Return Object* instead of MaybeObject* from runtime calls.

src/arm64/code-stubs-arm64.cc

Index: src/arm64/code-stubs-arm64.cc
diff --git a/src/arm64/code-stubs-arm64.cc b/src/arm64/code-stubs-arm64.cc
index a42f5cd34da87677a2f8fd4d59c417c82fbb4ee5..61339e2cb4b8f78507b16b26effdc1f65155b28a 100644
--- a/src/arm64/code-stubs-arm64.cc
+++ b/src/arm64/code-stubs-arm64.cc
@@ -1477,15 +1477,78 @@ void CEntryStub::GenerateAheadOfTime(Isolate* isolate) {
 }
 
 
-void CEntryStub::GenerateCore(MacroAssembler* masm,
-                              Label* throw_normal,
-                              Label* throw_termination,
-                              bool do_gc,
-                              bool always_allocate) {
-  // x0  : Result parameter for PerformGC, if do_gc is true.
+void CEntryStub::Generate(MacroAssembler* masm) {
+  // The Abort mechanism relies on CallRuntime, which in turn relies on
+  // CEntryStub, so until this stub has been generated, we have to use a
+  // fall-back Abort mechanism.
+  //
+  // Note that this stub must be generated before any use of Abort.
+  MacroAssembler::NoUseRealAbortsScope no_use_real_aborts(masm);
+
+  ASM_LOCATION("CEntryStub::Generate entry");
+  ProfileEntryHookStub::MaybeCallEntryHook(masm);
+
+  // Register parameters:
+  //    x0: argc (including receiver, untagged)
+  //    x1: target
+  //
+  // The stack on entry holds the arguments and the receiver, with the receiver
+  // at the highest address:
+  //
+  //    jssp]argc-1]: receiver
+  //    jssp[argc-2]: arg[argc-2]
+  //    ...           ...
+  //    jssp[1]:      arg[1]
+  //    jssp[0]:      arg[0]
+  //
+  // The arguments are in reverse order, so that arg[argc-2] is actually the
+  // first argument to the target function and arg[0] is the last.
+  ASSERT(jssp.Is(__ StackPointer()));
+  const Register& argc_input = x0;
+  const Register& target_input = x1;
+
+  // Calculate argv, argc and the target address, and store them in
+  // callee-saved registers so we can retry the call without having to reload
+  // these arguments.
+  // TODO(jbramley): If the first call attempt succeeds in the common case (as

[Yang, 2014/04/22 11:28:55]

@jbramley: now that we don't have a retry loop anymore, this should be doable. I
made a modest attempt, but for some reason it didn't work out, and I punted on
this. Maybe you want to have a go at this?

[jbramley, 2014/04/22 11:37:03]

Yep, I'll have a look. We're gradually working through TODOs in the arm64 port
so they'll all get looked at eventually.

+  // it should), then we might be better off putting these parameters directly
+  // into their argument registers, rather than using callee-saved registers and
+  // preserving them on the stack.
+  const Register& argv = x21;
+  const Register& argc = x22;
+  const Register& target = x23;
+
+  // Derive argv from the stack pointer so that it points to the first argument
+  // (arg[argc-2]), or just below the receiver in case there are no arguments.
+  //  - Adjust for the arg[] array.
+  Register temp_argv = x11;
+  __ Add(temp_argv, jssp, Operand(x0, LSL, kPointerSizeLog2));
+  //  - Adjust for the receiver.
+  __ Sub(temp_argv, temp_argv, 1 * kPointerSize);
+
+  // Enter the exit frame. Reserve three slots to preserve x21-x23 callee-saved
+  // registers.
+  FrameScope scope(masm, StackFrame::MANUAL);
+  __ EnterExitFrame(save_doubles_, x10, 3);
+  ASSERT(csp.Is(__ StackPointer()));
+
+  // Poke callee-saved registers into reserved space.
+  __ Poke(argv, 1 * kPointerSize);
+  __ Poke(argc, 2 * kPointerSize);
+  __ Poke(target, 3 * kPointerSize);
+
+  // We normally only keep tagged values in callee-saved registers, as they
+  // could be pushed onto the stack by called stubs and functions, and on the
+  // stack they can confuse the GC. However, we're only calling C functions
+  // which can push arbitrary data onto the stack anyway, and so the GC won't
+  // examine that part of the stack.
+  __ Mov(argc, argc_input);
+  __ Mov(target, target_input);
+  __ Mov(argv, temp_argv);
+
   // x21 : argv
   // x22 : argc
-  // x23 : target
+  // x23 : call target
   //
   // The stack (on entry) holds the arguments and the receiver, with the
   // receiver at the highest address:
@@ -1517,42 +1580,20 @@ void CEntryStub::GenerateCore(MacroAssembler* masm,
   // untouched, and the stub either throws an exception by jumping to one of
   // the provided throw_ labels, or it falls through. The failure details are
   // passed through in x0.
+
   ASSERT(csp.Is(__ StackPointer()));
 
   Isolate* isolate = masm->isolate();
 
