asm_intrinsifier_arm.cc

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// Copyright (c) 2019, 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_ARM.
#if defined(TARGET_ARCH_ARM)
 
#define SHOULD_NOT_INCLUDE_RUNTIME
 
#include "vm/class_id.h"
#include "vm/compiler/asm_intrinsifier.h"
#include "vm/compiler/assembler/assembler.h"
 
namespace dart {
namespace compiler {
 
// When entering intrinsics code:
// PP: Caller's ObjectPool in JIT / global ObjectPool in AOT
// CODE_REG: Callee's Code in JIT / not passed in AOT
// R4: Arguments descriptor
// LR: Return address
// The R4 and CODE_REG registers can be destroyed only if there is no slow-path,
// i.e. if the intrinsified method always executes a return.
// The FP register should not be modified, because it is used by the profiler.
// The PP and THR registers (see constants_arm.h) must be preserved.
 
#define __ assembler->
 
// Loads args from stack into R0 and R1
// Tests if they are smis, jumps to label not_smi if not.
static void TestBothArgumentsSmis(Assembler* assembler, Label* not_smi) {
  __ ldr(R0, Address(SP, +0 * target::kWordSize));
  __ ldr(R1, Address(SP, +1 * target::kWordSize));
  __ orr(TMP, R0, Operand(R1));
  __ tst(TMP, Operand(kSmiTagMask));
  __ b(not_smi, NE);
}
 
void AsmIntrinsifier::Integer_shl(Assembler* assembler, Label* normal_ir_body) {
  ASSERT(kSmiTagShift == 1);
  ASSERT(kSmiTag == 0);
  TestBothArgumentsSmis(assembler, normal_ir_body);
  __ CompareImmediate(R0, target::ToRawSmi(target::kSmiBits));
  __ b(normal_ir_body, HI);
 
  __ SmiUntag(R0);
 
  // Check for overflow by shifting left and shifting back arithmetically.
  // If the result is different from the original, there was overflow.
  __ mov(IP, Operand(R1, LSL, R0));
  __ cmp(R1, Operand(IP, ASR, R0));
 
  // No overflow, result in R0.
  __ mov(R0, Operand(R1, LSL, R0), EQ);
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, EQ));
  // Arguments are Smi but the shift produced an overflow to Mint.
  __ CompareImmediate(R1, 0);
  __ b(normal_ir_body, LT);
  __ SmiUntag(R1);
 
  // Pull off high bits that will be shifted off of R1 by making a mask
  // ((1 << R0) - 1), shifting it to the left, masking R1, then shifting back.
  // high bits = (((1 << R0) - 1) << (32 - R0)) & R1) >> (32 - R0)
  // lo bits = R1 << R0
  __ LoadImmediate(R8, 1);
  __ mov(R8, Operand(R8, LSL, R0));  // R8 <- 1 << R0
  __ sub(R8, R8, Operand(1));        // R8 <- R8 - 1
  __ rsb(R3, R0, Operand(32));       // R3 <- 32 - R0
  __ mov(R8, Operand(R8, LSL, R3));  // R8 <- R8 << R3
  __ and_(R8, R1, Operand(R8));      // R8 <- R8 & R1
  __ mov(R8, Operand(R8, LSR, R3));  // R8 <- R8 >> R3
  // Now R8 has the bits that fall off of R1 on a left shift.
  __ mov(R1, Operand(R1, LSL, R0));  // R1 gets the low bits.
 
  const Class& mint_class = MintClass();
  __ TryAllocate(mint_class, normal_ir_body, Assembler::kFarJump, R0, R2);
 
  __ str(R1, FieldAddress(R0, target::Mint::value_offset()));
  __ str(R8,
         FieldAddress(R0, target::Mint::value_offset() + target::kWordSize));
  __ Ret();
  __ Bind(normal_ir_body);
}
 
static void Get64SmiOrMint(Assembler* assembler,
                           Register res_hi,
                           Register res_lo,
                           Register reg,
                           Label* not_smi_or_mint) {
  Label not_smi, done;
  __ tst(reg, Operand(kSmiTagMask));
  __ b(&not_smi, NE);
  __ SmiUntag(reg);
 
  // Sign extend to 64 bit
  __ mov(res_lo, Operand(reg));
  __ mov(res_hi, Operand(res_lo, ASR, 31));
  __ b(&done);
 
  __ Bind(&not_smi);
  __ CompareClassId(reg, kMintCid, res_lo);
  __ b(not_smi_or_mint, NE);
 
  // Mint.
  __ ldr(res_lo, FieldAddress(reg, target::Mint::value_offset()));
  __ ldr(res_hi,
         FieldAddress(reg, target::Mint::value_offset() + target::kWordSize));
  __ Bind(&done);
}
 
static void CompareIntegers(Assembler* assembler,
                            Label* normal_ir_body,
                            Condition true_condition) {
  Label try_mint_smi, is_true, is_false, drop_two_fall_through, fall_through;
  TestBothArgumentsSmis(assembler, &try_mint_smi);
  // R0 contains the right argument. R1 contains left argument
 
