[assembler] Make {PredictableCodeSizeScope} more robust.

R=clemensh@chromium.org

Change-Id: Ia7c18afb10b4198b690b3bc788b8969595d6b0de
Reviewed-on: https://chromium-review.googlesource.com/925303
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51379}

src/arm/code-stubs-arm.cc

@@ -577,8 +577,8 @@ void ProfileEntryHookStub::MaybeCallEntryHookDelayed(TurboAssembler* tasm,
                                                      Zone* zone) {
   if (tasm->isolate()->function_entry_hook() != nullptr) {
     tasm->MaybeCheckConstPool();
-    PredictableCodeSizeScope predictable(tasm);
-    predictable.ExpectSize(tasm->CallStubSize() + 2 * Assembler::kInstrSize);
+    PredictableCodeSizeScope predictable(
+        tasm, tasm->CallStubSize() + 2 * Assembler::kInstrSize);
     tasm->push(lr);
     tasm->CallStubDelayed(new (zone) ProfileEntryHookStub(nullptr));
     tasm->pop(lr);
@@ -589,8 +589,8 @@ void ProfileEntryHookStub::MaybeCallEntryHook(MacroAssembler* masm) {
   if (masm->isolate()->function_entry_hook() != nullptr) {
     ProfileEntryHookStub stub(masm->isolate());
     masm->MaybeCheckConstPool();
-    PredictableCodeSizeScope predictable(masm);
-    predictable.ExpectSize(masm->CallStubSize() + 2 * Assembler::kInstrSize);
+    PredictableCodeSizeScope predictable(
+        masm, masm->CallStubSize() + 2 * Assembler::kInstrSize);
     __ push(lr);
     __ CallStub(&stub);
     __ pop(lr);

src/assembler.cc

@@ -195,9 +195,6 @@ void AssemblerBase::Print(Isolate* isolate) {
 // -----------------------------------------------------------------------------
 // Implementation of PredictableCodeSizeScope
 
-PredictableCodeSizeScope::PredictableCodeSizeScope(AssemblerBase* assembler)
-    : PredictableCodeSizeScope(assembler, -1) {}
-
 PredictableCodeSizeScope::PredictableCodeSizeScope(AssemblerBase* assembler,
                                                    int expected_size)
     : assembler_(assembler),
@@ -208,10 +205,7 @@ PredictableCodeSizeScope::PredictableCodeSizeScope(AssemblerBase* assembler,
 }
 
 PredictableCodeSizeScope::~PredictableCodeSizeScope() {
-  // TODO(svenpanne) Remove the 'if' when everything works.
-  if (expected_size_ >= 0) {
-    CHECK_EQ(expected_size_, assembler_->pc_offset() - start_offset_);
-  }
+  CHECK_EQ(expected_size_, assembler_->pc_offset() - start_offset_);
   assembler_->set_predictable_code_size(old_value_);
 }
 

src/assembler.h

@@ -217,16 +217,14 @@ class DontEmitDebugCodeScope BASE_EMBEDDED {
 // snapshot and the running VM.
 class PredictableCodeSizeScope {
  public:
-  explicit PredictableCodeSizeScope(AssemblerBase* assembler);
   PredictableCodeSizeScope(AssemblerBase* assembler, int expected_size);
   ~PredictableCodeSizeScope();
-  void ExpectSize(int expected_size) { expected_size_ = expected_size; }
 
  private:
-  AssemblerBase* assembler_;
-  int expected_size_;
-  int start_offset_;
-  bool old_value_;
+  AssemblerBase* const assembler_;
+  int const expected_size_;
+  int const start_offset_;
+  bool const old_value_;
 };