// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
#if defined(TARGET_ARCH_X64)

#include "vm/intrinsifier.h"

#include "vm/assembler.h"
#include "vm/dart_entry.h"
#include "vm/flow_graph_compiler.h"
#include "vm/instructions.h"
#include "vm/object_store.h"
#include "vm/regexp_assembler.h"
#include "vm/symbols.h"

namespace dart {

DECLARE_FLAG(bool, interpret_irregexp);

// When entering intrinsics code:
// R10: Arguments descriptor
// TOS: Return address
// The R10 registers can be destroyed only if there is no slow-path, i.e.
// if the intrinsified method always executes a return.
// The RBP register should not be modified, because it is used by the profiler.
// The PP and THR registers (see constants_x64.h) must be preserved.

#define __ assembler->


intptr_t Intrinsifier::ParameterSlotFromSp() { return 0; }


void Intrinsifier::ObjectArraySetIndexed(Assembler* assembler) {
  if (Isolate::Current()->flags().type_checks()) {
    return;
  }

  Label fall_through;
  __ movq(RDX, Address(RSP, + 1 * kWordSize));  // Value.
  __ movq(RCX, Address(RSP, + 2 * kWordSize));  // Index.
  __ movq(RAX, Address(RSP, + 3 * kWordSize));  // Array.
  __ testq(RCX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);
  // Range check.
  __ cmpq(RCX, FieldAddress(RAX, Array::length_offset()));
  // Runtime throws exception.
  __ j(ABOVE_EQUAL, &fall_through);
  // Note that RBX is Smi, i.e, times 2.
  ASSERT(kSmiTagShift == 1);
  // Destroy RCX (ic data) as we will not continue in the function.
  __ StoreIntoObject(RAX,
                     FieldAddress(RAX, RCX, TIMES_4, Array::data_offset()),
                     RDX);
  // Caller is responsible of preserving the value if necessary.
  __ ret();
  __ Bind(&fall_through);
}


// Allocate a GrowableObjectArray using the backing array specified.
// On stack: type argument (+2), data (+1), return-address (+0).
void Intrinsifier::GrowableArray_Allocate(Assembler* assembler) {
  // This snippet of inlined code uses the following registers:
  // RAX, RCX, R13
  // and the newly allocated object is returned in RAX.
  const intptr_t kTypeArgumentsOffset = 2 * kWordSize;
  const intptr_t kArrayOffset = 1 * kWordSize;
  Label fall_through;

  // Try allocating in new space.
  const Class& cls = Class::Handle(
      Isolate::Current()->object_store()->growable_object_array_class());
  __ TryAllocate(cls, &fall_through, Assembler::kFarJump, RAX, R13);

  // Store backing array object in growable array object.
  __ movq(RCX, Address(RSP, kArrayOffset));  // data argument.
  // RAX is new, no barrier needed.
  __ InitializeFieldNoBarrier(
      RAX,
      FieldAddress(RAX, GrowableObjectArray::data_offset()),
      RCX);

  // RAX: new growable array object start as a tagged pointer.
  // Store the type argument field in the growable array object.
  __ movq(RCX, Address(RSP, kTypeArgumentsOffset));  // type argument.
  __ InitializeFieldNoBarrier(
      RAX,
      FieldAddress(RAX, GrowableObjectArray::type_arguments_offset()),
      RCX);

  // Set the length field in the growable array object to 0.
  __ ZeroInitSmiField(FieldAddress(RAX, GrowableObjectArray::length_offset()));
  __ ret();  // returns the newly allocated object in RAX.

  __ Bind(&fall_through);
}


// Add an element to growable array if it doesn't need to grow, otherwise
// call into regular code.
// On stack: growable array (+2), value (+1), return-address (+0).
void Intrinsifier::GrowableArray_add(Assembler* assembler) {
  // In checked mode we need to check the incoming argument.
  if (Isolate::Current()->flags().type_checks()) return;
  Label fall_through;
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // Array.
  __ movq(RCX, FieldAddress(RAX, GrowableObjectArray::length_offset()));
  // RCX: length.
  __ movq(RDX, FieldAddress(RAX, GrowableObjectArray::data_offset()));
  // RDX: data.
  // Compare length with capacity.
  __ cmpq(RCX, FieldAddress(RDX, Array::length_offset()));
  __ j(EQUAL, &fall_through);  // Must grow data.
  // len = len + 1;
  __ IncrementSmiField(FieldAddress(RAX, GrowableObjectArray::length_offset()),
                       1);
  __ movq(RAX, Address(RSP, + 1 * kWordSize));  // Value
  ASSERT(kSmiTagShift == 1);
  __ StoreIntoObject(RDX,
                     FieldAddress(RDX, RCX, TIMES_4, Array::data_offset()),
                     RAX);
  __ LoadObject(RAX, Object::null_object());
  __ ret();
  __ Bind(&fall_through);
}


#define TYPED_ARRAY_ALLOCATION(type_name, cid, max_len, scale_factor)          \
  Label fall_through;                                                          \
  const intptr_t kArrayLengthStackOffset = 1 * kWordSize;                      \
  __ MaybeTraceAllocation(cid, &fall_through, false,                           \
                          /* inline_isolate = */ false);                       \
  __ movq(RDI, Address(RSP, kArrayLengthStackOffset));  /* Array length. */    \
  /* Check that length is a positive Smi. */                                   \
  /* RDI: requested array length argument. */                                  \
  __ testq(RDI, Immediate(kSmiTagMask));                                       \
  __ j(NOT_ZERO, &fall_through);                                               \
  __ cmpq(RDI, Immediate(0));                                                  \
  __ j(LESS, &fall_through);                                                   \
  __ SmiUntag(RDI);                                                            \
  /* Check for maximum allowed length. */                                      \
  /* RDI: untagged array length. */                                            \
  __ cmpq(RDI, Immediate(max_len));                                            \
  __ j(GREATER, &fall_through);                                                \
  /* Special case for scaling by 16. */                                        \
  if (scale_factor == TIMES_16) {                                              \
    /* double length of array. */                                              \
    __ addq(RDI, RDI);                                                         \
    /* only scale by 8. */                                                     \
    scale_factor = TIMES_8;                                                    \
  }                                                                            \
  const intptr_t fixed_size = sizeof(Raw##type_name) + kObjectAlignment - 1;   \
  __ leaq(RDI, Address(RDI, scale_factor, fixed_size));                        \
  __ andq(RDI, Immediate(-kObjectAlignment));                                  \
  Heap::Space space = Heap::SpaceForAllocation(cid);                           \
  __ movq(R13, Address(THR, Thread::heap_offset()));                           \
  __ movq(RAX, Address(R13, Heap::TopOffset(space)));                          \
  __ movq(RCX, RAX);                                                           \
                                                                               \
  /* RDI: allocation size. */                                                  \
  __ addq(RCX, RDI);                                                           \
  __ j(CARRY, &fall_through);                                                  \
                                                                               \
  /* Check if the allocation fits into the remaining space. */                 \
  /* RAX: potential new object start. */                                       \
  /* RCX: potential next object start. */                                      \
  /* RDI: allocation size. */                                                  \
  /* R13: heap. */                                                             \
  __ cmpq(RCX, Address(R13, Heap::EndOffset(space)));                          \
  __ j(ABOVE_EQUAL, &fall_through);                                            \
                                                                               \
  /* Successfully allocated the object(s), now update top to point to */       \
  /* next object start and initialize the object. */                           \
  __ movq(Address(R13, Heap::TopOffset(space)), RCX);                          \
  __ addq(RAX, Immediate(kHeapObjectTag));                                     \
  __ UpdateAllocationStatsWithSize(cid, RDI, space,                            \
                                   /* inline_isolate = */ false);              \
  /* Initialize the tags. */                                                   \
  /* RAX: new object start as a tagged pointer. */                             \
  /* RCX: new object end address. */                                           \
  /* RDI: allocation size. */                                                  \
  /* R13: scratch register. */                                                 \
  {                                                                            \
    Label size_tag_overflow, done;                                             \
    __ cmpq(RDI, Immediate(RawObject::SizeTag::kMaxSizeTag));                  \
    __ j(ABOVE, &size_tag_overflow, Assembler::kNearJump);                     \
    __ shlq(RDI, Immediate(RawObject::kSizeTagPos - kObjectAlignmentLog2));    \
    __ jmp(&done, Assembler::kNearJump);                                       \
                                                                               \
    __ Bind(&size_tag_overflow);                                               \
    __ movq(RDI, Immediate(0));                                                \
    __ Bind(&done);                                                            \
                                                                               \
    /* Get the class index and insert it into the tags. */                     \
    __ orq(RDI, Immediate(RawObject::ClassIdTag::encode(cid)));                \
    __ movq(FieldAddress(RAX, type_name::tags_offset()), RDI);  /* Tags. */    \
  }                                                                            \
  /* Set the length field. */                                                  \
  /* RAX: new object start as a tagged pointer. */                             \
  /* RCX: new object end address. */                                           \
  __ movq(RDI, Address(RSP, kArrayLengthStackOffset));  /* Array length. */    \
  __ InitializeFieldNoBarrier(RAX,                                             \
                              FieldAddress(RAX, type_name::length_offset()),   \
                              RDI);                                            \
  /* Initialize all array elements to 0. */                                    \
  /* RAX: new object start as a tagged pointer. */                             \
  /* RCX: new object end address. */                                           \
  /* RDI: iterator which initially points to the start of the variable */      \
  /* RBX: scratch register. */                                                 \
  /* data area to be initialized. */                                           \
  __ xorq(RBX, RBX);  /* Zero. */                                              \
  __ leaq(RDI, FieldAddress(RAX, sizeof(Raw##type_name)));                     \
  Label done, init_loop;                                                       \
  __ Bind(&init_loop);                                                         \
  __ cmpq(RDI, RCX);                                                           \
  __ j(ABOVE_EQUAL, &done, Assembler::kNearJump);                              \
  __ movq(Address(RDI, 0), RBX);                                               \
  __ addq(RDI, Immediate(kWordSize));                                          \
  __ jmp(&init_loop, Assembler::kNearJump);                                    \
  __ Bind(&done);                                                              \
                                                                               \
  __ ret();                                                                    \
  __ Bind(&fall_through);                                                      \


static ScaleFactor GetScaleFactor(intptr_t size) {
  switch (size) {
    case 1: return TIMES_1;
    case 2: return TIMES_2;
    case 4: return TIMES_4;
    case 8: return TIMES_8;
    case 16: return TIMES_16;
  }
  UNREACHABLE();
  return static_cast<ScaleFactor>(0);
}