  __ cmp(R1, Operand(R0));
  __ b(&is_true, true_condition);
  __ Bind(&is_false);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
  __ Bind(&is_true);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  // 64-bit comparison
  Condition hi_true_cond, hi_false_cond, lo_false_cond;
  switch (true_condition) {
    case LT:
    case LE:
      hi_true_cond = LT;
      hi_false_cond = GT;
      lo_false_cond = (true_condition == LT) ? CS : HI;
      break;
    case GT:
    case GE:
      hi_true_cond = GT;
      hi_false_cond = LT;
      lo_false_cond = (true_condition == GT) ? LS : CC;
      break;
    default:
      UNREACHABLE();
      hi_true_cond = hi_false_cond = lo_false_cond = VS;
  }
 
  __ Bind(&try_mint_smi);
  // Get left as 64 bit integer.
  Get64SmiOrMint(assembler, R3, R2, R1, normal_ir_body);
  // Get right as 64 bit integer.
  Get64SmiOrMint(assembler, R1, R8, R0, normal_ir_body);
  // R3: left high.
  // R2: left low.
  // R1: right high.
  // R8: right low.
 
  __ cmp(R3, Operand(R1));  // Compare left hi, right high.
  __ b(&is_false, hi_false_cond);
  __ b(&is_true, hi_true_cond);
  __ cmp(R2, Operand(R8));  // Compare left lo, right lo.
  __ b(&is_false, lo_false_cond);
  // Else is true.
  __ b(&is_true);
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::Integer_lessThan(Assembler* assembler,
                                       Label* normal_ir_body) {
  CompareIntegers(assembler, normal_ir_body, LT);
}
 
void AsmIntrinsifier::Integer_greaterThan(Assembler* assembler,
                                          Label* normal_ir_body) {
  CompareIntegers(assembler, normal_ir_body, GT);
}
 
void AsmIntrinsifier::Integer_lessEqualThan(Assembler* assembler,
                                            Label* normal_ir_body) {
  CompareIntegers(assembler, normal_ir_body, LE);
}
 
void AsmIntrinsifier::Integer_greaterEqualThan(Assembler* assembler,
                                               Label* normal_ir_body) {
  CompareIntegers(assembler, normal_ir_body, GE);
}
 
// This is called for Smi and Mint receivers. The right argument
// can be Smi, Mint or double.
void AsmIntrinsifier::Integer_equalToInteger(Assembler* assembler,
                                             Label* normal_ir_body) {
  Label true_label, check_for_mint;
  // For integer receiver '===' check first.
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ ldr(R1, Address(SP, 1 * target::kWordSize));
  __ cmp(R0, Operand(R1));
  __ b(&true_label, EQ);
 
  __ orr(R2, R0, Operand(R1));
  __ tst(R2, Operand(kSmiTagMask));
  __ b(&check_for_mint, NE);  // If R0 or R1 is not a smi do Mint checks.
 
  // Both arguments are smi, '===' is good enough.
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
  __ Bind(&true_label);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  // At least one of the arguments was not Smi.
  Label receiver_not_smi;
  __ Bind(&check_for_mint);
 
  __ tst(R1, Operand(kSmiTagMask));  // Check receiver.
  __ b(&receiver_not_smi, NE);
 
  // Left (receiver) is Smi, return false if right is not Double.
  // Note that an instance of Mint never contains a value that can be
  // represented by Smi.
 
  __ CompareClassId(R0, kDoubleCid, R2);
  __ b(normal_ir_body, EQ);
  __ LoadObject(R0,
                CastHandle<Object>(FalseObject()));  // Smi == Mint -> false.
  __ Ret();
 
  __ Bind(&receiver_not_smi);
  // R1:: receiver.
 
  __ CompareClassId(R1, kMintCid, R2);
  __ b(normal_ir_body, NE);
  // Receiver is Mint, return false if right is Smi.
  __ tst(R0, Operand(kSmiTagMask));
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), EQ);
  READS_RETURN_ADDRESS_FROM_LR(
      __ bx(LR, EQ));  // TODO(srdjan): Implement Mint == Mint comparison.
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::Integer_equal(Assembler* assembler,
                                    Label* normal_ir_body) {
  Integer_equalToInteger(assembler, normal_ir_body);
}
 
void AsmIntrinsifier::Smi_bitLength(Assembler* assembler,
                                    Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ SmiUntag(R0);
  // XOR with sign bit to complement bits if value is negative.
  __ eor(R0, R0, Operand(R0, ASR, 31));
  __ clz(R0, R0);
  __ rsb(R0, R0, Operand(32));
  __ SmiTag(R0);
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_lsh(Assembler* assembler, Label* normal_ir_body) {
  // static void _lsh(Uint32List x_digits, int x_used, int n,
  //                  Uint32List r_digits)
 
