Clear exceptions in Invoke instead of JSEntryStub

A corresponding flag was added as well to help us find out what breaks when we
do not clear pending exceptions on each JS entry.

BUG=5259

Review-Url: https://codereview.chromium.org/2208663002
Cr-Commit-Position: refs/heads/master@{#38292}

src/arm/code-stubs-arm.cc

@@ -1105,12 +1105,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
   // restores all kCalleeSaved registers (including cp and fp) to their
   // saved values before returning a failure to C.
 
-  // Clear any pending exceptions.
-  __ mov(r5, Operand(isolate()->factory()->the_hole_value()));
-  __ mov(ip, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
-                                       isolate())));
-  __ str(r5, MemOperand(ip));
-
   // Invoke the function by calling through JS entry trampoline builtin.
   // Notice that we cannot store a reference to the trampoline code directly in
   // this stub, because runtime stubs are not traversed when doing GC.

src/arm64/code-stubs-arm64.cc

@@ -1214,12 +1214,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
   // restores all callee-saved registers (including cp and fp) to their
   // saved values before returning a failure to C.
 
-  // Clear any pending exceptions.
-  __ Mov(x10, Operand(isolate()->factory()->the_hole_value()));
-  __ Mov(x11, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
-                                        isolate())));
-  __ Str(x10, MemOperand(x11));
-
   // Invoke the function by calling through the JS entry trampoline builtin.
   // Notice that we cannot store a reference to the trampoline code directly in
   // this stub, because runtime stubs are not traversed when doing GC.

src/execution.cc

@@ -99,6 +99,8 @@ MUST_USE_RESULT MaybeHandle<Object> Invoke(Isolate* isolate, bool is_construct,
     SealHandleScope shs(isolate);
     JSEntryFunction stub_entry = FUNCTION_CAST<JSEntryFunction>(code->entry());
 
+    if (FLAG_clear_exceptions_on_js_entry) isolate->clear_pending_exception();
+
     // Call the function through the right JS entry stub.
     Object* orig_func = *new_target;
     Object* func = *target;

src/flag-definitions.h

@@ -767,6 +767,10 @@ DEFINE_BOOL(scavenge_reclaim_unmodified_objects, true,
 DEFINE_INT(heap_growing_percent, 0,
            "specifies heap growing factor as (1 + heap_growing_percent/100)")
 
+// execution.cc, messages.cc
+DEFINE_BOOL(clear_exceptions_on_js_entry, true,
+            "clear pending exceptions when entering JavaScript")
+
 // counters.cc
 DEFINE_INT(histogram_interval, 600000,
            "time interval in ms for aggregating memory histograms")

src/ia32/code-stubs-ia32.cc

@@ -1847,10 +1847,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
   __ bind(&invoke);
   __ PushStackHandler();
 
-  // Clear any pending exceptions.
-  __ mov(edx, Immediate(isolate()->factory()->the_hole_value()));
-  __ mov(Operand::StaticVariable(pending_exception), edx);
-
   // Fake a receiver (NULL).
   __ push(Immediate(0));  // receiver
 

src/messages.cc

@@ -884,10 +884,13 @@ MaybeHandle<Object> ErrorUtils::MakeGenericError(
     Isolate* isolate, Handle<JSFunction> constructor, int template_index,
     Handle<Object> arg0, Handle<Object> arg1, Handle<Object> arg2,
     FrameSkipMode mode) {
-  // This function used to be implemented in JavaScript, and JSEntryStub clears
-  // any pending exceptions - so whenever we'd call this from C++, pending
-  // exceptions would be cleared. Preserve this behavior.
-  isolate->clear_pending_exception();
+  if (FLAG_clear_exceptions_on_js_entry) {
+    // This function used to be implemented in JavaScript, and JSEntryStub
+    // clears
+    // any pending exceptions - so whenever we'd call this from C++, pending
+    // exceptions would be cleared. Preserve this behavior.
+    isolate->clear_pending_exception();
+  }
 
   DCHECK(mode != SKIP_UNTIL_SEEN);
 

src/mips/code-stubs-mips.cc

@@ -1221,12 +1221,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
   // restores all kCalleeSaved registers (including cp and fp) to their
   // saved values before returning a failure to C.
 
-  // Clear any pending exceptions.
-  __ LoadRoot(t1, Heap::kTheHoleValueRootIndex);
-  __ li(t0, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
-                                      isolate)));
-  __ sw(t1, MemOperand(t0));
-
   // Invoke the function by calling through JS entry trampoline builtin.
   // Notice that we cannot store a reference to the trampoline code directly in
   // this stub, because runtime stubs are not traversed when doing GC.

src/mips64/code-stubs-mips64.cc

@@ -1217,12 +1217,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
   // restores all kCalleeSaved registers (including cp and fp) to their
   // saved values before returning a failure to C.
 
-  // Clear any pending exceptions.
-  __ LoadRoot(a5, Heap::kTheHoleValueRootIndex);
-  __ li(a4, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
-                                      isolate)));
-  __ sd(a5, MemOperand(a4));
-
   // Invoke the function by calling through JS entry trampoline builtin.
   // Notice that we cannot store a reference to the trampoline code directly in
   // this stub, because runtime stubs are not traversed when doing GC.

src/x64/code-stubs-x64.cc

@@ -1789,10 +1789,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
   __ bind(&invoke);
   __ PushStackHandler();
 
-  // Clear any pending exceptions.
-  __ LoadRoot(rax, Heap::kTheHoleValueRootIndex);
-  __ Store(pending_exception, rax);
-
   // Fake a receiver (NULL).
   __ Push(Immediate(0));  // receiver