#define TYPED_DATA_ALLOCATOR(clazz)                                            \
void Intrinsifier::TypedData_##clazz##_new(Assembler* assembler) {             \
  intptr_t size = TypedData::ElementSizeInBytes(kTypedData##clazz##Cid);       \
  intptr_t max_len = TypedData::MaxElements(kTypedData##clazz##Cid);           \
  ScaleFactor scale = GetScaleFactor(size);                                    \
  TYPED_ARRAY_ALLOCATION(TypedData, kTypedData##clazz##Cid, max_len, scale);   \
}                                                                              \
void Intrinsifier::TypedData_##clazz##_factory(Assembler* assembler) {         \
  intptr_t size = TypedData::ElementSizeInBytes(kTypedData##clazz##Cid);       \
  intptr_t max_len = TypedData::MaxElements(kTypedData##clazz##Cid);           \
  ScaleFactor scale = GetScaleFactor(size);                                    \
  TYPED_ARRAY_ALLOCATION(TypedData, kTypedData##clazz##Cid, max_len, scale);   \
}
CLASS_LIST_TYPED_DATA(TYPED_DATA_ALLOCATOR)
#undef TYPED_DATA_ALLOCATOR


// Tests if two top most arguments are smis, jumps to label not_smi if not.
// Topmost argument is in RAX.
static void TestBothArgumentsSmis(Assembler* assembler, Label* not_smi) {
  __ movq(RAX, Address(RSP, + 1 * kWordSize));
  __ movq(RCX, Address(RSP, + 2 * kWordSize));
  __ orq(RCX, RAX);
  __ testq(RCX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, not_smi);
}


void Intrinsifier::Integer_addFromInteger(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX contains right argument.
  __ addq(RAX, Address(RSP, + 2 * kWordSize));
  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_add(Assembler* assembler) {
  Integer_addFromInteger(assembler);
}


void Intrinsifier::Integer_subFromInteger(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX contains right argument, which is the actual minuend of subtraction.
  __ subq(RAX, Address(RSP, + 2 * kWordSize));
  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_sub(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX contains right argument, which is the actual subtrahend of subtraction.
  __ movq(RCX, RAX);
  __ movq(RAX, Address(RSP, + 2 * kWordSize));
  __ subq(RAX, RCX);
  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_mulFromInteger(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX is the right argument.
  ASSERT(kSmiTag == 0);  // Adjust code below if not the case.
  __ SmiUntag(RAX);
  __ imulq(RAX, Address(RSP, + 2 * kWordSize));
  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_mul(Assembler* assembler) {
  Integer_mulFromInteger(assembler);
}


// Optimizations:
// - result is 0 if:
//   - left is 0
//   - left equals right
// - result is left if
//   - left > 0 && left < right
// RAX: Tagged left (dividend).
// RCX: Tagged right (divisor).
// Returns:
//   RAX: Untagged fallthrough result (remainder to be adjusted), or
//   RAX: Tagged return result (remainder).
static void EmitRemainderOperation(Assembler* assembler) {
  Label return_zero, try_modulo, not_32bit, done;
  // Check for quick zero results.
  __ cmpq(RAX, Immediate(0));
  __ j(EQUAL, &return_zero, Assembler::kNearJump);
  __ cmpq(RAX, RCX);
  __ j(EQUAL, &return_zero, Assembler::kNearJump);

  // Check if result equals left.
  __ cmpq(RAX, Immediate(0));
  __ j(LESS, &try_modulo, Assembler::kNearJump);
  // left is positive.
  __ cmpq(RAX, RCX);
  __ j(GREATER, &try_modulo,  Assembler::kNearJump);
  // left is less than right, result is left (RAX).
  __ ret();

  __ Bind(&return_zero);
  __ xorq(RAX, RAX);
  __ ret();

  __ Bind(&try_modulo);

  // Check if both operands fit into 32bits as idiv with 64bit operands
  // requires twice as many cycles and has much higher latency. We are checking
  // this before untagging them to avoid corner case dividing INT_MAX by -1 that
  // raises exception because quotient is too large for 32bit register.
  __ movsxd(RBX, RAX);
  __ cmpq(RBX, RAX);
  __ j(NOT_EQUAL, &not_32bit, Assembler::kNearJump);
  __ movsxd(RBX, RCX);
  __ cmpq(RBX, RCX);
  __ j(NOT_EQUAL, &not_32bit, Assembler::kNearJump);

  // Both operands are 31bit smis. Divide using 32bit idiv.
  __ SmiUntag(RAX);
  __ SmiUntag(RCX);
  __ cdq();
  __ idivl(RCX);
  __ movsxd(RAX, RDX);
  __ jmp(&done, Assembler::kNearJump);

  // Divide using 64bit idiv.
  __ Bind(&not_32bit);
  __ SmiUntag(RAX);
  __ SmiUntag(RCX);
  __ cqo();
  __ idivq(RCX);
  __ movq(RAX, RDX);
  __ Bind(&done);
}


// Implementation:
//  res = left % right;
//  if (res < 0) {
//    if (right < 0) {
//      res = res - right;
//    } else {
//      res = res + right;
//    }
//  }
void Intrinsifier::Integer_moduloFromInteger(Assembler* assembler) {
  Label fall_through, negative_result;
  TestBothArgumentsSmis(assembler, &fall_through);
  __ movq(RCX, Address(RSP, + 2 * kWordSize));
  // RAX: Tagged left (dividend).
  // RCX: Tagged right (divisor).
  __ cmpq(RCX, Immediate(0));
  __ j(EQUAL, &fall_through);
  EmitRemainderOperation(assembler);
  // Untagged remainder result in RAX.
  __ cmpq(RAX, Immediate(0));
  __ j(LESS, &negative_result, Assembler::kNearJump);
  __ SmiTag(RAX);
  __ ret();

  __ Bind(&negative_result);
  Label subtract;
  // RAX: Untagged result.
  // RCX: Untagged right.
  __ cmpq(RCX, Immediate(0));
  __ j(LESS, &subtract, Assembler::kNearJump);
  __ addq(RAX, RCX);
  __ SmiTag(RAX);
  __ ret();

  __ Bind(&subtract);
  __ subq(RAX, RCX);
  __ SmiTag(RAX);
  __ ret();

  __ Bind(&fall_through);
}


void Intrinsifier::Integer_truncDivide(Assembler* assembler) {
  Label fall_through, not_32bit;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX: right argument (divisor)
  __ cmpq(RAX, Immediate(0));
  __ j(EQUAL, &fall_through, Assembler::kNearJump);
  __ movq(RCX, RAX);
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // Left argument (dividend).

  // Check if both operands fit into 32bits as idiv with 64bit operands
  // requires twice as many cycles and has much higher latency. We are checking
  // this before untagging them to avoid corner case dividing INT_MAX by -1 that
  // raises exception because quotient is too large for 32bit register.
  __ movsxd(RBX, RAX);
  __ cmpq(RBX, RAX);
  __ j(NOT_EQUAL, &not_32bit);
  __ movsxd(RBX, RCX);
  __ cmpq(RBX, RCX);
  __ j(NOT_EQUAL, &not_32bit);

  // Both operands are 31bit smis. Divide using 32bit idiv.
  __ SmiUntag(RAX);
  __ SmiUntag(RCX);
  __ cdq();
  __ idivl(RCX);
  __ movsxd(RAX, RAX);
  __ SmiTag(RAX);  // Result is guaranteed to fit into a smi.
  __ ret();

  // Divide using 64bit idiv.
  __ Bind(&not_32bit);
  __ SmiUntag(RAX);
  __ SmiUntag(RCX);
  __ pushq(RDX);  // Preserve RDX in case of 'fall_through'.
  __ cqo();
  __ idivq(RCX);
  __ popq(RDX);
  // Check the corner case of dividing the 'MIN_SMI' with -1, in which case we
  // cannot tag the result.
  __ cmpq(RAX, Immediate(0x4000000000000000));
  __ j(EQUAL, &fall_through);
  __ SmiTag(RAX);
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_negate(Assembler* assembler) {
  Label fall_through;
  __ movq(RAX, Address(RSP, + 1 * kWordSize));
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through, Assembler::kNearJump);  // Non-smi value.
  __ negq(RAX);
  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_bitAndFromInteger(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX is the right argument.
  __ andq(RAX, Address(RSP, + 2 * kWordSize));
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_bitAnd(Assembler* assembler) {
  Integer_bitAndFromInteger(assembler);
}


void Intrinsifier::Integer_bitOrFromInteger(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX is the right argument.
  __ orq(RAX, Address(RSP, + 2 * kWordSize));
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_bitOr(Assembler* assembler) {
  Integer_bitOrFromInteger(assembler);
}


void Intrinsifier::Integer_bitXorFromInteger(Assembler* assembler) {
  Label fall_through;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX is the right argument.
  __ xorq(RAX, Address(RSP, + 2 * kWordSize));
  // Result is in RAX.
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_bitXor(Assembler* assembler) {
  Integer_bitXorFromInteger(assembler);
}


void Intrinsifier::Integer_shl(Assembler* assembler) {
  ASSERT(kSmiTagShift == 1);
  ASSERT(kSmiTag == 0);
  Label fall_through, overflow;
  TestBothArgumentsSmis(assembler, &fall_through);
  // Shift value is in RAX. Compare with tagged Smi.
  __ cmpq(RAX, Immediate(Smi::RawValue(Smi::kBits)));
  __ j(ABOVE_EQUAL, &fall_through, Assembler::kNearJump);

  __ SmiUntag(RAX);
  __ movq(RCX, RAX);  // Shift amount must be in RCX.
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // Value.