-  const Register& argv = x21;
-  const Register& argc = x22;
-  const Register& target = x23;
-
-  if (do_gc) {
-    // Call Runtime::PerformGC, passing x0 (the result parameter for
-    // PerformGC) and x1 (the isolate).
-    __ Mov(x1, ExternalReference::isolate_address(masm->isolate()));
-    __ CallCFunction(
-        ExternalReference::perform_gc_function(isolate), 2, 0);
-  }
-
-  ExternalReference scope_depth =
-      ExternalReference::heap_always_allocate_scope_depth(isolate);
-  if (always_allocate) {
-    __ Mov(x10, Operand(scope_depth));
-    __ Ldr(x11, MemOperand(x10));
-    __ Add(x11, x11, 1);
-    __ Str(x11, MemOperand(x10));
-  }
-
   // Prepare AAPCS64 arguments to pass to the builtin.
   __ Mov(x0, argc);
   __ Mov(x1, argv);
   __ Mov(x2, ExternalReference::isolate_address(isolate));
 
-  // Store the return address on the stack, in the space previously allocated
-  // by EnterExitFrame. The return address is queried by
-  // ExitFrame::GetStateForFramePointer.
   Label return_location;
   __ Adr(x12, &return_location);
   __ Poke(x12, 0);
+
   if (__ emit_debug_code()) {
     // Verify that the slot below fp[kSPOffset]-8 points to the return location
     // (currently in x12).
@@ -1567,27 +1608,16 @@ void CEntryStub::GenerateCore(MacroAssembler* masm,
   // Call the builtin.
   __ Blr(target);
   __ Bind(&return_location);
-  const Register& result = x0;
-
-  if (always_allocate) {
-    __ Mov(x10, Operand(scope_depth));
-    __ Ldr(x11, MemOperand(x10));
-    __ Sub(x11, x11, 1);
-    __ Str(x11, MemOperand(x10));
-  }
 
   //  x0    result      The return code from the call.
   //  x21   argv
   //  x22   argc
   //  x23   target
-  //
-  // If all of the result bits matching kFailureTagMask are '1', the result is
-  // a failure. Otherwise, it's an ordinary tagged object and the call was a
-  // success.
-  Label failure;
-  __ And(x10, result, kFailureTagMask);
-  __ Cmp(x10, kFailureTagMask);
-  __ B(&failure, eq);
+  const Register& result = x0;
+
+  Label failure_returned;
+  __ CompareRoot(result, Heap::kExceptionRootIndex);
+  __ B(eq, &failure_returned);
 
   // The call succeeded, so unwind the stack and return.
 
@@ -1612,27 +1642,16 @@ void CEntryStub::GenerateCore(MacroAssembler* masm,
   // hasn't changed (except for the return address).
   __ SetStackPointer(csp);
 
-  __ Bind(&failure);
+  __ Bind(&failure_returned);
   // The call failed, so check if we need to throw an exception, and fall
   // through (to retry) otherwise.
 
-  Label retry;
-  //  x0    result      The return code from the call, including the failure
-  //                    code and details.
-  //  x21   argv
-  //  x22   argc
-  //  x23   target
-  // Refer to the Failure class for details of the bit layout.
-  STATIC_ASSERT(Failure::RETRY_AFTER_GC == 0);
-  __ Tst(result, kFailureTypeTagMask << kFailureTagSize);
-  __ B(eq, &retry);   // RETRY_AFTER_GC
+  ExternalReference pending_exception_address(
+      Isolate::kPendingExceptionAddress, isolate);
 
-  // Retrieve the pending exception.
   const Register& exception = result;
   const Register& exception_address = x11;
-  __ Mov(exception_address,
-         Operand(ExternalReference(Isolate::kPendingExceptionAddress,
-                                   isolate)));
+  __ Mov(exception_address, Operand(pending_exception_address));
   __ Ldr(exception, MemOperand(exception_address));
 
   // Clear the pending exception.
@@ -1646,118 +1665,9 @@ void CEntryStub::GenerateCore(MacroAssembler* masm,
 
