[wasm] Add the wasm-interpret-all flag

If this flag is set, all code will be executed in the interpreter.
At some point in the future we might want to have a variant for testing
all code with this flag. Currently, I am using it for finding
unimplemented functionality in the interpreter and testing existing
functionality.
Mjsunit tests in follow-up CLs will use this flag too.

R=ahaas@chromium.org, titzer@chromium.org
BUG=v8:5822

Change-Id: I1393b4aedbb9f9070e011362ec95cb89f296dab4
Reviewed-on: https://chromium-review.googlesource.com/453700
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43773}

src/flag-definitions.h

@@ -588,6 +588,8 @@ DEFINE_BOOL(wasm_trap_if, true,
 DEFINE_BOOL(wasm_code_fuzzer_gen_test, false,
             "Generate a test case when running the wasm-code fuzzer")
 DEFINE_BOOL(print_wasm_code, false, "Print WebAssembly code")
+DEFINE_BOOL(wasm_interpret_all, false,
+            "Execute all wasm code in the wasm interpreter")
 
 // Profiler flags.
 DEFINE_INT(frame_count, 1, "number of stack frames inspected by the profiler")

src/wasm/wasm-module.cc

@@ -1314,11 +1314,22 @@ class InstantiationHelper {
     }
 
     //--------------------------------------------------------------------------
-    // Set all breakpoints that were set on the shared module.
+    // Debugging support.
     //--------------------------------------------------------------------------
+    // Set all breakpoints that were set on the shared module.
     WasmSharedModuleData::SetBreakpointsOnNewInstance(
         compiled_module_->shared(), instance);
 
+    if (FLAG_wasm_interpret_all) {
+      Handle<WasmDebugInfo> debug_info =
+          WasmInstanceObject::GetOrCreateDebugInfo(instance);
+      for (int func_index = num_imported_functions,
+               num_wasm_functions = static_cast<int>(module_->functions.size());
+           func_index < num_wasm_functions; ++func_index) {
+        WasmDebugInfo::RedirectToInterpreter(debug_info, func_index);
+      }
+    }
+
     //--------------------------------------------------------------------------
     // Run the start function if one was specified.
     //--------------------------------------------------------------------------