  // Overflow test - all the shifted-out bits must be same as the sign bit.
  __ movq(RDI, RAX);
  __ shlq(RAX, RCX);
  __ sarq(RAX, RCX);
  __ cmpq(RAX, RDI);
  __ j(NOT_EQUAL, &overflow, Assembler::kNearJump);

  __ shlq(RAX, RCX);  // Shift for result now we know there is no overflow.

  // RAX is a correctly tagged Smi.
  __ ret();

  __ Bind(&overflow);
  // Mint is rarely used on x64 (only for integers requiring 64 bit instead of
  // 63 bits as represented by Smi).
  __ Bind(&fall_through);
}


static void CompareIntegers(Assembler* assembler, Condition true_condition) {
  Label fall_through, true_label;
  TestBothArgumentsSmis(assembler, &fall_through);
  // RAX contains the right argument.
  __ cmpq(Address(RSP, + 2 * kWordSize), RAX);
  __ j(true_condition, &true_label, Assembler::kNearJump);
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&true_label);
  __ LoadObject(RAX, Bool::True());
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Integer_lessThan(Assembler* assembler) {
  CompareIntegers(assembler, LESS);
}


void Intrinsifier::Integer_greaterThanFromInt(Assembler* assembler) {
  CompareIntegers(assembler, LESS);
}


void Intrinsifier::Integer_greaterThan(Assembler* assembler) {
  CompareIntegers(assembler, GREATER);
}


void Intrinsifier::Integer_lessEqualThan(Assembler* assembler) {
  CompareIntegers(assembler, LESS_EQUAL);
}


void Intrinsifier::Integer_greaterEqualThan(Assembler* assembler) {
  CompareIntegers(assembler, GREATER_EQUAL);
}


// This is called for Smi, Mint and Bigint receivers. The right argument
// can be Smi, Mint, Bigint or double.
void Intrinsifier::Integer_equalToInteger(Assembler* assembler) {
  Label fall_through, true_label, check_for_mint;
  const intptr_t kReceiverOffset = 2;
  const intptr_t kArgumentOffset = 1;

  // For integer receiver '===' check first.
  __ movq(RAX, Address(RSP, + kArgumentOffset * kWordSize));
  __ movq(RCX, Address(RSP, + kReceiverOffset * kWordSize));
  __ cmpq(RAX, RCX);
  __ j(EQUAL, &true_label, Assembler::kNearJump);
  __ orq(RAX, RCX);
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &check_for_mint, Assembler::kNearJump);
  // Both arguments are smi, '===' is good enough.
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&true_label);
  __ LoadObject(RAX, Bool::True());
  __ ret();

  // At least one of the arguments was not Smi.
  Label receiver_not_smi;
  __ Bind(&check_for_mint);
  __ movq(RAX, Address(RSP, + kReceiverOffset * kWordSize));
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &receiver_not_smi);

  // Left (receiver) is Smi, return false if right is not Double.
  // Note that an instance of Mint or Bigint never contains a value that can be
  // represented by Smi.
  __ movq(RAX, Address(RSP, + kArgumentOffset * kWordSize));
  __ CompareClassId(RAX, kDoubleCid);
  __ j(EQUAL, &fall_through);
  __ LoadObject(RAX, Bool::False());
  __ ret();

  __ Bind(&receiver_not_smi);
  // RAX:: receiver.
  __ CompareClassId(RAX, kMintCid);
  __ j(NOT_EQUAL, &fall_through);
  // Receiver is Mint, return false if right is Smi.
  __ movq(RAX, Address(RSP, + kArgumentOffset * kWordSize));
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);
  // Smi == Mint -> false.
  __ LoadObject(RAX, Bool::False());
  __ ret();
  // TODO(srdjan): Implement Mint == Mint comparison.

  __ Bind(&fall_through);
}


void Intrinsifier::Integer_equal(Assembler* assembler) {
  Integer_equalToInteger(assembler);
}


void Intrinsifier::Integer_sar(Assembler* assembler) {
  Label fall_through, shift_count_ok;
  TestBothArgumentsSmis(assembler, &fall_through);
  const Immediate& count_limit = Immediate(0x3F);
  // Check that the count is not larger than what the hardware can handle.
  // For shifting right a Smi the result is the same for all numbers
  // >= count_limit.
  __ SmiUntag(RAX);
  // Negative counts throw exception.
  __ cmpq(RAX, Immediate(0));
  __ j(LESS, &fall_through, Assembler::kNearJump);
  __ cmpq(RAX, count_limit);
  __ j(LESS_EQUAL, &shift_count_ok, Assembler::kNearJump);
  __ movq(RAX, count_limit);
  __ Bind(&shift_count_ok);
  __ movq(RCX, RAX);  // Shift amount must be in RCX.
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // Value.
  __ SmiUntag(RAX);  // Value.
  __ sarq(RAX, RCX);
  __ SmiTag(RAX);
  __ ret();
  __ Bind(&fall_through);
}


// Argument is Smi (receiver).
void Intrinsifier::Smi_bitNegate(Assembler* assembler) {
  __ movq(RAX, Address(RSP, + 1 * kWordSize));  // Index.
  __ notq(RAX);
  __ andq(RAX, Immediate(~kSmiTagMask));  // Remove inverted smi-tag.
  __ ret();
}


void Intrinsifier::Smi_bitLength(Assembler* assembler) {
  ASSERT(kSmiTagShift == 1);
  __ movq(RAX, Address(RSP, + 1 * kWordSize));  // Index.
  // XOR with sign bit to complement bits if value is negative.
  __ movq(RCX, RAX);
  __ sarq(RCX, Immediate(63));  // All 0 or all 1.
  __ xorq(RAX, RCX);
  // BSR does not write the destination register if source is zero.  Put a 1 in
  // the Smi tag bit to ensure BSR writes to destination register.
  __ orq(RAX, Immediate(kSmiTagMask));
  __ bsrq(RAX, RAX);
  __ SmiTag(RAX);
  __ ret();
}


void Intrinsifier::Bigint_lsh(Assembler* assembler) {
  // static void _lsh(Uint32List x_digits, int x_used, int n,
  //                  Uint32List r_digits)

  __ movq(RDI, Address(RSP, 4 * kWordSize));  // x_digits
  __ movq(R8, Address(RSP, 3 * kWordSize));  // x_used is Smi
  __ subq(R8, Immediate(2));  // x_used > 0, Smi. R8 = x_used - 1, round up.
  __ sarq(R8, Immediate(2));  // R8 + 1 = number of digit pairs to read.
  __ movq(RCX, Address(RSP, 2 * kWordSize));  // n is Smi
  __ SmiUntag(RCX);
  __ movq(RBX, Address(RSP, 1 * kWordSize));  // r_digits
  __ movq(RSI, RCX);
  __ sarq(RSI, Immediate(6));  // RSI = n ~/ (2*_DIGIT_BITS).
  __ leaq(RBX, FieldAddress(RBX, RSI, TIMES_8, TypedData::data_offset()));
  __ xorq(RAX, RAX);  // RAX = 0.
  __ movq(RDX, FieldAddress(RDI, R8, TIMES_8, TypedData::data_offset()));
  __ shldq(RAX, RDX, RCX);
  __ movq(Address(RBX, R8, TIMES_8, 2 * Bigint::kBytesPerDigit), RAX);
  Label last;
  __ cmpq(R8, Immediate(0));
  __ j(EQUAL, &last, Assembler::kNearJump);
  Label loop;
  __ Bind(&loop);
  __ movq(RAX, RDX);
  __ movq(RDX,
          FieldAddress(RDI, R8, TIMES_8,
                       TypedData::data_offset() - 2 * Bigint::kBytesPerDigit));
  __ shldq(RAX, RDX, RCX);
  __ movq(Address(RBX, R8, TIMES_8, 0), RAX);
  __ decq(R8);
  __ j(NOT_ZERO, &loop, Assembler::kNearJump);
  __ Bind(&last);
  __ shldq(RDX, R8, RCX);  // R8 == 0.
  __ movq(Address(RBX, 0), RDX);
  // Returning Object::null() is not required, since this method is private.
  __ ret();
}


void Intrinsifier::Bigint_rsh(Assembler* assembler) {
  // static void _rsh(Uint32List x_digits, int x_used, int n,
  //                  Uint32List r_digits)

  __ movq(RDI, Address(RSP, 4 * kWordSize));  // x_digits
  __ movq(RCX, Address(RSP, 2 * kWordSize));  // n is Smi
  __ SmiUntag(RCX);
  __ movq(RBX, Address(RSP, 1 * kWordSize));  // r_digits
  __ movq(RDX, RCX);
  __ sarq(RDX, Immediate(6));  // RDX = n ~/ (2*_DIGIT_BITS).
  __ movq(RSI, Address(RSP, 3 * kWordSize));  // x_used is Smi
  __ subq(RSI, Immediate(2));  // x_used > 0, Smi. RSI = x_used - 1, round up.
  __ sarq(RSI, Immediate(2));
  __ leaq(RDI, FieldAddress(RDI, RSI, TIMES_8, TypedData::data_offset()));
  __ subq(RSI, RDX);  // RSI + 1 = number of digit pairs to read.
  __ leaq(RBX, FieldAddress(RBX, RSI, TIMES_8, TypedData::data_offset()));
  __ negq(RSI);
  __ movq(RDX, Address(RDI, RSI, TIMES_8, 0));
  Label last;
  __ cmpq(RSI, Immediate(0));
  __ j(EQUAL, &last, Assembler::kNearJump);
  Label loop;
  __ Bind(&loop);
  __ movq(RAX, RDX);
  __ movq(RDX, Address(RDI, RSI, TIMES_8, 2 * Bigint::kBytesPerDigit));
  __ shrdq(RAX, RDX, RCX);
  __ movq(Address(RBX, RSI, TIMES_8, 0), RAX);
  __ incq(RSI);
  __ j(NOT_ZERO, &loop, Assembler::kNearJump);
  __ Bind(&last);
  __ shrdq(RDX, RSI, RCX);  // RSI == 0.
  __ movq(Address(RBX, 0), RDX);
  // Returning Object::null() is not required, since this method is private.
  __ ret();
}


void Intrinsifier::Bigint_absAdd(Assembler* assembler) {
  // static void _absAdd(Uint32List digits, int used,
  //                     Uint32List a_digits, int a_used,
  //                     Uint32List r_digits)

  __ movq(RDI, Address(RSP, 5 * kWordSize));  // digits
  __ movq(R8, Address(RSP, 4 * kWordSize));  // used is Smi
  __ addq(R8, Immediate(2));  // used > 0, Smi. R8 = used + 1, round up.
  __ sarq(R8, Immediate(2));  // R8 = number of digit pairs to process.
  __ movq(RSI, Address(RSP, 3 * kWordSize));  // a_digits
  __ movq(RCX, Address(RSP, 2 * kWordSize));  // a_used is Smi
  __ addq(RCX, Immediate(2));  // a_used > 0, Smi. R8 = a_used + 1, round up.
  __ sarq(RCX, Immediate(2));  // R8 = number of digit pairs to process.
  __ movq(RBX, Address(RSP, 1 * kWordSize));  // r_digits

  // Precompute 'used - a_used' now so that carry flag is not lost later.
  __ subq(R8, RCX);
  __ incq(R8);  // To account for the extra test between loops.

