wasm: add flag to dump modules

src/wasm/module-decoder.cc

Index: src/wasm/module-decoder.cc
diff --git a/src/wasm/module-decoder.cc b/src/wasm/module-decoder.cc
index 2c5bea4869df21470b5f583af6c71ea22370c5d5..558d17c5a6e1117e8cf4f9c37f52faaef43e965d 100644
--- a/src/wasm/module-decoder.cc
+++ b/src/wasm/module-decoder.cc
@@ -2,12 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "src/wasm/module-decoder.h"
+
+#include "src/base/functional.h"
+#include "src/base/platform/platform.h"
 #include "src/macro-assembler.h"
 #include "src/objects.h"
 #include "src/v8.h"
 
 #include "src/wasm/decoder.h"
-#include "src/wasm/module-decoder.h"
 
 namespace v8 {
 namespace internal {
@@ -40,6 +43,31 @@ class ModuleDecoder : public Decoder {
     pc_ = limit_;  // On error, terminate section decoding loop.
   }
 
+  static void DumpModule(WasmModule* module, ModuleResult result) {
+    std::string path;
+    if (FLAG_dump_wasm_module_path) {
+      path = FLAG_dump_wasm_module_path;
+      if (path.size() &&
+          !base::OS::isDirectorySeparator(path[path.size() - 1])) {
+        path += base::OS::DirectorySeparator();
+      }
+    }
+    // File are named `HASH.{ok,failed}.wasm`.
+    size_t hash = base::hash_range(module->module_start, module->module_end);
+    char buf[32] = {'\0'};
+#if V8_OS_WIN && _MSC_VER < 1900
+#define snprintf sprintf_s
+#endif
+    snprintf(buf, sizeof(buf) - 1, "%016zx.%s.wasm", hash,
+             result.ok() ? "ok" : "failed");
+    std::string name(buf);
+    if (FILE* wasm_file = base::OS::FOpen((path + name).c_str(), "wb")) {
+      fwrite(module->module_start, module->module_end - module->module_start, 1,
+             wasm_file);
+      fclose(wasm_file);
+    }
+  }
+
   // Decodes an entire module.
   ModuleResult DecodeModule(WasmModule* module, bool verify_functions = true) {
     pc_ = start_;
@@ -61,17 +89,19 @@ class ModuleDecoder : public Decoder {
             "expected magic word %02x %02x %02x %02x, "
             "found %02x %02x %02x %02x",
             BYTES(kWasmMagic), BYTES(magic_word));
-      return toResult(module);
+      goto done;
     }
 
     pos = pc_;
-    uint32_t magic_version = consume_u32("wasm version");
-    if (magic_version != kWasmVersion) {
-      error(pos, pos,
-            "expected version %02x %02x %02x %02x, "
-            "found %02x %02x %02x %02x",
-            BYTES(kWasmVersion), BYTES(magic_version));
-      return toResult(module);
+    {
+      uint32_t magic_version = consume_u32("wasm version");
+      if (magic_version != kWasmVersion) {
+        error(pos, pos,
+              "expected version %02x %02x %02x %02x, "
+              "found %02x %02x %02x %02x",
+              BYTES(kWasmVersion), BYTES(magic_version));
+        goto done;
+      }
     }
 
     // Decode the module sections.
@@ -366,7 +396,12 @@ class ModuleDecoder : public Decoder {
       }
     }
 
-    return toResult(module);
+  done:
+    ModuleResult result = toResult(module);
+    if (FLAG_dump_wasm_module) {
+      DumpModule(module, result);
+    }
+    return result;
   }
 
   uint32_t SafeReserve(uint32_t count) {
@@ -399,13 +434,13 @@ class ModuleDecoder : public Decoder {
   FunctionResult DecodeSingleFunction(ModuleEnv* module_env,
                                       WasmFunction* function) {
     pc_ = start_;
-    function->sig = consume_sig();               // read signature
-    function->name_offset = 0;                   // ---- name
-    function->name_length = 0;                   // ---- name length
-    function->code_start_offset = off(pc_);      // ---- code start
-    function->code_end_offset = off(limit_);     // ---- code end
-    function->exported = false;                  // ---- exported
-    function->external = false;                  // ---- external
+    function->sig = consume_sig();            // read signature
+    function->name_offset = 0;                // ---- name
+    function->name_length = 0;                // ---- name length
+    function->code_start_offset = off(pc_);   // ---- code start
+    function->code_end_offset = off(limit_);  // ---- code end
+    function->exported = false;               // ---- exported
+    function->external = false;               // ---- external
 
     if (ok()) VerifyFunctionBody(0, module_env, function);