v8/src/x64/stub-cache-x64.cc

// Copyright 2009 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
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


#include "v8.h"

#include "ic-inl.h"
#include "codegen-inl.h"
#include "stub-cache.h"
#include "macro-assembler-x64.h"

namespace v8 {
namespace internal {

#define __ ACCESS_MASM((masm()))


Object* CallStubCompiler::CompileCallConstant(Object* object,
                                              JSObject* holder,
                                              JSFunction* function,
                                              String* name,
                                              StubCompiler::CheckType check) {
  // ----------- S t a t e -------------
  // -----------------------------------
  // rsp[0] return address
  // rsp[8] argument argc
  // rsp[16] argument argc - 1
  // ...
  // rsp[argc * 8] argument 1
  // rsp[(argc + 1) * 8] argument 0 = reciever
  // rsp[(argc + 2) * 8] function name

  Label miss;

  // Get the receiver from the stack.
  const int argc = arguments().immediate();
  __ movq(rdx, Operand(rsp, (argc + 1) * kPointerSize));

  // Check that the receiver isn't a smi.
  if (check != NUMBER_CHECK) {
    __ testl(rdx, Immediate(kSmiTagMask));
    __ j(zero, &miss);
  }

  // Make sure that it's okay not to patch the on stack receiver
  // unless we're doing a receiver map check.
  ASSERT(!object->IsGlobalObject() || check == RECEIVER_MAP_CHECK);

  switch (check) {
    case RECEIVER_MAP_CHECK:
      // Check that the maps haven't changed.
      CheckPrototypes(JSObject::cast(object), rdx, holder,
                      rbx, rcx, name, &miss);

      // Patch the receiver on the stack with the global proxy if
      // necessary.
      if (object->IsGlobalObject()) {
        __ movq(rdx, FieldOperand(rdx, GlobalObject::kGlobalReceiverOffset));
        __ movq(Operand(rsp, (argc + 1) * kPointerSize), rdx);
      }
      break;

    case STRING_CHECK:
      // Check that the object is a two-byte string or a symbol.
      __ CmpObjectType(rdx, FIRST_NONSTRING_TYPE, rcx);
      __ j(above_equal, &miss);
      // Check that the maps starting from the prototype haven't changed.
      GenerateLoadGlobalFunctionPrototype(masm(),
                                          Context::STRING_FUNCTION_INDEX,
                                          rcx);
      CheckPrototypes(JSObject::cast(object->GetPrototype()), rcx, holder,
                      rbx, rdx, name, &miss);
      break;

    case NUMBER_CHECK: {
      Label fast;
      // Check that the object is a smi or a heap number.
      __ testl(rdx, Immediate(kSmiTagMask));
      __ j(zero, &fast);
      __ CmpObjectType(rdx, HEAP_NUMBER_TYPE, rcx);
      __ j(not_equal, &miss);
      __ bind(&fast);
      // Check that the maps starting from the prototype haven't changed.
      GenerateLoadGlobalFunctionPrototype(masm(),
                                          Context::NUMBER_FUNCTION_INDEX,
                                          rcx);
      CheckPrototypes(JSObject::cast(object->GetPrototype()), rcx, holder,
                      rbx, rdx, name, &miss);
      break;
    }

    case BOOLEAN_CHECK: {
      Label fast;
      // Check that the object is a boolean.
      __ Cmp(rdx, Factory::true_value());
      __ j(equal, &fast);
      __ Cmp(rdx, Factory::false_value());
      __ j(not_equal, &miss);
      __ bind(&fast);
      // Check that the maps starting from the prototype haven't changed.
      GenerateLoadGlobalFunctionPrototype(masm(),
                                          Context::BOOLEAN_FUNCTION_INDEX,
                                          rcx);
      CheckPrototypes(JSObject::cast(object->GetPrototype()), rcx, holder,
                      rbx, rdx, name, &miss);
      break;
    }