  __ xorq(RDX, RDX);  // RDX = 0, carry flag = 0.
  Label add_loop;
  __ Bind(&add_loop);
  // Loop (a_used+1)/2 times, RCX > 0.
  __ movq(RAX, FieldAddress(RDI, RDX, TIMES_8, TypedData::data_offset()));
  __ adcq(RAX, FieldAddress(RSI, RDX, TIMES_8, TypedData::data_offset()));
  __ movq(FieldAddress(RBX, RDX, TIMES_8, TypedData::data_offset()), RAX);
  __ incq(RDX);  // Does not affect carry flag.
  __ decq(RCX);  // Does not affect carry flag.
  __ j(NOT_ZERO, &add_loop, Assembler::kNearJump);

  Label last_carry;
  __ decq(R8);  // Does not affect carry flag.
  __ j(ZERO, &last_carry, Assembler::kNearJump);  // If used - a_used == 0.

  Label carry_loop;
  __ Bind(&carry_loop);
  // Loop (used+1)/2 - (a_used+1)/2 times, R8 > 0.
  __ movq(RAX, FieldAddress(RDI, RDX, TIMES_8, TypedData::data_offset()));
  __ adcq(RAX, Immediate(0));
  __ movq(FieldAddress(RBX, RDX, TIMES_8, TypedData::data_offset()), RAX);
  __ incq(RDX);  // Does not affect carry flag.
  __ decq(R8);  // Does not affect carry flag.
  __ j(NOT_ZERO, &carry_loop, Assembler::kNearJump);

  __ Bind(&last_carry);
  Label done;
  __ j(NOT_CARRY, &done);
  __ movq(FieldAddress(RBX, RDX, TIMES_8, TypedData::data_offset()),
          Immediate(1));

  __ Bind(&done);
  // Returning Object::null() is not required, since this method is private.
  __ ret();
}


void Intrinsifier::Bigint_absSub(Assembler* assembler) {
  // static void _absSub(Uint32List digits, int used,
  //                     Uint32List a_digits, int a_used,
  //                     Uint32List r_digits)

  __ movq(RDI, Address(RSP, 5 * kWordSize));  // digits
  __ movq(R8, Address(RSP, 4 * kWordSize));  // used is Smi
  __ addq(R8, Immediate(2));  // used > 0, Smi. R8 = used + 1, round up.
  __ sarq(R8, Immediate(2));  // R8 = number of digit pairs to process.
  __ movq(RSI, Address(RSP, 3 * kWordSize));  // a_digits
  __ movq(RCX, Address(RSP, 2 * kWordSize));  // a_used is Smi
  __ addq(RCX, Immediate(2));  // a_used > 0, Smi. R8 = a_used + 1, round up.
  __ sarq(RCX, Immediate(2));  // R8 = number of digit pairs to process.
  __ movq(RBX, Address(RSP, 1 * kWordSize));  // r_digits

  // Precompute 'used - a_used' now so that carry flag is not lost later.
  __ subq(R8, RCX);
  __ incq(R8);  // To account for the extra test between loops.

  __ xorq(RDX, RDX);  // RDX = 0, carry flag = 0.
  Label sub_loop;
  __ Bind(&sub_loop);
  // Loop (a_used+1)/2 times, RCX > 0.
  __ movq(RAX, FieldAddress(RDI, RDX, TIMES_8, TypedData::data_offset()));
  __ sbbq(RAX, FieldAddress(RSI, RDX, TIMES_8, TypedData::data_offset()));
  __ movq(FieldAddress(RBX, RDX, TIMES_8, TypedData::data_offset()), RAX);
  __ incq(RDX);  // Does not affect carry flag.
  __ decq(RCX);  // Does not affect carry flag.
  __ j(NOT_ZERO, &sub_loop, Assembler::kNearJump);

  Label done;
  __ decq(R8);  // Does not affect carry flag.
  __ j(ZERO, &done, Assembler::kNearJump);  // If used - a_used == 0.

  Label carry_loop;
  __ Bind(&carry_loop);
  // Loop (used+1)/2 - (a_used+1)/2 times, R8 > 0.
  __ movq(RAX, FieldAddress(RDI, RDX, TIMES_8, TypedData::data_offset()));
  __ sbbq(RAX, Immediate(0));
  __ movq(FieldAddress(RBX, RDX, TIMES_8, TypedData::data_offset()), RAX);
  __ incq(RDX);  // Does not affect carry flag.
  __ decq(R8);  // Does not affect carry flag.
  __ j(NOT_ZERO, &carry_loop, Assembler::kNearJump);

  __ Bind(&done);
  // Returning Object::null() is not required, since this method is private.
  __ ret();
}


void Intrinsifier::Bigint_mulAdd(Assembler* assembler) {
  // Pseudo code:
  // static int _mulAdd(Uint32List x_digits, int xi,
  //                    Uint32List m_digits, int i,
  //                    Uint32List a_digits, int j, int n) {
  //   uint64_t x = x_digits[xi >> 1 .. (xi >> 1) + 1];  // xi is Smi and even.
  //   if (x == 0 || n == 0) {
  //     return 2;
  //   }
  //   uint64_t* mip = &m_digits[i >> 1];  // i is Smi and even.
  //   uint64_t* ajp = &a_digits[j >> 1];  // j is Smi and even.
  //   uint64_t c = 0;
  //   SmiUntag(n);  // n is Smi and even.
  //   n = (n + 1)/2;  // Number of pairs to process.
  //   do {
  //     uint64_t mi = *mip++;
  //     uint64_t aj = *ajp;
  //     uint128_t t = x*mi + aj + c;  // 64-bit * 64-bit -> 128-bit.
  //     *ajp++ = low64(t);
  //     c = high64(t);
  //   } while (--n > 0);
  //   while (c != 0) {
  //     uint128_t t = *ajp + c;
  //     *ajp++ = low64(t);
  //     c = high64(t);  // c == 0 or 1.
  //   }
  //   return 2;
  // }

  Label done;
  // RBX = x, done if x == 0
  __ movq(RCX, Address(RSP, 7 * kWordSize));  // x_digits
  __ movq(RAX, Address(RSP, 6 * kWordSize));  // xi is Smi
  __ movq(RBX, FieldAddress(RCX, RAX, TIMES_2, TypedData::data_offset()));
  __ testq(RBX, RBX);
  __ j(ZERO, &done, Assembler::kNearJump);

  // R8 = (SmiUntag(n) + 1)/2, no_op if n == 0
  __ movq(R8, Address(RSP, 1 * kWordSize));
  __ addq(R8, Immediate(2));
  __ sarq(R8, Immediate(2));  // R8 = number of digit pairs to process.
  __ j(ZERO, &done, Assembler::kNearJump);

  // RDI = mip = &m_digits[i >> 1]
  __ movq(RDI, Address(RSP, 5 * kWordSize));  // m_digits
  __ movq(RAX, Address(RSP, 4 * kWordSize));  // i is Smi
  __ leaq(RDI, FieldAddress(RDI, RAX, TIMES_2, TypedData::data_offset()));

  // RSI = ajp = &a_digits[j >> 1]
  __ movq(RSI, Address(RSP, 3 * kWordSize));  // a_digits
  __ movq(RAX, Address(RSP, 2 * kWordSize));  // j is Smi
  __ leaq(RSI, FieldAddress(RSI, RAX, TIMES_2, TypedData::data_offset()));

  // RCX = c = 0
  __ xorq(RCX, RCX);

  Label muladd_loop;
  __ Bind(&muladd_loop);
  // x:   RBX
  // mip: RDI
  // ajp: RSI
  // c:   RCX
  // t:   RDX:RAX (not live at loop entry)
  // n:   R8

  // uint64_t mi = *mip++
  __ movq(RAX, Address(RDI, 0));
  __ addq(RDI, Immediate(2*Bigint::kBytesPerDigit));

  // uint128_t t = x*mi
  __ mulq(RBX);  // t = RDX:RAX = RAX * RBX, 64-bit * 64-bit -> 64-bit
  __ addq(RAX, RCX);  // t += c
  __ adcq(RDX, Immediate(0));

  // uint64_t aj = *ajp; t += aj
  __ addq(RAX, Address(RSI, 0));
  __ adcq(RDX, Immediate(0));

  // *ajp++ = low64(t)
  __ movq(Address(RSI, 0), RAX);
  __ addq(RSI, Immediate(2*Bigint::kBytesPerDigit));

  // c = high64(t)
  __ movq(RCX, RDX);

  // while (--n > 0)
  __ decq(R8);  // --n
  __ j(NOT_ZERO, &muladd_loop, Assembler::kNearJump);

  __ testq(RCX, RCX);
  __ j(ZERO, &done, Assembler::kNearJump);

  // *ajp += c
  __ addq(Address(RSI, 0), RCX);
  __ j(NOT_CARRY, &done, Assembler::kNearJump);

  Label propagate_carry_loop;
  __ Bind(&propagate_carry_loop);
  __ addq(RSI, Immediate(2*Bigint::kBytesPerDigit));
  __ incq(Address(RSI, 0));  // c == 0 or 1
  __ j(CARRY, &propagate_carry_loop, Assembler::kNearJump);

  __ Bind(&done);
  __ movq(RAX, Immediate(Smi::RawValue(2)));  // Two digits processed.
  __ ret();
}


void Intrinsifier::Bigint_sqrAdd(Assembler* assembler) {
  // Pseudo code:
  // static int _sqrAdd(Uint32List x_digits, int i,
  //                    Uint32List a_digits, int used) {
  //   uint64_t* xip = &x_digits[i >> 1];  // i is Smi and even.
  //   uint64_t x = *xip++;
  //   if (x == 0) return 2;
  //   uint64_t* ajp = &a_digits[i];  // j == 2*i, i is Smi.
  //   uint64_t aj = *ajp;
  //   uint128_t t = x*x + aj;
  //   *ajp++ = low64(t);
  //   uint128_t c = high64(t);
  //   int n = ((used - i + 2) >> 2) - 1;  // used and i are Smi. n: num pairs.
  //   while (--n >= 0) {
  //     uint64_t xi = *xip++;
  //     uint64_t aj = *ajp;
  //     uint192_t t = 2*x*xi + aj + c;  // 2-bit * 64-bit * 64-bit -> 129-bit.
  //     *ajp++ = low64(t);
  //     c = high128(t);  // 65-bit.
  //   }
  //   uint64_t aj = *ajp;
  //   uint128_t t = aj + c;  // 64-bit + 65-bit -> 66-bit.
  //   *ajp++ = low64(t);
  //   *ajp = high64(t);
  //   return 2;
  // }

  // RDI = xip = &x_digits[i >> 1]
  __ movq(RDI, Address(RSP, 4 * kWordSize));  // x_digits
  __ movq(RAX, Address(RSP, 3 * kWordSize));  // i is Smi
  __ leaq(RDI, FieldAddress(RDI, RAX, TIMES_2, TypedData::data_offset()));

  // RBX = x = *xip++, return if x == 0
  Label x_zero;
  __ movq(RBX, Address(RDI, 0));
  __ cmpq(RBX, Immediate(0));
  __ j(EQUAL, &x_zero);
  __ addq(RDI, Immediate(2*Bigint::kBytesPerDigit));

  // RSI = ajp = &a_digits[i]
  __ movq(RSI, Address(RSP, 2 * kWordSize));  // a_digits
  __ leaq(RSI, FieldAddress(RSI, RAX, TIMES_4, TypedData::data_offset()));

  // RDX:RAX = t = x*x + *ajp
  __ movq(RAX, RBX);
  __ mulq(RBX);
  __ addq(RAX, Address(RSI, 0));
  __ adcq(RDX, Immediate(0));

  // *ajp++ = low64(t)
  __ movq(Address(RSI, 0), RAX);
  __ addq(RSI, Immediate(2*Bigint::kBytesPerDigit));

  // int n = (used - i + 1)/2 - 1
  __ movq(R8, Address(RSP, 1 * kWordSize));  // used is Smi
  __ subq(R8, Address(RSP, 3 * kWordSize));  // i is Smi
  __ addq(R8, Immediate(2));
  __ sarq(R8, Immediate(2));
  __ decq(R8);  // R8 = number of digit pairs to process.