  // R0 = x_used, R1 = x_digits, x_used > 0, x_used is Smi.
  __ ldrd(R0, R1, SP, 2 * target::kWordSize);
  // R2 = r_digits, R3 = n, n is Smi, n % _DIGIT_BITS != 0.
  __ ldrd(R2, R3, SP, 0 * target::kWordSize);
  __ SmiUntag(R3);
  // R4 = n ~/ _DIGIT_BITS
  __ Asr(R4, R3, Operand(5));
  // R8 = &x_digits[0]
  __ add(R8, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
  // R6 = &r_digits[1]
  __ add(R6, R2,
         Operand(target::TypedData::payload_offset() - kHeapObjectTag +
                 kBytesPerBigIntDigit));
  // R2 = &x_digits[x_used]
  __ add(R2, R8, Operand(R0, LSL, 1));
  // R6 = &r_digits[x_used + n ~/ _DIGIT_BITS + 1]
  __ add(R4, R4, Operand(R0, ASR, 1));
  __ add(R6, R6, Operand(R4, LSL, 2));
  // R1 = n % _DIGIT_BITS
  __ and_(R1, R3, Operand(31));
  // R0 = 32 - R1
  __ rsb(R0, R1, Operand(32));
  __ mov(R9, Operand(0));
  Label loop;
  __ Bind(&loop);
  __ ldr(R4, Address(R2, -kBytesPerBigIntDigit, Address::PreIndex));
  __ orr(R9, R9, Operand(R4, LSR, R0));
  __ str(R9, Address(R6, -kBytesPerBigIntDigit, Address::PreIndex));
  __ mov(R9, Operand(R4, LSL, R1));
  __ teq(R2, Operand(R8));
  __ b(&loop, NE);
  __ str(R9, Address(R6, -kBytesPerBigIntDigit, Address::PreIndex));
  __ LoadObject(R0, NullObject());
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_rsh(Assembler* assembler, Label* normal_ir_body) {
  // static void _lsh(Uint32List x_digits, int x_used, int n,
  //                  Uint32List r_digits)
 
  // R0 = x_used, R1 = x_digits, x_used > 0, x_used is Smi.
  __ ldrd(R0, R1, SP, 2 * target::kWordSize);
  // R2 = r_digits, R3 = n, n is Smi, n % _DIGIT_BITS != 0.
  __ ldrd(R2, R3, SP, 0 * target::kWordSize);
  __ SmiUntag(R3);
  // R4 = n ~/ _DIGIT_BITS
  __ Asr(R4, R3, Operand(5));
  // R6 = &r_digits[0]
  __ add(R6, R2, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
  // R2 = &x_digits[n ~/ _DIGIT_BITS]
  __ add(R2, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
  __ add(R2, R2, Operand(R4, LSL, 2));
  // R8 = &r_digits[x_used - n ~/ _DIGIT_BITS - 1]
  __ add(R4, R4, Operand(1));
  __ rsb(R4, R4, Operand(R0, ASR, 1));
  __ add(R8, R6, Operand(R4, LSL, 2));
  // R1 = n % _DIGIT_BITS
  __ and_(R1, R3, Operand(31));
  // R0 = 32 - R1
  __ rsb(R0, R1, Operand(32));
  // R9 = x_digits[n ~/ _DIGIT_BITS] >> (n % _DIGIT_BITS)
  __ ldr(R9, Address(R2, kBytesPerBigIntDigit, Address::PostIndex));
  __ mov(R9, Operand(R9, LSR, R1));
  Label loop_entry;
  __ b(&loop_entry);
  Label loop;
  __ Bind(&loop);
  __ ldr(R4, Address(R2, kBytesPerBigIntDigit, Address::PostIndex));
  __ orr(R9, R9, Operand(R4, LSL, R0));
  __ str(R9, Address(R6, kBytesPerBigIntDigit, Address::PostIndex));
  __ mov(R9, Operand(R4, LSR, R1));
  __ Bind(&loop_entry);
  __ teq(R6, Operand(R8));
  __ b(&loop, NE);
  __ str(R9, Address(R6, 0));
  __ LoadObject(R0, NullObject());
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_absAdd(Assembler* assembler,
                                    Label* normal_ir_body) {
  // static void _absAdd(Uint32List digits, int used,
  //                     Uint32List a_digits, int a_used,
  //                     Uint32List r_digits)
 