    case JSARRAY_HAS_FAST_ELEMENTS_CHECK:
      CheckPrototypes(JSObject::cast(object), rdx, holder,
                      rbx, rcx, name, &miss);
      // Make sure object->elements()->map() != Heap::dictionary_array_map()
      // Get the elements array of the object.
      __ movq(rbx, FieldOperand(rdx, JSObject::kElementsOffset));
      // Check that the object is in fast mode (not dictionary).
      __ Cmp(FieldOperand(rbx, HeapObject::kMapOffset),
             Factory::hash_table_map());
      __ j(equal, &miss);
      break;

    default:
      UNREACHABLE();
  }

  // Get the function and setup the context.
  __ Move(rdi, Handle<JSFunction>(function));
  __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));

  // Jump to the cached code (tail call).
  ASSERT(function->is_compiled());
  Handle<Code> code(function->code());
  ParameterCount expected(function->shared()->formal_parameter_count());
  __ InvokeCode(code, expected, arguments(),
                RelocInfo::CODE_TARGET, JUMP_FUNCTION);

  // Handle call cache miss.
  __ bind(&miss);
  Handle<Code> ic = ComputeCallMiss(arguments().immediate());
  __ Jump(ic, RelocInfo::CODE_TARGET);

  // Return the generated code.
  String* function_name = NULL;
  if (function->shared()->name()->IsString()) {
    function_name = String::cast(function->shared()->name());
  }
  return GetCode(CONSTANT_FUNCTION, function_name);
}


Object* CallStubCompiler::CompileCallField(Object* object,
                                           JSObject* holder,
                                           int index,
                                           String* name) {
  // ----------- S t a t e -------------
  // -----------------------------------
  // rsp[0] return address
  // rsp[8] argument argc
  // rsp[16] argument argc - 1
  // ...
  // rsp[argc * 8] argument 1
  // rsp[(argc + 1) * 8] argument 0 = receiver
  // rsp[(argc + 2) * 8] function name
  Label miss;

  // Get the receiver from the stack.
  const int argc = arguments().immediate();
  __ movq(rdx, Operand(rsp, (argc + 1) * kPointerSize));

  // Check that the receiver isn't a smi.
  __ testl(rdx, Immediate(kSmiTagMask));
  __ j(zero, &miss);

  // Do the right check and compute the holder register.
  Register reg =
      CheckPrototypes(JSObject::cast(object), rdx, holder,
                      rbx, rcx, name, &miss);

  GenerateFastPropertyLoad(masm(), rdi, reg, holder, index);

  // Check that the function really is a function.
  __ testl(rdi, Immediate(kSmiTagMask));
  __ j(zero, &miss);
  __ CmpObjectType(rdi, JS_FUNCTION_TYPE, rbx);
  __ j(not_equal, &miss);

  // Patch the receiver on the stack with the global proxy if
  // necessary.
  if (object->IsGlobalObject()) {
    __ movq(rdx, FieldOperand(rdx, GlobalObject::kGlobalReceiverOffset));
    __ movq(Operand(rsp, (argc + 1) * kPointerSize), rdx);
  }

  // Invoke the function.
  __ InvokeFunction(rdi, arguments(), JUMP_FUNCTION);

  // Handle call cache miss.
  __ bind(&miss);
  Handle<Code> ic = ComputeCallMiss(arguments().immediate());
  __ Jump(ic, RelocInfo::CODE_TARGET);

  // Return the generated code.
  return GetCode(FIELD, name);
}


Object* CallStubCompiler::CompileCallInterceptor(Object* a,
                                                 JSObject* b,
                                                 String* c) {
  // TODO(X64): Implement a real stub.
  return Failure::InternalError();
}



Object* CallStubCompiler::CompileCallGlobal(JSObject* object,
                                            GlobalObject* holder,
                                            JSGlobalPropertyCell* cell,
                                            JSFunction* function,
                                            String* name) {
  // ----------- S t a t e -------------
  // -----------------------------------
  // rsp[0] return address
  // rsp[8] argument argc
  // rsp[16] argument argc - 1
  // ...
  // rsp[argc * 8] argument 1
  // rsp[(argc + 1) * 8] argument 0 = receiver
  // rsp[(argc + 2) * 8] function name
  Label miss;

