Reland "[wasm] --liftoff-only should disable --wasm-dynamic-tiering"

This is a reland of commit 54e360d1.
The two WasmGC cctests which require SSE4.1 support in Liftoff are now
skipped, so we can keep disallowing any bailout (even for missing CPU
features) in --liftoff-only.

Original change's description:
> [wasm] --liftoff-only should disable --wasm-dynamic-tiering
>
> A Liftoff only configuration should never tier up to TurboFan, hence add
> a proper implication to disable dynamic tiering if --liftoff-only is
> set.
> Also, add a DCHECK to ensure we never accidentally compile with TurboFan
> if --liftoff-only is set.
>
> R=jkummerow@chromium.org
>
> Bug: v8:12281
> Change-Id: Ia9b81add503cc939f59fde3f4d3bb67252facf2c
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3569741
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Commit-Queue: Clemens Backes <clemensb@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79779}

Bug: v8:12281
Change-Id: I334bd81f75c3ef6d31b6117da5ef59a33fb46ae2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3572043Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79813}

src/compiler/wasm-compiler.cc

@@ -8445,6 +8445,10 @@ wasm::WasmCompilationResult ExecuteTurbofanWasmCompilation(
     wasm::CompilationEnv* env, const wasm::WireBytesStorage* wire_byte_storage,
     const wasm::FunctionBody& func_body, int func_index, Counters* counters,
     wasm::WasmFeatures* detected) {
+  // Check that we do not accidentally compile a Wasm function to TurboFan if
+  // --liftoff-only is set.
+  DCHECK(!FLAG_liftoff_only);
+
   TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("v8.wasm.detailed"),
                "wasm.CompileTopTier", "func_index", func_index, "body_size",
                func_body.end - func_body.start);

src/flags/flag-definitions.h

@@ -1008,6 +1008,7 @@ DEFINE_BOOL(liftoff_only, false,
             "disallow TurboFan compilation for WebAssembly (for testing)")
 DEFINE_IMPLICATION(liftoff_only, liftoff)
 DEFINE_NEG_IMPLICATION(liftoff_only, wasm_tier_up)
+DEFINE_NEG_IMPLICATION(liftoff_only, wasm_dynamic_tiering)
 DEFINE_NEG_IMPLICATION(fuzzing, liftoff_only)
 DEFINE_DEBUG_BOOL(
     enable_testing_opcode_in_wasm, false,

src/wasm/baseline/liftoff-compiler.cc

@@ -293,16 +293,16 @@ void CheckBailoutAllowed(LiftoffBailoutReason reason, const char* detail,
   // Decode errors are ok.
   if (reason == kDecodeError) return;
 
-  // Missing CPU features are also generally OK for now.
-  if (reason == kMissingCPUFeature) return;
-
   // --liftoff-only ensures that tests actually exercise the Liftoff path
-  // without bailing out. Bailing out due to (simulated) lack of CPU support
-  // is okay though (see above).
+  // without bailing out. We also fail for missing CPU support, to avoid
+  // running any TurboFan code under --liftoff-only.
   if (FLAG_liftoff_only) {
     FATAL("--liftoff-only: treating bailout as fatal error. Cause: %s", detail);
   }
 
+  // Missing CPU features are generally OK, except with --liftoff-only.
+  if (reason == kMissingCPUFeature) return;
+
   // If --enable-testing-opcode-in-wasm is set, we are expected to bailout with
   // "testing opcode".
   if (FLAG_enable_testing_opcode_in_wasm &&

test/cctest/wasm/test-gc.cc

@@ -172,6 +172,19 @@ class WasmGCTester {
     CheckHasThrownImpl(function_index, sig, &packer, expected);
   }
 
+  bool HasSimdSupport(TestExecutionTier tier) const {
+#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
+    // Liftoff does not have a fallback for executing SIMD instructions if
+    // SSE4_1 is not available.
+    if (tier == TestExecutionTier::kLiftoff &&
+        !CpuFeatures::IsSupported(SSE4_1)) {
+      return false;
+    }
+#endif
+    USE(tier);
+    return true;
+  }
+
   Handle<WasmInstanceObject> instance() { return instance_; }
   Isolate* isolate() { return isolate_; }
   WasmModuleBuilder* builder() { return &builder_; }
@@ -920,6 +933,7 @@ TEST(WasmLetInstruction) {
 
 WASM_COMPILED_EXEC_TEST(WasmBasicArray) {
   WasmGCTester tester(execution_tier);
+  if (!tester.HasSimdSupport(execution_tier)) return;
 
   const byte type_index = tester.DefineArray(wasm::kWasmI32, true);
   const byte fp_type_index = tester.DefineArray(wasm::kWasmF64, true);
@@ -1310,6 +1324,7 @@ WASM_COMPILED_EXEC_TEST(WasmArrayCopy) {
 
 WASM_COMPILED_EXEC_TEST(NewDefault) {
   WasmGCTester tester(execution_tier);
+  if (!tester.HasSimdSupport(execution_tier)) return;
 
   tester.builder()->StartRecursiveTypeGroup();
   const byte struct_type = tester.DefineStruct(