  // R0 = used, R1 = digits
  __ ldrd(R0, R1, SP, 3 * target::kWordSize);
  // R1 = &digits[0]
  __ add(R1, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R2 = a_used, R3 = a_digits
  __ ldrd(R2, R3, SP, 1 * target::kWordSize);
  // R3 = &a_digits[0]
  __ add(R3, R3, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R8 = r_digits
  __ ldr(R8, Address(SP, 0 * target::kWordSize));
  // R8 = &r_digits[0]
  __ add(R8, R8, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R2 = &digits[a_used >> 1], a_used is Smi.
  __ add(R2, R1, Operand(R2, LSL, 1));
 
  // R6 = &digits[used >> 1], used is Smi.
  __ add(R6, R1, Operand(R0, LSL, 1));
 
  __ adds(R4, R4, Operand(0));  // carry flag = 0
  Label add_loop;
  __ Bind(&add_loop);
  // Loop a_used times, a_used > 0.
  __ ldr(R4, Address(R1, kBytesPerBigIntDigit, Address::PostIndex));
  __ ldr(R9, Address(R3, kBytesPerBigIntDigit, Address::PostIndex));
  __ adcs(R4, R4, Operand(R9));
  __ teq(R1, Operand(R2));  // Does not affect carry flag.
  __ str(R4, Address(R8, kBytesPerBigIntDigit, Address::PostIndex));
  __ b(&add_loop, NE);
 
  Label last_carry;
  __ teq(R1, Operand(R6));  // Does not affect carry flag.
  __ b(&last_carry, EQ);    // If used - a_used == 0.
 
  Label carry_loop;
  __ Bind(&carry_loop);
  // Loop used - a_used times, used - a_used > 0.
  __ ldr(R4, Address(R1, kBytesPerBigIntDigit, Address::PostIndex));
  __ adcs(R4, R4, Operand(0));
  __ teq(R1, Operand(R6));  // Does not affect carry flag.
  __ str(R4, Address(R8, kBytesPerBigIntDigit, Address::PostIndex));
  __ b(&carry_loop, NE);
 
  __ Bind(&last_carry);
  __ mov(R4, Operand(0));
  __ adc(R4, R4, Operand(0));
  __ str(R4, Address(R8, 0));
 
  __ LoadObject(R0, NullObject());
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_absSub(Assembler* assembler,
                                    Label* normal_ir_body) {
  // static void _absSub(Uint32List digits, int used,
  //                     Uint32List a_digits, int a_used,
  //                     Uint32List r_digits)
 
  // R0 = used, R1 = digits
  __ ldrd(R0, R1, SP, 3 * target::kWordSize);
  // R1 = &digits[0]
  __ add(R1, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R2 = a_used, R3 = a_digits
  __ ldrd(R2, R3, SP, 1 * target::kWordSize);
  // R3 = &a_digits[0]
  __ add(R3, R3, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R8 = r_digits
  __ ldr(R8, Address(SP, 0 * target::kWordSize));
  // R8 = &r_digits[0]
  __ add(R8, R8, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R2 = &digits[a_used >> 1], a_used is Smi.
  __ add(R2, R1, Operand(R2, LSL, 1));
 
  // R6 = &digits[used >> 1], used is Smi.
  __ add(R6, R1, Operand(R0, LSL, 1));
 
  __ subs(R4, R4, Operand(0));  // carry flag = 1
  Label sub_loop;
  __ Bind(&sub_loop);
  // Loop a_used times, a_used > 0.
  __ ldr(R4, Address(R1, kBytesPerBigIntDigit, Address::PostIndex));
  __ ldr(R9, Address(R3, kBytesPerBigIntDigit, Address::PostIndex));
  __ sbcs(R4, R4, Operand(R9));
  __ teq(R1, Operand(R2));  // Does not affect carry flag.
  __ str(R4, Address(R8, kBytesPerBigIntDigit, Address::PostIndex));
  __ b(&sub_loop, NE);
 
  Label done;
  __ teq(R1, Operand(R6));  // Does not affect carry flag.
  __ b(&done, EQ);          // If used - a_used == 0.
 