  __ IncrementCounter(&Counters::call_global_inline, 1);

  // Get the number of arguments.
  const int argc = arguments().immediate();

  // Get the receiver from the stack.
  __ movq(rdx, Operand(rsp, (argc + 1) * kPointerSize));

  // If the object is the holder then we know that it's a global
  // object which can only happen for contextual calls. In this case,
  // the receiver cannot be a smi.
  if (object != holder) {
    __ testl(rdx, Immediate(kSmiTagMask));
    __ j(zero, &miss);
  }

  // Check that the maps haven't changed.
  CheckPrototypes(object, rdx, holder, rbx, rcx, name, &miss);

  // Get the value from the cell.
  __ Move(rdi, Handle<JSGlobalPropertyCell>(cell));
  __ movq(rdi, FieldOperand(rdi, JSGlobalPropertyCell::kValueOffset));

  // Check that the cell contains the same function.
  __ Cmp(rdi, Handle<JSFunction>(function));
  __ j(not_equal, &miss);

  // Patch the receiver on the stack with the global proxy.
  if (object->IsGlobalObject()) {
    __ movq(rdx, FieldOperand(rdx, GlobalObject::kGlobalReceiverOffset));
    __ movq(Operand(rsp, (argc + 1) * kPointerSize), rdx);
  }

  // Setup the context (function already in edi).
  __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));

  // Jump to the cached code (tail call).
  ASSERT(function->is_compiled());
  Handle<Code> code(function->code());
  ParameterCount expected(function->shared()->formal_parameter_count());
  __ InvokeCode(code, expected, arguments(),
                RelocInfo::CODE_TARGET, JUMP_FUNCTION);

  // Handle call cache miss.
  __ bind(&miss);
  __ DecrementCounter(&Counters::call_global_inline, 1);
  __ IncrementCounter(&Counters::call_global_inline_miss, 1);
  Handle<Code> ic = ComputeCallMiss(arguments().immediate());
  __ Jump(ic, RelocInfo::CODE_TARGET);

  // Return the generated code.
  return GetCode(NORMAL, name);
}


Object* LoadStubCompiler::CompileLoadCallback(JSObject* a,
                                              JSObject* b,
                                              AccessorInfo* c,
                                              String* d) {
  // TODO(X64): Implement a real stub.
  return Failure::InternalError();
}


Object* LoadStubCompiler::CompileLoadConstant(JSObject* object,
                                              JSObject* holder,
                                              Object* value,
                                              String* name) {
  // ----------- S t a t e -------------
  //  -- rcx    : name
  //  -- rsp[0] : return address
  //  -- rsp[8] : receiver
  // -----------------------------------
  Label miss;

  __ movq(rax, (Operand(rsp, kPointerSize)));
  GenerateLoadConstant(object, holder, rax, rbx, rdx, value, name, &miss);
  __ bind(&miss);
  GenerateLoadMiss(masm(), Code::LOAD_IC);

  // Return the generated code.
  return GetCode(CONSTANT_FUNCTION, name);
}


Object* LoadStubCompiler::CompileLoadField(JSObject* object,
                                           JSObject* holder,
                                           int index,
                                           String* name) {
  // ----------- S t a t e -------------
  //  -- rcx    : name
  //  -- rsp[0] : return address
  //  -- rsp[8] : receiver
  // -----------------------------------
  Label miss;

  __ movq(rax, (Operand(rsp, kPointerSize)));
  GenerateLoadField(object, holder, rax, rbx, rdx, index, name, &miss);
  __ bind(&miss);
  GenerateLoadMiss(masm(), Code::LOAD_IC);

