
+    if (asyncify_buf) {
+      asyncify_start_rewind(asyncify_buf);
+      continue;
+    } else if (new_fiber_started) {
+      continue;
+    }
+
+    break;
+  }
+  return result;
+}