  Label carry_loop;
  __ Bind(&carry_loop);
  // Loop used - a_used times, used - a_used > 0.
  __ ldr(R4, Address(R1, kBytesPerBigIntDigit, Address::PostIndex));
  __ sbcs(R4, R4, Operand(0));
  __ teq(R1, Operand(R6));  // Does not affect carry flag.
  __ str(R4, Address(R8, kBytesPerBigIntDigit, Address::PostIndex));
  __ b(&carry_loop, NE);
 
  __ Bind(&done);
  __ LoadObject(R0, NullObject());
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_mulAdd(Assembler* assembler,
                                    Label* normal_ir_body) {
  // Pseudo code:
  // static int _mulAdd(Uint32List x_digits, int xi,
  //                    Uint32List m_digits, int i,
  //                    Uint32List a_digits, int j, int n) {
  //   uint32_t x = x_digits[xi >> 1];  // xi is Smi.
  //   if (x == 0 || n == 0) {
  //     return 1;
  //   }
  //   uint32_t* mip = &m_digits[i >> 1];  // i is Smi.
  //   uint32_t* ajp = &a_digits[j >> 1];  // j is Smi.
  //   uint32_t c = 0;
  //   SmiUntag(n);
  //   do {
  //     uint32_t mi = *mip++;
  //     uint32_t aj = *ajp;
  //     uint64_t t = x*mi + aj + c;  // 32-bit * 32-bit -> 64-bit.
  //     *ajp++ = low32(t);
  //     c = high32(t);
  //   } while (--n > 0);
  //   while (c != 0) {
  //     uint64_t t = *ajp + c;
  //     *ajp++ = low32(t);
  //     c = high32(t);  // c == 0 or 1.
  //   }
  //   return 1;
  // }
 
  Label done;
  // R3 = x, no_op if x == 0
  __ ldrd(R0, R1, SP, 5 * target::kWordSize);  // R0 = xi as Smi, R1 = x_digits.
  __ add(R1, R1, Operand(R0, LSL, 1));
  __ ldr(R3, FieldAddress(R1, target::TypedData::payload_offset()));
  __ tst(R3, Operand(R3));
  __ b(&done, EQ);
 
  // R8 = SmiUntag(n), no_op if n == 0
  __ ldr(R8, Address(SP, 0 * target::kWordSize));
  __ Asrs(R8, R8, Operand(kSmiTagSize));
  __ b(&done, EQ);
 
  // R4 = mip = &m_digits[i >> 1]
  __ ldrd(R0, R1, SP, 3 * target::kWordSize);  // R0 = i as Smi, R1 = m_digits.
  __ add(R1, R1, Operand(R0, LSL, 1));
  __ add(R4, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R9 = ajp = &a_digits[j >> 1]
  __ ldrd(R0, R1, SP, 1 * target::kWordSize);  // R0 = j as Smi, R1 = a_digits.
  __ add(R1, R1, Operand(R0, LSL, 1));
  __ add(R9, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R1 = c = 0
  __ mov(R1, Operand(0));
 
  Label muladd_loop;
  __ Bind(&muladd_loop);
  // x:   R3
  // mip: R4
  // ajp: R9
  // c:   R1
  // n:   R8
 
  // uint32_t mi = *mip++
  __ ldr(R2, Address(R4, kBytesPerBigIntDigit, Address::PostIndex));
 
  // uint32_t aj = *ajp
  __ ldr(R0, Address(R9, 0));
 
  // uint64_t t = x*mi + aj + c
  __ umaal(R0, R1, R2, R3);  // R1:R0 = R2*R3 + R1 + R0.
 
  // *ajp++ = low32(t) = R0
  __ str(R0, Address(R9, kBytesPerBigIntDigit, Address::PostIndex));
 
  // c = high32(t) = R1
 
  // while (--n > 0)
  __ subs(R8, R8, Operand(1));  // --n
  __ b(&muladd_loop, NE);
 
  __ tst(R1, Operand(R1));
  __ b(&done, EQ);
 
  // *ajp++ += c
  __ ldr(R0, Address(R9, 0));
  __ adds(R0, R0, Operand(R1));
  __ str(R0, Address(R9, kBytesPerBigIntDigit, Address::PostIndex));
  __ b(&done, CC);
 
  Label propagate_carry_loop;
  __ Bind(&propagate_carry_loop);
  __ ldr(R0, Address(R9, 0));
  __ adds(R0, R0, Operand(1));
  __ str(R0, Address(R9, kBytesPerBigIntDigit, Address::PostIndex));
  __ b(&propagate_carry_loop, CS);
 
  __ Bind(&done);
  __ mov(R0, Operand(target::ToRawSmi(1)));  // One digit processed.
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_sqrAdd(Assembler* assembler,
                                    Label* normal_ir_body) {
  // Pseudo code:
  // static int _sqrAdd(Uint32List x_digits, int i,
  //                    Uint32List a_digits, int used) {
  //   uint32_t* xip = &x_digits[i >> 1];  // i is Smi.
  //   uint32_t x = *xip++;
  //   if (x == 0) return 1;
  //   uint32_t* ajp = &a_digits[i];  // j == 2*i, i is Smi.
  //   uint32_t aj = *ajp;
  //   uint64_t t = x*x + aj;
  //   *ajp++ = low32(t);
  //   uint64_t c = high32(t);
  //   int n = ((used - i) >> 1) - 1;  // used and i are Smi.
  //   while (--n >= 0) {
  //     uint32_t xi = *xip++;
  //     uint32_t aj = *ajp;
  //     uint96_t t = 2*x*xi + aj + c;  // 2-bit * 32-bit * 32-bit -> 65-bit.
  //     *ajp++ = low32(t);
  //     c = high64(t);  // 33-bit.
  //   }
  //   uint32_t aj = *ajp;
  //   uint64_t t = aj + c;  // 32-bit + 33-bit -> 34-bit.
  //   *ajp++ = low32(t);
  //   *ajp = high32(t);
  //   return 1;
  // }
 