  // Return the generated code.
  return GetCode(FIELD, name);
}


Object* LoadStubCompiler::CompileLoadInterceptor(JSObject* a,
                                                 JSObject* b,
                                                 String* c) {
  // TODO(X64): Implement a real stub.
  return Failure::InternalError();
}


Object* LoadStubCompiler::CompileLoadGlobal(JSObject* object,
                                            GlobalObject* holder,
                                            JSGlobalPropertyCell* cell,
                                            String* name,
                                            bool is_dont_delete) {
  // ----------- S t a t e -------------
  //  -- rcx    : name
  //  -- rsp[0] : return address
  //  -- rsp[8] : receiver
  // -----------------------------------
  Label miss;

  __ IncrementCounter(&Counters::named_load_global_inline, 1);

  // Get the receiver from the stack.
  __ movq(rax, (Operand(rsp, kPointerSize)));

  // If the object is the holder then we know that it's a global
  // object which can only happen for contextual loads. In this case,
  // the receiver cannot be a smi.
  if (object != holder) {
    __ testl(rax, Immediate(kSmiTagMask));
    __ j(zero, &miss);
  }

  // Check that the maps haven't changed.
  CheckPrototypes(object, rax, holder, rbx, rdx, name, &miss);

  // Get the value from the cell.
  __ Move(rax, Handle<JSGlobalPropertyCell>(cell));
  __ movq(rax, FieldOperand(rax, JSGlobalPropertyCell::kValueOffset));

  // Check for deleted property if property can actually be deleted.
  if (!is_dont_delete) {
    __ Cmp(rax, Factory::the_hole_value());
    __ j(equal, &miss);
  } else if (FLAG_debug_code) {
    __ Cmp(rax, Factory::the_hole_value());
    __ Check(not_equal, "DontDelete cells can't contain the hole");
  }

  __ ret(0);

  __ bind(&miss);
  __ DecrementCounter(&Counters::named_load_global_inline, 1);
  __ IncrementCounter(&Counters::named_load_global_inline_miss, 1);
  GenerateLoadMiss(masm(), Code::LOAD_IC);

  // Return the generated code.
  return GetCode(NORMAL, name);
}


Object* StoreStubCompiler::CompileStoreCallback(JSObject* a,
                                                AccessorInfo* b,
                                                String* c) {
  UNIMPLEMENTED();
  return NULL;
}


Object* StoreStubCompiler::CompileStoreField(JSObject* a,
                                             int b,
                                             Map* c,
                                             String* d) {
  UNIMPLEMENTED();
  return NULL;
}


Object* StoreStubCompiler::CompileStoreInterceptor(JSObject* a, String* b) {
  UNIMPLEMENTED();
  return NULL;
}


Object* StoreStubCompiler::CompileStoreGlobal(GlobalObject* object,
                                              JSGlobalPropertyCell* cell,
                                              String* name) {
  UNIMPLEMENTED();
  return NULL;
}


// TODO(1241006): Avoid having lazy compile stubs specialized by the
// number of arguments. It is not needed anymore.
Object* StubCompiler::CompileLazyCompile(Code::Flags flags) {
  // Enter an internal frame.
  __ EnterInternalFrame();

  // Push a copy of the function onto the stack.
  __ push(rdi);

  __ push(rdi);  // function is also the parameter to the runtime call
  __ CallRuntime(Runtime::kLazyCompile, 1);
  __ pop(rdi);

  // Tear down temporary frame.
  __ LeaveInternalFrame();

  // Do a tail-call of the compiled function.
  __ lea(rcx, FieldOperand(rax, Code::kHeaderSize));
  __ jmp(rcx);

  return GetCodeWithFlags(flags, "LazyCompileStub");
}


Register StubCompiler::CheckPrototypes(JSObject* object,
                                       Register object_reg,
                                       JSObject* holder,
                                       Register holder_reg,
                                       Register scratch,
                                       String* name,
                                       Label* miss) {
  // Check that the maps haven't changed.
  Register result =
      __ CheckMaps(object, object_reg, holder, holder_reg, scratch, miss);

