[wasm-gc][bug] Restructure DecodeFunction(), add early exits

This fixes a bug caused by StartFunction() being called for an invalid
module.

Bug: v8:7748
Change-Id: I47a3f3573355d87554b123dd1edc7c829bb43d0e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2423710
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70081}

src/wasm/baseline/liftoff-compiler.cc

@@ -4108,7 +4108,10 @@ WasmCompilationResult ExecuteLiftoffCompilation(
   decoder.Decode();
   liftoff_compile_time_scope.reset();
   LiftoffCompiler* compiler = &decoder.interface();
-  if (decoder.failed()) compiler->OnFirstError(&decoder);
+  if (decoder.failed()) {
+    compiler->OnFirstError(&decoder);
+    return WasmCompilationResult{};
+  }
 
   if (counters) {
     // Check that the histogram for the bailout reasons has the correct size.

src/wasm/function-body-decoder-impl.h

@@ -1956,34 +1956,33 @@ class WasmFullDecoder : public WasmDecoder<validate> {
     uint32_t params_count = static_cast<uint32_t>(this->num_locals());
     uint32_t locals_length;
     this->DecodeLocals(this->pc(), &locals_length, params_count);
+    this->consume_bytes(locals_length);
     for (uint32_t index = params_count; index < this->num_locals(); index++) {
       if (!VALIDATE(this->local_type(index).is_defaultable())) {
         this->errorf(
             this->pc(),
             "Cannot define function-level local of non-defaultable type %s",
             this->local_type(index).name().c_str());
+        return this->TraceFailed();
       }
     }
-    this->consume_bytes(locals_length);
 
     CALL_INTERFACE(StartFunction);
     DecodeFunctionBody();
-    if (!this->failed()) CALL_INTERFACE(FinishFunction);
+    if (this->failed()) return TraceFailed();
 
-    // Generate a better error message whether the unterminated control
-    // structure is the function body block or an innner structure.
     if (!VALIDATE(control_.empty())) {
       if (control_.size() > 1) {
         this->error(control_.back().pc, "unterminated control structure");
-      } else if (control_.size() == 1) {
+      } else {
         this->error("function body must end with \"end\" opcode");
       }
+      return TraceFailed();
     }
+    CALL_INTERFACE(FinishFunction);
+    if (this->failed()) return TraceFailed();
 
-    if (!VALIDATE(this->ok())) return this->TraceFailed();
-
-    TRACE("wasm-decode %s\n\n", VALIDATE(this->ok()) ? "ok" : "failed");
-
+    TRACE("wasm-decode ok\n\n");
     return true;
   }
 

src/wasm/graph-builder-interface.cc

@@ -941,6 +941,7 @@ class WasmGraphBuildingInterface {
   }
 
   TFNode* DefaultValue(ValueType type) {
+    DCHECK(type.is_defaultable());
     switch (type.kind()) {
       case ValueType::kI8:
       case ValueType::kI16:

test/unittests/wasm/function-body-decoder-unittest.cc

@@ -3504,7 +3504,8 @@ TEST_F(FunctionBodyDecoderTest, NonDefaultableLocal) {
   WASM_FEATURE_SCOPE(typed_funcref);
   WASM_FEATURE_SCOPE(reftypes);
   AddLocals(ValueType::Ref(HeapType::kExtern, kNonNullable), 1);
-  ExpectFailure(sigs.v_v(), {});
+  ExpectFailure(sigs.v_v(), {}, kAppendEnd,
+                "Cannot define function-level local of non-defaultable type");
 }
 
 TEST_F(FunctionBodyDecoderTest, RefEq) {