  // The code has no bailout path, so we can use R6 (CODE_REG) freely.
 
  // R4 = xip = &x_digits[i >> 1]
  __ ldrd(R2, R3, SP, 2 * target::kWordSize);  // R2 = i as Smi, R3 = x_digits
  __ add(R3, R3, Operand(R2, LSL, 1));
  __ add(R4, R3, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R3 = x = *xip++, return if x == 0
  Label x_zero;
  __ ldr(R3, Address(R4, kBytesPerBigIntDigit, Address::PostIndex));
  __ tst(R3, Operand(R3));
  __ b(&x_zero, EQ);
 
  // R6 = ajp = &a_digits[i]
  __ ldr(R1, Address(SP, 1 * target::kWordSize));  // a_digits
  __ add(R1, R1, Operand(R2, LSL, 2));             // j == 2*i, i is Smi.
  __ add(R6, R1, Operand(target::TypedData::payload_offset() - kHeapObjectTag));
 
  // R8:R0 = t = x*x + *ajp
  __ ldr(R0, Address(R6, 0));
  __ mov(R8, Operand(0));
  __ umaal(R0, R8, R3, R3);  // R8:R0 = R3*R3 + R8 + R0.
 
  // *ajp++ = low32(t) = R0
  __ str(R0, Address(R6, kBytesPerBigIntDigit, Address::PostIndex));
 
  // R8 = low32(c) = high32(t)
  // R9 = high32(c) = 0
  __ mov(R9, Operand(0));
 
  // int n = used - i - 1; while (--n >= 0) ...
  __ ldr(R0, Address(SP, 0 * target::kWordSize));  // used is Smi
  __ sub(TMP, R0, Operand(R2));
  __ mov(R0, Operand(2));  // n = used - i - 2; if (n >= 0) ... while (--n >= 0)
  __ rsbs(TMP, R0, Operand(TMP, ASR, kSmiTagSize));
 
  Label loop, done;
  __ b(&done, MI);
 
  __ Bind(&loop);
  // x:   R3
  // xip: R4
  // ajp: R6
  // c:   R9:R8
  // t:   R2:R1:R0 (not live at loop entry)
  // n:   TMP
 
  // uint32_t xi = *xip++
  __ ldr(R2, Address(R4, kBytesPerBigIntDigit, Address::PostIndex));
 
  // uint96_t t = R9:R8:R0 = 2*x*xi + aj + c
  __ umull(R0, R1, R2, R3);  // R1:R0 = R2*R3.
  __ adds(R0, R0, Operand(R0));
  __ adcs(R1, R1, Operand(R1));
  __ mov(R2, Operand(0));
  __ adc(R2, R2, Operand(0));  // R2:R1:R0 = 2*x*xi.
  __ adds(R0, R0, Operand(R8));
  __ adcs(R1, R1, Operand(R9));
  __ adc(R2, R2, Operand(0));  // R2:R1:R0 = 2*x*xi + c.
  __ ldr(R8, Address(R6, 0));  // R8 = aj = *ajp.
  __ adds(R0, R0, Operand(R8));
  __ adcs(R8, R1, Operand(0));
  __ adc(R9, R2, Operand(0));  // R9:R8:R0 = 2*x*xi + c + aj.
 
  // *ajp++ = low32(t) = R0
  __ str(R0, Address(R6, kBytesPerBigIntDigit, Address::PostIndex));
 
  // while (--n >= 0)
  __ subs(TMP, TMP, Operand(1));  // --n
  __ b(&loop, PL);
 
  __ Bind(&done);
  // uint32_t aj = *ajp
  __ ldr(R0, Address(R6, 0));
 
  // uint64_t t = aj + c
  __ adds(R8, R8, Operand(R0));
  __ adc(R9, R9, Operand(0));
 
  // *ajp = low32(t) = R8
  // *(ajp + 1) = high32(t) = R9
  __ strd(R8, R9, R6, 0);
 