  // uint128_t c = high64(t)
  __ xorq(R13, R13);  // R13 = high64(c) == 0
  __ movq(R12, RDX);  // R12 = low64(c) == high64(t)

  Label loop, done;
  __ Bind(&loop);
  // x:   RBX
  // xip: RDI
  // ajp: RSI
  // c:   R13:R12
  // t:   RCX:RDX:RAX (not live at loop entry)
  // n:   R8

  // while (--n >= 0)
  __ decq(R8);  // --n
  __ j(NEGATIVE, &done, Assembler::kNearJump);

  // uint64_t xi = *xip++
  __ movq(RAX, Address(RDI, 0));
  __ addq(RDI, Immediate(2*Bigint::kBytesPerDigit));

  // uint192_t t = RCX:RDX:RAX = 2*x*xi + aj + c
  __ mulq(RBX);  // RDX:RAX = RAX * RBX
  __ xorq(RCX, RCX);  // RCX = 0
  __ shldq(RCX, RDX, Immediate(1));
  __ shldq(RDX, RAX, Immediate(1));
  __ shlq(RAX, Immediate(1));  // RCX:RDX:RAX <<= 1
  __ addq(RAX, Address(RSI, 0));  // t += aj
  __ adcq(RDX, Immediate(0));
  __ adcq(RCX, Immediate(0));
  __ addq(RAX, R12);  // t += low64(c)
  __ adcq(RDX, R13);  // t += high64(c) << 64
  __ adcq(RCX, Immediate(0));

  // *ajp++ = low64(t)
  __ movq(Address(RSI, 0), RAX);
  __ addq(RSI, Immediate(2*Bigint::kBytesPerDigit));

  // c = high128(t)
  __ movq(R12, RDX);
  __ movq(R13, RCX);

  __ jmp(&loop, Assembler::kNearJump);

  __ Bind(&done);
  // uint128_t t = aj + c
  __ addq(R12, Address(RSI, 0));  // t = c, t += *ajp
  __ adcq(R13, Immediate(0));

  // *ajp++ = low64(t)
  // *ajp = high64(t)
  __ movq(Address(RSI, 0), R12);
  __ movq(Address(RSI, 2*Bigint::kBytesPerDigit), R13);

  __ Bind(&x_zero);
  __ movq(RAX, Immediate(Smi::RawValue(2)));  // Two digits processed.
  __ ret();
}


void Intrinsifier::Bigint_estQuotientDigit(Assembler* assembler) {
  // Pseudo code:
  // static int _estQuotientDigit(Uint32List args, Uint32List digits, int i) {
  //   uint64_t yt = args[_YT_LO .. _YT];  // _YT_LO == 0, _YT == 1.
  //   uint64_t* dp = &digits[(i >> 1) - 1];  // i is Smi.
  //   uint64_t dh = dp[0];  // dh == digits[(i >> 1) - 1 .. i >> 1].
  //   uint64_t qd;
  //   if (dh == yt) {
  //     qd = (DIGIT_MASK << 32) | DIGIT_MASK;
  //   } else {
  //     dl = dp[-1];  // dl == digits[(i >> 1) - 3 .. (i >> 1) - 2].
  //     qd = dh:dl / yt;  // No overflow possible, because dh < yt.
  //   }
  //   args[_QD .. _QD_HI] = qd;  // _QD == 2, _QD_HI == 3.
  //   return 2;
  // }

  // RDI = args
  __ movq(RDI, Address(RSP, 3 * kWordSize));  // args

  // RCX = yt = args[0..1]
  __ movq(RCX, FieldAddress(RDI, TypedData::data_offset()));

  // RBX = dp = &digits[(i >> 1) - 1]
  __ movq(RBX, Address(RSP, 2 * kWordSize));  // digits
  __ movq(RAX, Address(RSP, 1 * kWordSize));  // i is Smi and odd.
  __ leaq(RBX, FieldAddress(RBX, RAX, TIMES_2,
                            TypedData::data_offset() - Bigint::kBytesPerDigit));

  // RDX = dh = dp[0]
  __ movq(RDX, Address(RBX, 0));

  // RAX = qd = (DIGIT_MASK << 32) | DIGIT_MASK = -1
  __ movq(RAX, Immediate(-1));

  // Return qd if dh == yt
  Label return_qd;
  __ cmpq(RDX, RCX);
  __ j(EQUAL, &return_qd, Assembler::kNearJump);

  // RAX = dl = dp[-1]
  __ movq(RAX, Address(RBX, -2*Bigint::kBytesPerDigit));

  // RAX = qd = dh:dl / yt = RDX:RAX / RCX
  __ divq(RCX);

  __ Bind(&return_qd);
  // args[2..3] = qd
  __ movq(FieldAddress(RDI,
                       TypedData::data_offset() + 2*Bigint::kBytesPerDigit),
          RAX);

  __ movq(RAX, Immediate(Smi::RawValue(2)));  // Two digits processed.
  __ ret();
}


void Intrinsifier::Montgomery_mulMod(Assembler* assembler) {
  // Pseudo code:
  // static int _mulMod(Uint32List args, Uint32List digits, int i) {
  //   uint64_t rho = args[_RHO .. _RHO_HI];  // _RHO == 2, _RHO_HI == 3.
  //   uint64_t d = digits[i >> 1 .. (i >> 1) + 1];  // i is Smi and even.
  //   uint128_t t = rho*d;
  //   args[_MU .. _MU_HI] = t mod DIGIT_BASE^2;  // _MU == 4, _MU_HI == 5.
  //   return 2;
  // }

  // RDI = args
  __ movq(RDI, Address(RSP, 3 * kWordSize));  // args

  // RCX = rho = args[2 .. 3]
  __ movq(RCX,
          FieldAddress(RDI,
                       TypedData::data_offset() + 2*Bigint::kBytesPerDigit));

  // RAX = digits[i >> 1 .. (i >> 1) + 1]
  __ movq(RBX, Address(RSP, 2 * kWordSize));  // digits
  __ movq(RAX, Address(RSP, 1 * kWordSize));  // i is Smi
  __ movq(RAX, FieldAddress(RBX, RAX, TIMES_2, TypedData::data_offset()));

  // RDX:RAX = t = rho*d
  __ mulq(RCX);

  // args[4 .. 5] = t mod DIGIT_BASE^2 = low64(t)
  __ movq(FieldAddress(RDI,
                       TypedData::data_offset() + 4*Bigint::kBytesPerDigit),
          RAX);

  __ movq(RAX, Immediate(Smi::RawValue(2)));  // Two digits processed.
  __ ret();
}


// Check if the last argument is a double, jump to label 'is_smi' if smi
// (easy to convert to double), otherwise jump to label 'not_double_smi',
// Returns the last argument in RAX.
static void TestLastArgumentIsDouble(Assembler* assembler,
                                     Label* is_smi,
                                     Label* not_double_smi) {
  __ movq(RAX, Address(RSP, + 1 * kWordSize));
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(ZERO, is_smi);  // Jump if Smi.
  __ CompareClassId(RAX, kDoubleCid);
  __ j(NOT_EQUAL, not_double_smi);
  // Fall through if double.
}


// Both arguments on stack, left argument is a double, right argument is of
// unknown type. Return true or false object in RAX. Any NaN argument
// returns false. Any non-double argument causes control flow to fall through
// to the slow case (compiled method body).
static void CompareDoubles(Assembler* assembler, Condition true_condition) {
  Label fall_through, is_false, is_true, is_smi, double_op;
  TestLastArgumentIsDouble(assembler, &is_smi, &fall_through);
  // Both arguments are double, right operand is in RAX.
  __ movsd(XMM1, FieldAddress(RAX, Double::value_offset()));
  __ Bind(&double_op);
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // Left argument.
  __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
  __ comisd(XMM0, XMM1);
  __ j(PARITY_EVEN, &is_false, Assembler::kNearJump);  // NaN -> false;
  __ j(true_condition, &is_true, Assembler::kNearJump);
  // Fall through false.
  __ Bind(&is_false);
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&is_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();
  __ Bind(&is_smi);
  __ SmiUntag(RAX);
  __ cvtsi2sdq(XMM1, RAX);
  __ jmp(&double_op);
  __ Bind(&fall_through);
}


void Intrinsifier::Double_greaterThan(Assembler* assembler) {
  CompareDoubles(assembler, ABOVE);
}


void Intrinsifier::Double_greaterEqualThan(Assembler* assembler) {
  CompareDoubles(assembler, ABOVE_EQUAL);
}


void Intrinsifier::Double_lessThan(Assembler* assembler) {
  CompareDoubles(assembler, BELOW);
}


void Intrinsifier::Double_equal(Assembler* assembler) {
  CompareDoubles(assembler, EQUAL);
}


void Intrinsifier::Double_lessEqualThan(Assembler* assembler) {
  CompareDoubles(assembler, BELOW_EQUAL);
}