  // If we've skipped any global objects, it's not enough to verify
  // that their maps haven't changed.
  while (object != holder) {
    if (object->IsGlobalObject()) {
      GlobalObject* global = GlobalObject::cast(object);
      Object* probe = global->EnsurePropertyCell(name);
      if (probe->IsFailure()) {
        set_failure(Failure::cast(probe));
        return result;
      }
      JSGlobalPropertyCell* cell = JSGlobalPropertyCell::cast(probe);
      ASSERT(cell->value()->IsTheHole());
      __ Move(scratch, Handle<Object>(cell));
      __ Cmp(FieldOperand(scratch, JSGlobalPropertyCell::kValueOffset),
             Factory::the_hole_value());
      __ j(not_equal, miss);
    }
    object = JSObject::cast(object->GetPrototype());
  }

  // Return the register containing the holder.
  return result;
}


void StubCompiler::GenerateLoadField(JSObject* object,
                                     JSObject* holder,
                                     Register receiver,
                                     Register scratch1,
                                     Register scratch2,
                                     int index,
                                     String* name,
                                     Label* miss) {
  // Check that the receiver isn't a smi.
  __ testl(receiver, Immediate(kSmiTagMask));
  __ j(zero, miss);

  // Check the prototype chain.
  Register reg =
      CheckPrototypes(object, receiver, holder,
                      scratch1, scratch2, name, miss);

  // Get the value from the properties.
  GenerateFastPropertyLoad(masm(), rax, reg, holder, index);
  __ ret(0);
}


void StubCompiler::GenerateLoadConstant(JSObject* object,
                                        JSObject* holder,
                                        Register receiver,
                                        Register scratch1,
                                        Register scratch2,
                                        Object* value,
                                        String* name,
                                        Label* miss) {
  // Check that the receiver isn't a smi.
  __ testl(receiver, Immediate(kSmiTagMask));
  __ j(zero, miss);

  // Check that the maps haven't changed.
  Register reg =
      CheckPrototypes(object, receiver, holder,
                      scratch1, scratch2, name, miss);

  // Return the constant value.
  __ Move(rax, Handle<Object>(value));
  __ ret(0);
}


#undef __

//-----------------------------------------------------------------------------
// StubCompiler static helper functions

#define __ ACCESS_MASM(masm)


static void ProbeTable(MacroAssembler* masm,
                       Code::Flags flags,
                       StubCache::Table table,
                       Register name,
                       Register offset) {
  ExternalReference key_offset(SCTableReference::keyReference(table));
  Label miss;

  __ movq(kScratchRegister, key_offset);
  // Check that the key in the entry matches the name.
  __ cmpl(name, Operand(kScratchRegister, offset, times_4, 0));
  __ j(not_equal, &miss);
  // Get the code entry from the cache.
  // Use key_offset + kPointerSize, rather than loading value_offset.
  __ movq(kScratchRegister,
          Operand(kScratchRegister, offset, times_4, kPointerSize));
  // Check that the flags match what we're looking for.
  __ movl(offset, FieldOperand(kScratchRegister, Code::kFlagsOffset));
  __ and_(offset, Immediate(~Code::kFlagsNotUsedInLookup));
  __ cmpl(offset, Immediate(flags));
  __ j(not_equal, &miss);

  // Jump to the first instruction in the code stub.
  __ addq(kScratchRegister, Immediate(Code::kHeaderSize - kHeapObjectTag));
  __ jmp(kScratchRegister);

  __ bind(&miss);
}


void StubCompiler::GenerateLoadMiss(MacroAssembler* masm, Code::Kind kind) {
  ASSERT(kind == Code::LOAD_IC || kind == Code::KEYED_LOAD_IC);
  Code* code = NULL;
  if (kind == Code::LOAD_IC) {
    code = Builtins::builtin(Builtins::LoadIC_Miss);
  } else {
    code = Builtins::builtin(Builtins::KeyedLoadIC_Miss);
  }

