Direct call api functions (arm implementation)

src/arm/macro-assembler-arm.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1379 matching lines @@
   Call(stub->GetCode(), RelocInfo::CODE_TARGET, cond);
 }
 
 
 void MacroAssembler::TailCallStub(CodeStub* stub, Condition cond) {
   ASSERT(allow_stub_calls());  // stub calls are not allowed in some stubs
   Jump(stub->GetCode(), RelocInfo::CODE_TARGET, cond);
 }
 
 
+MaybeObject* MacroAssembler::TryTailCallStub(CodeStub* stub, Condition cond) {
+  ASSERT(allow_stub_calls());  // stub calls are not allowed in some stubs
+  Object* result;
+  { MaybeObject* maybe_result = stub->TryGetCode();
+    if (!maybe_result->ToObject(&result)) return maybe_result;
+  }
+  Jump(stub->GetCode(), RelocInfo::CODE_TARGET, cond);
+  return result;
+}
+
+void MacroAssembler::EnterExitFramePrologue(int unwind_space) {
+  add(ip, sp, Operand(unwind_space * kPointerSize));
+  // Push in reverse order: caller_fp, sp_on_exit, and caller_pc.
+  stm(db_w, sp, fp.bit() | ip.bit() | lr.bit());
+  mov(fp, Operand(sp));
+
+  mov(ip, Operand(CodeObject()));
+  push(ip);
+  mov(ip, Operand(ExitApiFrameConstants::kMarker));
+  push(ip);
+  push(ip);  // Exit Frame sp patched before call.
+
+  mov(ip, Operand(ExternalReference(Top::k_c_entry_fp_address)));
+  str(fp, MemOperand(ip));
+  mov(ip, Operand(ExternalReference(Top::k_context_address)));
+  str(cp, MemOperand(ip));
+}
+
+void MacroAssembler::EnterExitFrameEpilogue(int arg_stack_space) {
+  // Create space for the args.
+  sub(sp, sp, Operand(arg_stack_space * kPointerSize));
+
+  int frame_alignment = ActivationFrameAlignment();
+  int frame_alignment_mask = frame_alignment - 1;
+  if (frame_alignment > kPointerSize) {
+    ASSERT(frame_alignment == 2 * kPointerSize);
+    tst(sp, Operand(frame_alignment_mask));
+    // Stack alignment place holder need not be initialized as its below
+    // c_entry_fp_address and does not affect GC.
+    push(ip, nz);
+  }
+  str(sp, MemOperand(fp, ExitApiFrameConstants::kSPOffset));
+}
+
+void MacroAssembler::PrepareCallApiFunction(int arg_stack_space,
+                                            int unwind_space) {
+  EnterExitFramePrologue(unwind_space);
+  EnterExitFrameEpilogue(arg_stack_space);
+}
+
+static int AddressOffset(ExternalReference ref0, ExternalReference ref1) {
+  int64_t offset = (ref0.address() - ref1.address());
+  // Check that fits into int.
+  ASSERT(static_cast<int>(offset) == offset);
+  return static_cast<int>(offset);
+}
+
+MaybeObject* MacroAssembler::TryCallApiFunctionAndReturn(
+    ApiFunction* function) {
+  ExternalReference next_address =
+      ExternalReference::handle_scope_next_address();
+  const int kNextOffset = 0;
+  const int kLimitOffset = AddressOffset(
+      ExternalReference::handle_scope_limit_address(),
+      next_address);
+  const int kLevelOffset = AddressOffset(
+      ExternalReference::handle_scope_level_address(),
+      next_address);
+
+  // Allocate HandleScope in callee-save registers.
+  mov(r7, Operand(next_address));
+  ldr(r4, MemOperand(r7, kNextOffset));
+  ldr(r5, MemOperand(r7, kLimitOffset));
+  ldr(r6, MemOperand(r7, kLevelOffset));
+  add(r6, r6, Operand(1));
+  str(r6, MemOperand(r7, kLevelOffset));
+
+  // Call the api function.
+  Call(function->address(), RelocInfo::RUNTIME_ENTRY);

[SeRya, 2011/01/18 19:01:57]

This will be translated into
mov(lr, Operand(pc), LeaveCC, cond);
mov(pc, Operand(target), LeaveCC, cond);
(or equivalent with blx).

The register is unreachable for GC which needs to fix the return address if the
code has been moved, isn't it?

Apparently the only way to survive code relocation is to make the lr register to
point to an unmovable piece of code. 