// Expects left argument to be double (receiver). Right argument is unknown.
// Both arguments are on stack.
static void DoubleArithmeticOperations(Assembler* assembler, Token::Kind kind) {
  Label fall_through;
  TestLastArgumentIsDouble(assembler, &fall_through, &fall_through);
  // Both arguments are double, right operand is in RAX.
  __ movsd(XMM1, FieldAddress(RAX, Double::value_offset()));
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // Left argument.
  __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
  switch (kind) {
    case Token::kADD: __ addsd(XMM0, XMM1); break;
    case Token::kSUB: __ subsd(XMM0, XMM1); break;
    case Token::kMUL: __ mulsd(XMM0, XMM1); break;
    case Token::kDIV: __ divsd(XMM0, XMM1); break;
    default: UNREACHABLE();
  }
  const Class& double_class = Class::Handle(
      Isolate::Current()->object_store()->double_class());
  __ TryAllocate(double_class,
                 &fall_through,
                 Assembler::kFarJump,
                 RAX,  // Result register.
                 R13);
  __ movsd(FieldAddress(RAX, Double::value_offset()), XMM0);
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Double_add(Assembler* assembler) {
  DoubleArithmeticOperations(assembler, Token::kADD);
}


void Intrinsifier::Double_mul(Assembler* assembler) {
  DoubleArithmeticOperations(assembler, Token::kMUL);
}


void Intrinsifier::Double_sub(Assembler* assembler) {
  DoubleArithmeticOperations(assembler, Token::kSUB);
}


void Intrinsifier::Double_div(Assembler* assembler) {
  DoubleArithmeticOperations(assembler, Token::kDIV);
}


void Intrinsifier::Double_mulFromInteger(Assembler* assembler) {
  Label fall_through;
  // Only smis allowed.
  __ movq(RAX, Address(RSP, + 1 * kWordSize));
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);
  // Is Smi.
  __ SmiUntag(RAX);
  __ cvtsi2sdq(XMM1, RAX);
  __ movq(RAX, Address(RSP, + 2 * kWordSize));
  __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
  __ mulsd(XMM0, XMM1);
  const Class& double_class = Class::Handle(
      Isolate::Current()->object_store()->double_class());
  __ TryAllocate(double_class,
                 &fall_through,
                 Assembler::kFarJump,
                 RAX,  // Result register.
                 R13);
  __ movsd(FieldAddress(RAX, Double::value_offset()), XMM0);
  __ ret();
  __ Bind(&fall_through);
}


// Left is double right is integer (Bigint, Mint or Smi)
void Intrinsifier::DoubleFromInteger(Assembler* assembler) {
  Label fall_through;
  __ movq(RAX, Address(RSP, +1 * kWordSize));
  __ testq(RAX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);
  // Is Smi.
  __ SmiUntag(RAX);
  __ cvtsi2sdq(XMM0, RAX);
  const Class& double_class = Class::Handle(
      Isolate::Current()->object_store()->double_class());
  __ TryAllocate(double_class,
                 &fall_through,
                 Assembler::kFarJump,
                 RAX,  // Result register.
                 R13);
  __ movsd(FieldAddress(RAX, Double::value_offset()), XMM0);
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::Double_getIsNaN(Assembler* assembler) {
  Label is_true;
  __ movq(RAX, Address(RSP, +1 * kWordSize));
  __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
  __ comisd(XMM0, XMM0);
  __ j(PARITY_EVEN, &is_true, Assembler::kNearJump);  // NaN -> true;
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&is_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();
}


void Intrinsifier::Double_getIsNegative(Assembler* assembler) {
  Label is_false, is_true, is_zero;
  __ movq(RAX, Address(RSP, +1 * kWordSize));
  __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
  __ xorpd(XMM1, XMM1);  // 0.0 -> XMM1.
  __ comisd(XMM0, XMM1);
  __ j(PARITY_EVEN, &is_false, Assembler::kNearJump);  // NaN -> false.
  __ j(EQUAL, &is_zero, Assembler::kNearJump);  // Check for negative zero.
  __ j(ABOVE_EQUAL, &is_false, Assembler::kNearJump);  // >= 0 -> false.
  __ Bind(&is_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();
  __ Bind(&is_false);
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&is_zero);
  // Check for negative zero (get the sign bit).
  __ movmskpd(RAX, XMM0);
  __ testq(RAX, Immediate(1));
  __ j(NOT_ZERO, &is_true, Assembler::kNearJump);
  __ jmp(&is_false, Assembler::kNearJump);
}


void Intrinsifier::DoubleToInteger(Assembler* assembler) {
  __ movq(RAX, Address(RSP, +1 * kWordSize));
  __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
  __ cvttsd2siq(RAX, XMM0);
  // Overflow is signalled with minint.
  Label fall_through;
  // Check for overflow and that it fits into Smi.
  __ movq(RCX, RAX);
  __ shlq(RCX, Immediate(1));
  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
  __ SmiTag(RAX);
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::MathSqrt(Assembler* assembler) {
  Label fall_through, is_smi, double_op;
  TestLastArgumentIsDouble(assembler, &is_smi, &fall_through);
  // Argument is double and is in RAX.
  __ movsd(XMM1, FieldAddress(RAX, Double::value_offset()));
  __ Bind(&double_op);
  __ sqrtsd(XMM0, XMM1);
  const Class& double_class = Class::Handle(
      Isolate::Current()->object_store()->double_class());
  __ TryAllocate(double_class,
                 &fall_through,
                 Assembler::kFarJump,
                 RAX,  // Result register.
                 R13);
  __ movsd(FieldAddress(RAX, Double::value_offset()), XMM0);
  __ ret();
  __ Bind(&is_smi);
  __ SmiUntag(RAX);
  __ cvtsi2sdq(XMM1, RAX);
  __ jmp(&double_op);
  __ Bind(&fall_through);
}


//    var state = ((_A * (_state[kSTATE_LO])) + _state[kSTATE_HI]) & _MASK_64;
//    _state[kSTATE_LO] = state & _MASK_32;
//    _state[kSTATE_HI] = state >> 32;
void Intrinsifier::Random_nextState(Assembler* assembler) {
  const Library& math_lib = Library::Handle(Library::MathLibrary());
  ASSERT(!math_lib.IsNull());
  const Class& random_class = Class::Handle(
      math_lib.LookupClassAllowPrivate(Symbols::_Random()));
  ASSERT(!random_class.IsNull());
  const Field& state_field = Field::ZoneHandle(
      random_class.LookupInstanceField(Symbols::_state()));
  ASSERT(!state_field.IsNull());
  const Field& random_A_field = Field::ZoneHandle(
      random_class.LookupStaticField(Symbols::_A()));
  ASSERT(!random_A_field.IsNull());
  ASSERT(random_A_field.is_const());
  const Instance& a_value = Instance::Handle(random_A_field.StaticValue());
  const int64_t a_int_value = Integer::Cast(a_value).AsInt64Value();
  // Receiver.
  __ movq(RAX, Address(RSP, + 1 * kWordSize));
  // Field '_state'.
  __ movq(RBX, FieldAddress(RAX, state_field.Offset()));
  // Addresses of _state[0] and _state[1].
  const intptr_t scale = Instance::ElementSizeFor(kTypedDataUint32ArrayCid);
  const intptr_t offset = Instance::DataOffsetFor(kTypedDataUint32ArrayCid);
  Address addr_0 = FieldAddress(RBX, 0 * scale + offset);
  Address addr_1 = FieldAddress(RBX, 1 * scale + offset);
  __ movq(RAX, Immediate(a_int_value));
  __ movl(RCX, addr_0);
  __ imulq(RCX, RAX);
  __ movl(RDX, addr_1);
  __ addq(RDX, RCX);
  __ movl(addr_0, RDX);
  __ shrq(RDX, Immediate(32));
  __ movl(addr_1, RDX);
  __ ret();
}

// Identity comparison.
void Intrinsifier::ObjectEquals(Assembler* assembler) {
  Label is_true;
  const intptr_t kReceiverOffset = 2;
  const intptr_t kArgumentOffset = 1;

  __ movq(RAX, Address(RSP, + kArgumentOffset * kWordSize));
  __ cmpq(RAX, Address(RSP, + kReceiverOffset * kWordSize));
  __ j(EQUAL, &is_true, Assembler::kNearJump);
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&is_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();
}


// Return type quickly for simple types (not parameterized and not signature).
void Intrinsifier::ObjectRuntimeType(Assembler* assembler) {
  Label fall_through;
  __ movq(RAX, Address(RSP, + 1 * kWordSize));
  __ LoadClassIdMayBeSmi(RCX, RAX);

  // RCX: untagged cid of instance (RAX).
  __ LoadClassById(RDI, RCX);
  // RDI: class of instance (RAX).
  __ movq(RCX, FieldAddress(RDI, Class::signature_function_offset()));
  __ CompareObject(RCX, Object::null_object());
  __ j(NOT_EQUAL, &fall_through, Assembler::kNearJump);

  __ movzxw(RCX, FieldAddress(RDI, Class::num_type_arguments_offset()));
  __ cmpq(RCX, Immediate(0));
  __ j(NOT_EQUAL, &fall_through, Assembler::kNearJump);
  __ movq(RAX, FieldAddress(RDI, Class::canonical_types_offset()));
  __ CompareObject(RAX, Object::null_object());
  __ j(EQUAL, &fall_through, Assembler::kNearJump);  // Not yet set.
  __ ret();

  __ Bind(&fall_through);
}


void Intrinsifier::String_getHashCode(Assembler* assembler) {
  Label fall_through;
  __ movq(RAX, Address(RSP, + 1 * kWordSize));  // String object.
  __ movq(RAX, FieldAddress(RAX, String::hash_offset()));
  __ cmpq(RAX, Immediate(0));
  __ j(EQUAL, &fall_through, Assembler::kNearJump);
  __ ret();
  __ Bind(&fall_through);
  // Hash not yet computed.
}


void Intrinsifier::StringBaseCodeUnitAt(Assembler* assembler) {
  Label fall_through, try_two_byte_string;
  __ movq(RCX, Address(RSP, + 1 * kWordSize));  // Index.
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // String.
  __ testq(RCX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through, Assembler::kNearJump);  // Non-smi index.
  // Range check.
  __ cmpq(RCX, FieldAddress(RAX, String::length_offset()));
  // Runtime throws exception.
  __ j(ABOVE_EQUAL, &fall_through, Assembler::kNearJump);
  __ CompareClassId(RAX, kOneByteStringCid);
  __ j(NOT_EQUAL, &try_two_byte_string, Assembler::kNearJump);
  __ SmiUntag(RCX);
  __ movzxb(RAX, FieldAddress(RAX, RCX, TIMES_1, OneByteString::data_offset()));
  __ SmiTag(RAX);
  __ ret();

  __ Bind(&try_two_byte_string);
  __ CompareClassId(RAX, kTwoByteStringCid);
  __ j(NOT_EQUAL, &fall_through, Assembler::kNearJump);
  ASSERT(kSmiTagShift == 1);
  __ movzxw(RAX, FieldAddress(RAX, RCX, TIMES_1, OneByteString::data_offset()));
  __ SmiTag(RAX);
  __ ret();

  __ Bind(&fall_through);
}


void GenerateSubstringMatchesSpecialization(Assembler* assembler,
                                            intptr_t receiver_cid,
                                            intptr_t other_cid,
                                            Label* return_true,
                                            Label* return_false) {
  __ movq(R8, FieldAddress(RAX, String::length_offset()));
  __ movq(R9, FieldAddress(RCX, String::length_offset()));

  // if (other.length == 0) return true;
  __ testq(R9, R9);
  __ j(ZERO, return_true);

  // if (start < 0) return false;
  __ testq(RBX, RBX);
  __ j(SIGN, return_false);

  // if (start + other.length > this.length) return false;
  __ movq(R11, RBX);
  __ addq(R11, R9);
  __ cmpq(R11, R8);
  __ j(GREATER, return_false);

  __ SmiUntag(RBX);  // start
  __ SmiUntag(R9);   // other.length
  __ movq(R11, Immediate(0));  // i = 0

  // do
  Label loop;
  __ Bind(&loop);

  // this.codeUnitAt(i + start)
  // clobbering this.length
  __ movq(R8, R11);
  __ addq(R8, RBX);
  if (receiver_cid == kOneByteStringCid) {
    __ movzxb(R12,
              FieldAddress(RAX, R8, TIMES_1, OneByteString::data_offset()));
  } else {
    ASSERT(receiver_cid == kTwoByteStringCid);
    __ movzxw(R12,
              FieldAddress(RAX, R8, TIMES_2, TwoByteString::data_offset()));
  }
  // other.codeUnitAt(i)
  if (other_cid == kOneByteStringCid) {
    __ movzxb(R13,
              FieldAddress(RCX, R11, TIMES_1, OneByteString::data_offset()));
  } else {
    ASSERT(other_cid == kTwoByteStringCid);
    __ movzxw(R13,
              FieldAddress(RCX, R11, TIMES_2, TwoByteString::data_offset()));
  }
  __ cmpq(R12, R13);
  __ j(NOT_EQUAL, return_false);

  // i++, while (i < len)
  __ addq(R11, Immediate(1));
  __ cmpq(R11, R9);
  __ j(LESS, &loop, Assembler::kNearJump);

  __ jmp(return_true);
}


// bool _substringMatches(int start, String other)
// This intrinsic handles a OneByteString or TwoByteString receiver with a
// OneByteString other.
void Intrinsifier::StringBaseSubstringMatches(Assembler* assembler) {
  Label fall_through, return_true, return_false, try_two_byte;
  __ movq(RAX, Address(RSP, + 3 * kWordSize));  // receiver
  __ movq(RBX, Address(RSP, + 2 * kWordSize));  // start
  __ movq(RCX, Address(RSP, + 1 * kWordSize));  // other

  __ testq(RBX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);  // 'start' is not Smi.

  __ CompareClassId(RCX, kOneByteStringCid);
  __ j(NOT_EQUAL, &fall_through);

  __ CompareClassId(RAX, kOneByteStringCid);
  __ j(NOT_EQUAL, &try_two_byte);

  GenerateSubstringMatchesSpecialization(assembler,
                                         kOneByteStringCid,
                                         kOneByteStringCid,
                                         &return_true,
                                         &return_false);

  __ Bind(&try_two_byte);
  __ CompareClassId(RAX, kTwoByteStringCid);
  __ j(NOT_EQUAL, &fall_through);

  GenerateSubstringMatchesSpecialization(assembler,
                                         kTwoByteStringCid,
                                         kOneByteStringCid,
                                         &return_true,
                                         &return_false);

  __ Bind(&return_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();

  __ Bind(&return_false);
  __ LoadObject(RAX, Bool::False());
  __ ret();

  __ Bind(&fall_through);
}


void Intrinsifier::StringBaseCharAt(Assembler* assembler) {
  Label fall_through, try_two_byte_string;
  __ movq(RCX, Address(RSP, + 1 * kWordSize));  // Index.
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // String.
  __ testq(RCX, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);  // Non-smi index.
  // Range check.
  __ cmpq(RCX, FieldAddress(RAX, String::length_offset()));
  // Runtime throws exception.
  __ j(ABOVE_EQUAL, &fall_through);
  __ CompareClassId(RAX, kOneByteStringCid);
  __ j(NOT_EQUAL, &try_two_byte_string, Assembler::kNearJump);
  __ SmiUntag(RCX);
  __ movzxb(RCX, FieldAddress(RAX, RCX, TIMES_1, OneByteString::data_offset()));
  __ cmpq(RCX, Immediate(Symbols::kNumberOfOneCharCodeSymbols));
  __ j(GREATER_EQUAL, &fall_through);
  __ movq(RAX, Address(THR, Thread::predefined_symbols_address_offset()));
  __ movq(RAX, Address(RAX,
                       RCX,
                       TIMES_8,
                       Symbols::kNullCharCodeSymbolOffset * kWordSize));
  __ ret();

  __ Bind(&try_two_byte_string);
  __ CompareClassId(RAX, kTwoByteStringCid);
  __ j(NOT_EQUAL, &fall_through);
  ASSERT(kSmiTagShift == 1);
  __ movzxw(RCX, FieldAddress(RAX, RCX, TIMES_1, OneByteString::data_offset()));
  __ cmpq(RCX, Immediate(Symbols::kNumberOfOneCharCodeSymbols));
  __ j(GREATER_EQUAL, &fall_through);
  __ movq(RAX, Address(THR, Thread::predefined_symbols_address_offset()));
  __ movq(RAX, Address(RAX,
                       RCX,
                       TIMES_8,
                       Symbols::kNullCharCodeSymbolOffset * kWordSize));
  __ ret();

  __ Bind(&fall_through);
}


void Intrinsifier::StringBaseIsEmpty(Assembler* assembler) {
  Label is_true;
  // Get length.
  __ movq(RAX, Address(RSP, + 1 * kWordSize));  // String object.
  __ movq(RAX, FieldAddress(RAX, String::length_offset()));
  __ cmpq(RAX, Immediate(Smi::RawValue(0)));
  __ j(EQUAL, &is_true, Assembler::kNearJump);
  __ LoadObject(RAX, Bool::False());
  __ ret();
  __ Bind(&is_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();
}


void Intrinsifier::OneByteString_getHashCode(Assembler* assembler) {
  Label compute_hash;
  __ movq(RBX, Address(RSP, + 1 * kWordSize));  // OneByteString object.
  __ movq(RAX, FieldAddress(RBX, String::hash_offset()));
  __ cmpq(RAX, Immediate(0));
  __ j(EQUAL, &compute_hash, Assembler::kNearJump);
  __ ret();

  __ Bind(&compute_hash);
  // Hash not yet computed, use algorithm of class StringHasher.
  __ movq(RCX, FieldAddress(RBX, String::length_offset()));
  __ SmiUntag(RCX);
  __ xorq(RAX, RAX);
  __ xorq(RDI, RDI);
  // RBX: Instance of OneByteString.
  // RCX: String length, untagged integer.
  // RDI: Loop counter, untagged integer.
  // RAX: Hash code, untagged integer.
  Label loop, done, set_hash_code;
  __ Bind(&loop);
  __ cmpq(RDI, RCX);
  __ j(EQUAL, &done, Assembler::kNearJump);
  // Add to hash code: (hash_ is uint32)
  // hash_ += ch;
  // hash_ += hash_ << 10;
  // hash_ ^= hash_ >> 6;
  // Get one characters (ch).
  __ movzxb(RDX, FieldAddress(RBX, RDI, TIMES_1, OneByteString::data_offset()));
  // RDX: ch and temporary.
  __ addl(RAX, RDX);
  __ movq(RDX, RAX);
  __ shll(RDX, Immediate(10));
  __ addl(RAX, RDX);
  __ movq(RDX, RAX);
  __ shrl(RDX, Immediate(6));
  __ xorl(RAX, RDX);

  __ incq(RDI);
  __ jmp(&loop, Assembler::kNearJump);

  __ Bind(&done);
  // Finalize:
  // hash_ += hash_ << 3;
  // hash_ ^= hash_ >> 11;
  // hash_ += hash_ << 15;
  __ movq(RDX, RAX);
  __ shll(RDX, Immediate(3));
  __ addl(RAX, RDX);
  __ movq(RDX, RAX);
  __ shrl(RDX, Immediate(11));
  __ xorl(RAX, RDX);
  __ movq(RDX, RAX);
  __ shll(RDX, Immediate(15));
  __ addl(RAX, RDX);
  // hash_ = hash_ & ((static_cast<intptr_t>(1) << bits) - 1);
  __ andl(RAX,
      Immediate(((static_cast<intptr_t>(1) << String::kHashBits) - 1)));

  // return hash_ == 0 ? 1 : hash_;
  __ cmpq(RAX, Immediate(0));
  __ j(NOT_EQUAL, &set_hash_code, Assembler::kNearJump);
  __ incq(RAX);
  __ Bind(&set_hash_code);
  __ SmiTag(RAX);
  __ StoreIntoSmiField(FieldAddress(RBX, String::hash_offset()), RAX);
  __ ret();
}


// Allocates one-byte string of length 'end - start'. The content is not
// initialized. 'length-reg' contains tagged length.
// Returns new string as tagged pointer in RAX.
static void TryAllocateOnebyteString(Assembler* assembler,
                                     Label* ok,
                                     Label* failure,
                                     Register length_reg) {
  __ MaybeTraceAllocation(kOneByteStringCid, failure, false,
                          /* inline_isolate = */ false);
  if (length_reg != RDI) {
    __ movq(RDI, length_reg);
  }
  Label pop_and_fail;
  __ pushq(RDI);  // Preserve length.
  __ SmiUntag(RDI);
  const intptr_t fixed_size = sizeof(RawString) + kObjectAlignment - 1;
  __ leaq(RDI, Address(RDI, TIMES_1, fixed_size));  // RDI is a Smi.
  __ andq(RDI, Immediate(-kObjectAlignment));

  const intptr_t cid = kOneByteStringCid;
  Heap::Space space = Heap::SpaceForAllocation(cid);
  __ movq(R13, Address(THR, Thread::heap_offset()));
  __ movq(RAX, Address(R13, Heap::TopOffset(space)));

  // RDI: allocation size.
  __ movq(RCX, RAX);
  __ addq(RCX, RDI);
  __ j(CARRY,  &pop_and_fail);