  __ Bind(&x_zero);
  __ mov(R0, Operand(target::ToRawSmi(1)));  // One digit processed.
  __ Ret();
}
 
void AsmIntrinsifier::Bigint_estimateQuotientDigit(Assembler* assembler,
                                                   Label* normal_ir_body) {
  // No unsigned 64-bit / 32-bit divide instruction.
}
 
void AsmIntrinsifier::Montgomery_mulMod(Assembler* assembler,
                                        Label* normal_ir_body) {
  // Pseudo code:
  // static int _mulMod(Uint32List args, Uint32List digits, int i) {
  //   uint32_t rho = args[_RHO];  // _RHO == 2.
  //   uint32_t d = digits[i >> 1];  // i is Smi.
  //   uint64_t t = rho*d;
  //   args[_MU] = t mod DIGIT_BASE;  // _MU == 4.
  //   return 1;
  // }
 
  // R4 = args
  __ ldr(R4, Address(SP, 2 * target::kWordSize));  // args
 
  // R3 = rho = args[2]
  __ ldr(R3, FieldAddress(R4, target::TypedData::payload_offset() +
                                  2 * kBytesPerBigIntDigit));
 
  // R2 = digits[i >> 1]
  __ ldrd(R0, R1, SP, 0 * target::kWordSize);  // R0 = i as Smi, R1 = digits
  __ add(R1, R1, Operand(R0, LSL, 1));
  __ ldr(R2, FieldAddress(R1, target::TypedData::payload_offset()));
 
  // R1:R0 = t = rho*d
  __ umull(R0, R1, R2, R3);
 
  // args[4] = t mod DIGIT_BASE = low32(t)
  __ str(R0, FieldAddress(R4, target::TypedData::payload_offset() +
                                  4 * kBytesPerBigIntDigit));
 
  __ mov(R0, Operand(target::ToRawSmi(1)));  // One digit 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 R0.
static void TestLastArgumentIsDouble(Assembler* assembler,
                                     Label* is_smi,
                                     Label* not_double_smi) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ tst(R0, Operand(kSmiTagMask));
  __ b(is_smi, EQ);
  __ CompareClassId(R0, kDoubleCid, R1);
  __ b(not_double_smi, NE);
  // Fall through with Double in R0.
}
 
// Both arguments on stack, arg0 (left) is a double, arg1 (right) is of unknown
// type. Return true or false object in the register R0. Any NaN argument
// returns false. Any non-double arg1 causes control flow to fall through to the
// slow case (compiled method body).
static void CompareDoubles(Assembler* assembler,
                           Label* normal_ir_body,
                           Condition true_condition) {
  Label is_smi, double_op;
 
  TestLastArgumentIsDouble(assembler, &is_smi, normal_ir_body);
  // Both arguments are double, right operand is in R0.
 
  __ LoadDFromOffset(D1, R0, target::Double::value_offset() - kHeapObjectTag);
  __ Bind(&double_op);
  __ ldr(R0, Address(SP, 1 * target::kWordSize));  // Left argument.
  __ LoadDFromOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
 
  __ vcmpd(D0, D1);
  __ vmstat();
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  // Return false if D0 or D1 was NaN before checking true condition.
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, VS));
  __ LoadObject(R0, CastHandle<Object>(TrueObject()), true_condition);
  __ Ret();
 
  __ Bind(&is_smi);  // Convert R0 to a double.
  __ SmiUntag(R0);
  __ vmovsr(S0, R0);
  __ vcvtdi(D1, S0);
  __ b(&double_op);  // Then do the comparison.
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::Double_greaterThan(Assembler* assembler,
                                         Label* normal_ir_body) {
  CompareDoubles(assembler, normal_ir_body, HI);
}
 
void AsmIntrinsifier::Double_greaterEqualThan(Assembler* assembler,
                                              Label* normal_ir_body) {
  CompareDoubles(assembler, normal_ir_body, CS);
}
 
void AsmIntrinsifier::Double_lessThan(Assembler* assembler,
                                      Label* normal_ir_body) {
  CompareDoubles(assembler, normal_ir_body, CC);
}
 
void AsmIntrinsifier::Double_equal(Assembler* assembler,
                                   Label* normal_ir_body) {
  CompareDoubles(assembler, normal_ir_body, EQ);
}
 
void AsmIntrinsifier::Double_lessEqualThan(Assembler* assembler,
                                           Label* normal_ir_body) {
  CompareDoubles(assembler, normal_ir_body, LS);
}
 
// Expects left argument to be double (receiver). Right argument is unknown.
// Both arguments are on stack.
static void DoubleArithmeticOperations(Assembler* assembler,
                                       Label* normal_ir_body,
                                       Token::Kind kind) {
  Label is_smi, double_op;
 
