[liftoff] Make LiftoffAssembler independent of Isolate.

R=clemensh@chromium.org

Change-Id: Ia3856921a707e7d58d55a74d3f14cbdc0d69eaa5
Reviewed-on: https://chromium-review.googlesource.com/1124332
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54168}

src/wasm/baseline/liftoff-assembler.cc

@@ -336,12 +336,18 @@ void LiftoffAssembler::CacheState::Split(const CacheState& source) {
   *this = source;
 }
 
+namespace {
+
+constexpr Assembler::Options DefaultLiftoffOptions() {
+  return Assembler::Options{};
+}
+
+}  // namespace
+
 // TODO(clemensh): Provide a reasonably sized buffer, based on wasm function
 // size.
-// TODO(mstarzinger): The Isolate is not passed to the base class constructor
-// and only used to derive the default options. Remove the Isolate entirely.
-LiftoffAssembler::LiftoffAssembler(Isolate* isolate)
-    : TurboAssembler(nullptr, Assembler::DefaultOptions(isolate), nullptr, 0,
+LiftoffAssembler::LiftoffAssembler()
+    : TurboAssembler(nullptr, DefaultLiftoffOptions(), nullptr, 0,
                      CodeObjectRequired::kNo) {
   set_trap_on_abort(true);  // Avoid calls to Abort.
 }

src/wasm/baseline/liftoff-assembler.h

@@ -247,7 +247,7 @@ class LiftoffAssembler : public TurboAssembler {
     CacheState(const CacheState&) = delete;
   };
 
-  explicit LiftoffAssembler(Isolate* isolate);
+  LiftoffAssembler();
   ~LiftoffAssembler();
 
   LiftoffRegister PopToRegister(LiftoffRegList pinned = {});

src/wasm/baseline/liftoff-compiler.h

@@ -18,7 +18,7 @@ namespace wasm {
 class LiftoffCompilationUnit final {
  public:
   explicit LiftoffCompilationUnit(WasmCompilationUnit* wasm_unit)
-      : wasm_unit_(wasm_unit), asm_(wasm_unit->isolate_) {}
+      : wasm_unit_(wasm_unit) {}
 
   bool ExecuteCompilation();
   wasm::WasmCode* FinishCompilation(wasm::ErrorThrower*);