+
+  Label promote_scheduled_exception;
+  Label delete_allocated_handles;
+  Label leave_exit_frame;
+
+  // If result is non-zero, dereference to get the result value
+  // otherwise set it to undefined.
+  cmp(r0, Operand(0));
+  LoadRoot(r0, Heap::kUndefinedValueRootIndex, eq);
+  ldr(r0, MemOperand(r0), ne);
+
+  // No more valid handles (the result handle was the last one). Restore
+  // previous handle scope.
+  str(r4, MemOperand(r7, kNextOffset));
+  if (FLAG_debug_code) {
+    ldr(r1, MemOperand(r7, kLevelOffset));
+    cmp(r1, r6);
+    Check(eq, "Unexpected level after return from api call");
+  }
+  sub(r6, r6, Operand(1));
+  str(r6, MemOperand(r7, kLevelOffset));
+  ldr(ip, MemOperand(r7, kLimitOffset));
+  cmp(r5, ip);
+  b(ne, &delete_allocated_handles);
+
+  // Check if the function scheduled an exception.
+  bind(&leave_exit_frame);
+  LoadRoot(r4, Heap::kTheHoleValueRootIndex);
+  mov(ip, Operand(ExternalReference(Top::k_pending_exception_address)));
+  ldr(r5, MemOperand(ip));
+  cmp(r4, r5);
+  b(ne, &promote_scheduled_exception);
+  LeaveExitFrame(false);
+
+  bind(&promote_scheduled_exception);
+  MaybeObject* result = TryTailCallExternalReference(
+      ExternalReference(Runtime::kPromoteScheduledException), 0, 1);
+  if (result->IsFailure()) {
+    return result;
+  }
+
+  // HandleScope limit has changed. Delete allocated extensions.
+  bind(&delete_allocated_handles);
+  str(r5, MemOperand(r7, kLimitOffset));
+  mov(r4, r0);
+  PrepareCallCFunction(0, r5);
+  CallCFunction(ExternalReference::delete_handle_scope_extensions(), 0);
+  mov(r0, r4);
+  jmp(&leave_exit_frame);
+
+  return result;
+}
+
+
 void MacroAssembler::IllegalOperation(int num_arguments) {
   if (num_arguments > 0) {
     add(sp, sp, Operand(num_arguments * kPointerSize));
   }
   LoadRoot(r0, Heap::kUndefinedValueRootIndex);
 }
 
 
 void MacroAssembler::IndexFromHash(Register hash, Register index) {
   // If the hash field contains an array index pick it out. The assert checks
@@ skipping 232 matching lines @@
                                                int num_arguments,
                                                int result_size) {
   // TODO(1236192): Most runtime routines don't need the number of
   // arguments passed in because it is constant. At some point we
   // should remove this need and make the runtime routine entry code
   // smarter.
   mov(r0, Operand(num_arguments));
   JumpToExternalReference(ext);
 }
 
+MaybeObject* MacroAssembler::TryTailCallExternalReference(
+    const ExternalReference& ext, int num_arguments, int result_size) {
+  // TODO(1236192): Most runtime routines don't need the number of
+  // arguments passed in because it is constant. At some point we
+  // should remove this need and make the runtime routine entry code
+  // smarter.
+  mov(r0, Operand(num_arguments));
+  return TryJumpToExternalReference(ext);
+}
 
 void MacroAssembler::TailCallRuntime(Runtime::FunctionId fid,
                                      int num_arguments,
                                      int result_size) {
   TailCallExternalReference(ExternalReference(fid), num_arguments, result_size);
 }
 
 
 void MacroAssembler::JumpToExternalReference(const ExternalReference& builtin) {
 #if defined(__thumb__)
   // Thumb mode builtin.
   ASSERT((reinterpret_cast<intptr_t>(builtin.address()) & 1) == 1);
 #endif
   mov(r1, Operand(builtin));
   CEntryStub stub(1);
   Jump(stub.GetCode(), RelocInfo::CODE_TARGET);
 }
 
+MaybeObject* MacroAssembler::TryJumpToExternalReference(
+    const ExternalReference& builtin) {
+#if defined(__thumb__)
+  // Thumb mode builtin.
+  ASSERT((reinterpret_cast<intptr_t>(builtin.address()) & 1) == 1);
+#endif
+  mov(r1, Operand(builtin));
+  CEntryStub stub(1);
+  return TryTailCallStub(&stub);
+}
 
 void MacroAssembler::InvokeBuiltin(Builtins::JavaScript id,
                                    InvokeJSFlags flags) {
   GetBuiltinEntry(r2, id);
   if (flags == CALL_JS) {
     Call(r2);
   } else {
     ASSERT(flags == JUMP_JS);
     Jump(r2);
   }
@@ skipping 465 matching lines @@
 
 void CodePatcher::Emit(Address addr) {
   masm()->emit(reinterpret_cast<Instr>(addr));
 }
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM