[wasm][fuzzer] Generate test before compilation

Generate the test case before compilation, so that we can generate it
even if compilation crashes.
We can only do this when require_valid is true. Otherwise the test case
depends on whether the module compiles or not.

R=ahaas@chromium.org
CC=​khismet@google.com

Bug: v8:11954
Change-Id: I944e867cc7ca631bff749bd67c4b8baff1df1fa9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3074476Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76123}

test/fuzzer/wasm-fuzzer-common.cc

@@ -530,6 +530,10 @@ void WasmExecutionFuzzer::FuzzWasmModule(base::Vector<const uint8_t> data,
   ErrorThrower interpreter_thrower(i_isolate, "Interpreter");
   ModuleWireBytes wire_bytes(buffer.begin(), buffer.end());
 
+  if (require_valid && FLAG_wasm_fuzzer_gen_test) {
+    GenerateTestCase(i_isolate, wire_bytes, true);
+  }
+
   auto enabled_features = i::wasm::WasmFeatures::FromIsolate(i_isolate);
   MaybeHandle<WasmModuleObject> compiled_module;
   {
@@ -544,8 +548,7 @@ void WasmExecutionFuzzer::FuzzWasmModule(base::Vector<const uint8_t> data,
         i_isolate, enabled_features, &interpreter_thrower, wire_bytes);
   }
   bool compiles = !compiled_module.is_null();
-
-  if (FLAG_wasm_fuzzer_gen_test) {
+  if (!require_valid && FLAG_wasm_fuzzer_gen_test) {
     GenerateTestCase(i_isolate, wire_bytes, compiles);
   }