  // Check if the allocation fits into the remaining space.
  // RAX: potential new object start.
  // RCX: potential next object start.
  // RDI: allocation size.
  // R13: heap.
  __ cmpq(RCX, Address(R13, Heap::EndOffset(space)));
  __ j(ABOVE_EQUAL, &pop_and_fail);

  // Successfully allocated the object(s), now update top to point to
  // next object start and initialize the object.
  __ movq(Address(R13, Heap::TopOffset(space)), RCX);
  __ addq(RAX, Immediate(kHeapObjectTag));
  __ UpdateAllocationStatsWithSize(cid, RDI, space,
                                   /* inline_isolate = */ false);

  // Initialize the tags.
  // RAX: new object start as a tagged pointer.
  // RDI: allocation size.
  {
    Label size_tag_overflow, done;
    __ cmpq(RDI, Immediate(RawObject::SizeTag::kMaxSizeTag));
    __ j(ABOVE, &size_tag_overflow, Assembler::kNearJump);
    __ shlq(RDI, Immediate(RawObject::kSizeTagPos - kObjectAlignmentLog2));
    __ jmp(&done, Assembler::kNearJump);

    __ Bind(&size_tag_overflow);
    __ xorq(RDI, RDI);
    __ Bind(&done);

    // Get the class index and insert it into the tags.
    __ orq(RDI, Immediate(RawObject::ClassIdTag::encode(cid)));
    __ movq(FieldAddress(RAX, String::tags_offset()), RDI);  // Tags.
  }

  // Set the length field.
  __ popq(RDI);
  __ InitializeFieldNoBarrier(RAX,
                              FieldAddress(RAX, String::length_offset()),
                              RDI);
  // Clear hash.
  __ ZeroInitSmiField(FieldAddress(RAX, String::hash_offset()));
  __ jmp(ok, Assembler::kNearJump);

  __ Bind(&pop_and_fail);
  __ popq(RDI);
  __ jmp(failure);
}


// Arg0: OneByteString (receiver).
// Arg1: Start index as Smi.
// Arg2: End index as Smi.
// The indexes must be valid.
void Intrinsifier::OneByteString_substringUnchecked(Assembler* assembler) {
  const intptr_t kStringOffset = 3 * kWordSize;
  const intptr_t kStartIndexOffset = 2 * kWordSize;
  const intptr_t kEndIndexOffset = 1 * kWordSize;
  Label fall_through, ok;
  __ movq(RSI, Address(RSP, + kStartIndexOffset));
  __ movq(RDI, Address(RSP, + kEndIndexOffset));
  __ orq(RSI, RDI);
  __ testq(RSI, Immediate(kSmiTagMask));
  __ j(NOT_ZERO, &fall_through);  // 'start', 'end' not Smi.

  __ subq(RDI, Address(RSP, + kStartIndexOffset));
  TryAllocateOnebyteString(assembler, &ok, &fall_through, RDI);
  __ Bind(&ok);
  // RAX: new string as tagged pointer.
  // Copy string.
  __ movq(RSI, Address(RSP, + kStringOffset));
  __ movq(RBX, Address(RSP, + kStartIndexOffset));
  __ SmiUntag(RBX);
  __ leaq(RSI, FieldAddress(RSI, RBX, TIMES_1, OneByteString::data_offset()));
  // RSI: Start address to copy from (untagged).
  // RBX: Untagged start index.
  __ movq(RCX, Address(RSP, + kEndIndexOffset));
  __ SmiUntag(RCX);
  __ subq(RCX, RBX);
  __ xorq(RDX, RDX);
  // RSI: Start address to copy from (untagged).
  // RCX: Untagged number of bytes to copy.
  // RAX: Tagged result string
  // RDX: Loop counter.
  // RBX: Scratch register.
  Label loop, check;
  __ jmp(&check, Assembler::kNearJump);
  __ Bind(&loop);
  __ movzxb(RBX, Address(RSI, RDX, TIMES_1, 0));
  __ movb(FieldAddress(RAX, RDX, TIMES_1, OneByteString::data_offset()), RBX);
  __ incq(RDX);
  __ Bind(&check);
  __ cmpq(RDX, RCX);
  __ j(LESS, &loop, Assembler::kNearJump);
  __ ret();
  __ Bind(&fall_through);
}


void Intrinsifier::OneByteStringSetAt(Assembler* assembler) {
  __ movq(RCX, Address(RSP, + 1 * kWordSize));  // Value.
  __ movq(RBX, Address(RSP, + 2 * kWordSize));  // Index.
  __ movq(RAX, Address(RSP, + 3 * kWordSize));  // OneByteString.
  __ SmiUntag(RBX);
  __ SmiUntag(RCX);
  __ movb(FieldAddress(RAX, RBX, TIMES_1, OneByteString::data_offset()), RCX);
  __ ret();
}


void Intrinsifier::OneByteString_allocate(Assembler* assembler) {
  __ movq(RDI, Address(RSP, + 1 * kWordSize));  // Length.v=
  Label fall_through, ok;
  TryAllocateOnebyteString(assembler, &ok, &fall_through, RDI);
  // RDI: Start address to copy from (untagged).

  __ Bind(&ok);
  __ ret();

  __ Bind(&fall_through);
}


// TODO(srdjan): Add combinations (one-byte/two-byte/external strings).
static void StringEquality(Assembler* assembler, intptr_t string_cid) {
  Label fall_through, is_true, is_false, loop;
  __ movq(RAX, Address(RSP, + 2 * kWordSize));  // This.
  __ movq(RCX, Address(RSP, + 1 * kWordSize));  // Other.

  // Are identical?
  __ cmpq(RAX, RCX);
  __ j(EQUAL, &is_true, Assembler::kNearJump);

  // Is other OneByteString?
  __ testq(RCX, Immediate(kSmiTagMask));
  __ j(ZERO, &is_false);  // Smi
  __ CompareClassId(RCX, string_cid);
  __ j(NOT_EQUAL, &fall_through, Assembler::kNearJump);

  // Have same length?
  __ movq(RDI, FieldAddress(RAX, String::length_offset()));
  __ cmpq(RDI, FieldAddress(RCX, String::length_offset()));
  __ j(NOT_EQUAL, &is_false, Assembler::kNearJump);

  // Check contents, no fall-through possible.
  // TODO(srdjan): write a faster check.
  __ SmiUntag(RDI);
  __ Bind(&loop);
  __ decq(RDI);
  __ cmpq(RDI, Immediate(0));
  __ j(LESS, &is_true, Assembler::kNearJump);
  if (string_cid == kOneByteStringCid) {
    __ movzxb(RBX,
        FieldAddress(RAX, RDI, TIMES_1, OneByteString::data_offset()));
    __ movzxb(RDX,
        FieldAddress(RCX, RDI, TIMES_1, OneByteString::data_offset()));
  } else if (string_cid == kTwoByteStringCid) {
    __ movzxw(RBX,
        FieldAddress(RAX, RDI, TIMES_2, TwoByteString::data_offset()));
    __ movzxw(RDX,
        FieldAddress(RCX, RDI, TIMES_2, TwoByteString::data_offset()));
  } else {
    UNIMPLEMENTED();
  }
  __ cmpq(RBX, RDX);
  __ j(NOT_EQUAL, &is_false, Assembler::kNearJump);
  __ jmp(&loop, Assembler::kNearJump);

  __ Bind(&is_true);
  __ LoadObject(RAX, Bool::True());
  __ ret();

  __ Bind(&is_false);
  __ LoadObject(RAX, Bool::False());
  __ ret();

  __ Bind(&fall_through);
}


void Intrinsifier::OneByteString_equality(Assembler* assembler) {
  StringEquality(assembler, kOneByteStringCid);
}


void Intrinsifier::TwoByteString_equality(Assembler* assembler) {
  StringEquality(assembler, kTwoByteStringCid);
}


void Intrinsifier::JSRegExp_ExecuteMatch(Assembler* assembler) {
  if (FLAG_interpret_irregexp) return;

  static const intptr_t kRegExpParamOffset = 3 * kWordSize;
  static const intptr_t kStringParamOffset = 2 * kWordSize;
  // start_index smi is located at offset 1.

  // Incoming registers:
  // RAX: Function. (Will be loaded with the specialized matcher function.)
  // RCX: Unknown. (Must be GC safe on tail call.)
  // R10: Arguments descriptor. (Will be preserved.)

  // Load the specialized function pointer into RAX. Leverage the fact the
  // string CIDs as well as stored function pointers are in sequence.
  __ movq(RBX, Address(RSP, kRegExpParamOffset));
  __ movq(RDI, Address(RSP, kStringParamOffset));
  __ LoadClassId(RDI, RDI);
  __ SubImmediate(RDI, Immediate(kOneByteStringCid));
  __ movq(RAX, FieldAddress(RBX, RDI, TIMES_8,
                            JSRegExp::function_offset(kOneByteStringCid)));

  // Registers are now set up for the lazy compile stub. It expects the function
  // in RAX, the argument descriptor in R10, and IC-Data in RCX.
  __ xorq(RCX, RCX);

  // Tail-call the function.
  __ movq(CODE_REG, FieldAddress(RAX, Function::code_offset()));
  __ movq(RDI, FieldAddress(RAX, Function::entry_point_offset()));
  __ jmp(RDI);
}


// On stack: user tag (+1), return-address (+0).
void Intrinsifier::UserTag_makeCurrent(Assembler* assembler) {
  // RBX: Isolate.
  __ LoadIsolate(RBX);
  // RAX: Current user tag.
  __ movq(RAX, Address(RBX, Isolate::current_tag_offset()));
  // R10: UserTag.
  __ movq(R10, Address(RSP, + 1 * kWordSize));
  // Set Isolate::current_tag_.
  __ movq(Address(RBX, Isolate::current_tag_offset()), R10);
  // R10: UserTag's tag.
  __ movq(R10, FieldAddress(R10, UserTag::tag_offset()));
  // Set Isolate::user_tag_.
  __ movq(Address(RBX, Isolate::user_tag_offset()), R10);
  __ ret();
}


void Intrinsifier::UserTag_defaultTag(Assembler* assembler) {
  __ LoadIsolate(RAX);
  __ movq(RAX, Address(RAX, Isolate::default_tag_offset()));
  __ ret();
}


void Intrinsifier::Profiler_getCurrentTag(Assembler* assembler) {
  __ LoadIsolate(RAX);
  __ movq(RAX, Address(RAX, Isolate::current_tag_offset()));
  __ ret();
}

#undef __

}  // namespace dart

#endif  // defined TARGET_ARCH_X64