  Handle<Code> ic(code);
  __ Jump(ic, RelocInfo::CODE_TARGET);
}


void StubCompiler::GenerateLoadGlobalFunctionPrototype(MacroAssembler* masm,
                                                       int index,
                                                       Register prototype) {
  // Load the global or builtins object from the current context.
  __ movq(prototype,
             Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
  // Load the global context from the global or builtins object.
  __ movq(prototype,
             FieldOperand(prototype, GlobalObject::kGlobalContextOffset));
  // Load the function from the global context.
  __ movq(prototype, Operand(prototype, Context::SlotOffset(index)));
  // Load the initial map.  The global functions all have initial maps.
  __ movq(prototype,
             FieldOperand(prototype, JSFunction::kPrototypeOrInitialMapOffset));
  // Load the prototype from the initial map.
  __ movq(prototype, FieldOperand(prototype, Map::kPrototypeOffset));
}


// Load a fast property out of a holder object (src). In-object properties
// are loaded directly otherwise the property is loaded from the properties
// fixed array.
void StubCompiler::GenerateFastPropertyLoad(MacroAssembler* masm,
                                            Register dst, Register src,
                                            JSObject* holder, int index) {
  // Adjust for the number of properties stored in the holder.
  index -= holder->map()->inobject_properties();
  if (index < 0) {
    // Get the property straight out of the holder.
    int offset = holder->map()->instance_size() + (index * kPointerSize);
    __ movq(dst, FieldOperand(src, offset));
  } else {
    // Calculate the offset into the properties array.
    int offset = index * kPointerSize + FixedArray::kHeaderSize;
    __ movq(dst, FieldOperand(src, JSObject::kPropertiesOffset));
    __ movq(dst, FieldOperand(dst, offset));
  }
}


void StubCache::GenerateProbe(MacroAssembler* masm,
                              Code::Flags flags,
                              Register receiver,
                              Register name,
                              Register scratch,
                              Register extra) {
  Label miss;
  USE(extra);  // The register extra is not used on the X64 platform.
  // Make sure that code is valid. The shifting code relies on the
  // entry size being 16.
  ASSERT(sizeof(Entry) == 16);

  // Make sure the flags do not name a specific type.
  ASSERT(Code::ExtractTypeFromFlags(flags) == 0);

  // Make sure that there are no register conflicts.
  ASSERT(!scratch.is(receiver));
  ASSERT(!scratch.is(name));

  // Check that the receiver isn't a smi.
  __ testl(receiver, Immediate(kSmiTagMask));
  __ j(zero, &miss);

  // Get the map of the receiver and compute the hash.
  __ movl(scratch, FieldOperand(name, String::kLengthOffset));
  // Use only the low 32 bits of the map pointer.
  __ addl(scratch, FieldOperand(receiver, HeapObject::kMapOffset));
  __ xor_(scratch, Immediate(flags));
  __ and_(scratch, Immediate((kPrimaryTableSize - 1) << kHeapObjectTagSize));

  // Probe the primary table.
  ProbeTable(masm, flags, kPrimary, name, scratch);

  // Primary miss: Compute hash for secondary probe.
  __ movl(scratch, FieldOperand(name, String::kLengthOffset));
  __ addl(scratch, FieldOperand(receiver, HeapObject::kMapOffset));
  __ xor_(scratch, Immediate(flags));
  __ and_(scratch, Immediate((kPrimaryTableSize - 1) << kHeapObjectTagSize));
  __ subl(scratch, name);
  __ addl(scratch, Immediate(flags));
  __ and_(scratch, Immediate((kSecondaryTableSize - 1) << kHeapObjectTagSize));

  // Probe the secondary table.
  ProbeTable(masm, flags, kSecondary, name, scratch);

  // Cache miss: Fall-through and let caller handle the miss by
  // entering the runtime system.
  __ bind(&miss);
}


#undef __


} }  // namespace v8::internal