   // Special handling of termination exceptions, which are uncatchable by
   // JavaScript code.
+  Label throw_termination_exception;
   __ Cmp(exception, Operand(isolate->factory()->termination_exception()));
-  __ B(eq, throw_termination);
-
-  // Handle normal exception.
-  __ B(throw_normal);
-
-  __ Bind(&retry);
-  // The result (x0) is passed through as the next PerformGC parameter.
-}
-
-
-void CEntryStub::Generate(MacroAssembler* masm) {
-  // The Abort mechanism relies on CallRuntime, which in turn relies on
-  // CEntryStub, so until this stub has been generated, we have to use a
-  // fall-back Abort mechanism.
-  //
-  // Note that this stub must be generated before any use of Abort.
-  MacroAssembler::NoUseRealAbortsScope no_use_real_aborts(masm);
-
-  ASM_LOCATION("CEntryStub::Generate entry");
-  ProfileEntryHookStub::MaybeCallEntryHook(masm);
-
-  // Register parameters:
-  //    x0: argc (including receiver, untagged)
-  //    x1: target
-  //
-  // The stack on entry holds the arguments and the receiver, with the receiver
-  // at the highest address:
-  //
-  //    jssp]argc-1]: receiver
-  //    jssp[argc-2]: arg[argc-2]
-  //    ...           ...
-  //    jssp[1]:      arg[1]
-  //    jssp[0]:      arg[0]
-  //
-  // The arguments are in reverse order, so that arg[argc-2] is actually the
-  // first argument to the target function and arg[0] is the last.
-  ASSERT(jssp.Is(__ StackPointer()));
-  const Register& argc_input = x0;
-  const Register& target_input = x1;
-
-  // Calculate argv, argc and the target address, and store them in
-  // callee-saved registers so we can retry the call without having to reload
-  // these arguments.
-  // TODO(jbramley): If the first call attempt succeeds in the common case (as
-  // it should), then we might be better off putting these parameters directly
-  // into their argument registers, rather than using callee-saved registers and
-  // preserving them on the stack.
-  const Register& argv = x21;
-  const Register& argc = x22;
-  const Register& target = x23;
-
-  // Derive argv from the stack pointer so that it points to the first argument
-  // (arg[argc-2]), or just below the receiver in case there are no arguments.
-  //  - Adjust for the arg[] array.
-  Register temp_argv = x11;
-  __ Add(temp_argv, jssp, Operand(x0, LSL, kPointerSizeLog2));
-  //  - Adjust for the receiver.
-  __ Sub(temp_argv, temp_argv, 1 * kPointerSize);
-
-  // Enter the exit frame. Reserve three slots to preserve x21-x23 callee-saved
-  // registers.
-  FrameScope scope(masm, StackFrame::MANUAL);
-  __ EnterExitFrame(save_doubles_, x10, 3);
-  ASSERT(csp.Is(__ StackPointer()));
-
-  // Poke callee-saved registers into reserved space.
-  __ Poke(argv, 1 * kPointerSize);
-  __ Poke(argc, 2 * kPointerSize);
-  __ Poke(target, 3 * kPointerSize);
-
-  // We normally only keep tagged values in callee-saved registers, as they
-  // could be pushed onto the stack by called stubs and functions, and on the
-  // stack they can confuse the GC. However, we're only calling C functions
-  // which can push arbitrary data onto the stack anyway, and so the GC won't
-  // examine that part of the stack.
-  __ Mov(argc, argc_input);
-  __ Mov(target, target_input);
-  __ Mov(argv, temp_argv);
-
-  Label throw_normal;
-  Label throw_termination;
-
-  // Call the runtime function.
-  GenerateCore(masm,
-               &throw_normal,
-               &throw_termination,
-               false,
-               false);
-
-  // If successful, the previous GenerateCore will have returned to the
-  // calling code. Otherwise, we fall through into the following.
-
-  // Do space-specific GC and retry runtime call.
-  GenerateCore(masm,
-               &throw_normal,
-               &throw_termination,
-               true,
-               false);
-
-  // Do full GC and retry runtime call one final time.
-  __ Mov(x0, reinterpret_cast<uint64_t>(Failure::InternalError()));
-  GenerateCore(masm,
-               &throw_normal,
-               &throw_termination,
-               true,
-               true);
-
-  { FrameScope scope(masm, StackFrame::MANUAL);
-    __ CallCFunction(
-        ExternalReference::out_of_memory_function(masm->isolate()), 0);
-  }
+  __ B(eq, &throw_termination_exception);
 
   // We didn't execute a return case, so the stack frame hasn't been updated
   // (except for the return address slot). However, we don't need to initialize
@@ -1765,24 +1675,18 @@ void CEntryStub::Generate(MacroAssembler* masm) {
   // unwinds the stack.
   __ SetStackPointer(jssp);
 
-  // Throw exceptions.
-  // If we throw an exception, we can end up re-entering CEntryStub before we
-  // pop the exit frame, so need to ensure that x21-x23 contain GC-safe values
-  // here.
-
-  __ Bind(&throw_termination);
-  ASM_LOCATION("Throw termination");
+  ASM_LOCATION("Throw normal");
   __ Mov(argv, 0);
   __ Mov(argc, 0);
   __ Mov(target, 0);
-  __ ThrowUncatchable(x0, x10, x11, x12, x13);
+  __ Throw(x0, x10, x11, x12, x13);
 
-  __ Bind(&throw_normal);
-  ASM_LOCATION("Throw normal");
+  __ Bind(&throw_termination_exception);
+  ASM_LOCATION("Throw termination");
   __ Mov(argv, 0);
   __ Mov(argc, 0);
   __ Mov(target, 0);
-  __ Throw(x0, x10, x11, x12, x13);
+  __ ThrowUncatchable(x0, x10, x11, x12, x13);
 }
 
 
@@ -1882,7 +1786,7 @@ void JSEntryStub::GenerateBody(MacroAssembler* masm, bool is_construct) {
            isolate)));
   }
   __ Str(code_entry, MemOperand(x10));
-  __ Mov(x0, Operand(reinterpret_cast<int64_t>(Failure::Exception())));
+  __ LoadRoot(x0, Heap::kExceptionRootIndex);
   __ B(&exit);
 
   // Invoke: Link this frame into the handler chain.  There's only one