  TestLastArgumentIsDouble(assembler, &is_smi, normal_ir_body);
  // Both arguments are double, right operand is in R0.
  __ LoadDFromOffset(D1, R0, target::Double::value_offset() - kHeapObjectTag);
  __ Bind(&double_op);
  __ ldr(R0, Address(SP, 1 * target::kWordSize));  // Left argument.
  __ LoadDFromOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  switch (kind) {
    case Token::kADD:
      __ vaddd(D0, D0, D1);
      break;
    case Token::kSUB:
      __ vsubd(D0, D0, D1);
      break;
    case Token::kMUL:
      __ vmuld(D0, D0, D1);
      break;
    case Token::kDIV:
      __ vdivd(D0, D0, D1);
      break;
    default:
      UNREACHABLE();
  }
  const Class& double_class = DoubleClass();
  __ TryAllocate(double_class, normal_ir_body, Assembler::kFarJump, R0,
                 R1);  // Result register.
  __ StoreDToOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  __ Ret();
  __ Bind(&is_smi);  // Convert R0 to a double.
  __ SmiUntag(R0);
  __ vmovsr(S0, R0);
  __ vcvtdi(D1, S0);
  __ b(&double_op);
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::Double_add(Assembler* assembler, Label* normal_ir_body) {
  DoubleArithmeticOperations(assembler, normal_ir_body, Token::kADD);
}
 
void AsmIntrinsifier::Double_mul(Assembler* assembler, Label* normal_ir_body) {
  DoubleArithmeticOperations(assembler, normal_ir_body, Token::kMUL);
}
 
void AsmIntrinsifier::Double_sub(Assembler* assembler, Label* normal_ir_body) {
  DoubleArithmeticOperations(assembler, normal_ir_body, Token::kSUB);
}
 
void AsmIntrinsifier::Double_div(Assembler* assembler, Label* normal_ir_body) {
  DoubleArithmeticOperations(assembler, normal_ir_body, Token::kDIV);
}
 
// Left is double, right is integer (Mint or Smi)
void AsmIntrinsifier::Double_mulFromInteger(Assembler* assembler,
                                            Label* normal_ir_body) {
  Label fall_through;
  // Only smis allowed.
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ tst(R0, Operand(kSmiTagMask));
  __ b(normal_ir_body, NE);
  // Is Smi.
  __ SmiUntag(R0);
  __ vmovsr(S0, R0);
  __ vcvtdi(D1, S0);
  __ ldr(R0, Address(SP, 1 * target::kWordSize));
  __ LoadDFromOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  __ vmuld(D0, D0, D1);
  const Class& double_class = DoubleClass();
  __ TryAllocate(double_class, normal_ir_body, Assembler::kFarJump, R0,
                 R1);  // Result register.
  __ StoreDToOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  __ Ret();
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::DoubleFromInteger(Assembler* assembler,
                                        Label* normal_ir_body) {
  Label fall_through;
 
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ tst(R0, Operand(kSmiTagMask));
  __ b(normal_ir_body, NE);
  // Is Smi.
  __ SmiUntag(R0);
  __ vmovsr(S0, R0);
  __ vcvtdi(D0, S0);
  const Class& double_class = DoubleClass();
  __ TryAllocate(double_class, normal_ir_body, Assembler::kFarJump, R0,
                 R1);  // Result register.
  __ StoreDToOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  __ Ret();
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::Double_getIsNaN(Assembler* assembler,
                                      Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ LoadDFromOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  __ vcmpd(D0, D0);
  __ vmstat();
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), VC);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()), VS);
  __ Ret();
}
 
void AsmIntrinsifier::Double_getIsInfinite(Assembler* assembler,
                                           Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  // R1 <- value[0:31], R2 <- value[32:63]
  __ LoadFieldFromOffset(R1, R0, target::Double::value_offset());
  __ LoadFieldFromOffset(R2, R0,
                         target::Double::value_offset() + target::kWordSize);
 
  // If the low word isn't 0, then it isn't infinity.
  __ cmp(R1, Operand(0));
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), NE);
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, NE));  // Return if NE.
 
  // Mask off the sign bit.
  __ AndImmediate(R2, R2, 0x7FFFFFFF);
  // Compare with +infinity.
  __ CompareImmediate(R2, 0x7FF00000);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), NE);
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, NE));
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
}
 
void AsmIntrinsifier::Double_getIsNegative(Assembler* assembler,
                                           Label* normal_ir_body) {
  Label is_false, is_true, is_zero;
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ LoadDFromOffset(D0, R0, target::Double::value_offset() - kHeapObjectTag);
  __ vcmpdz(D0);
  __ vmstat();
  __ b(&is_false, VS);  // NaN -> false.
  __ b(&is_zero, EQ);   // Check for negative zero.
  __ b(&is_false, CS);  // >= 0 -> false.
 
  __ Bind(&is_true);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  __ Bind(&is_false);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
 
  __ Bind(&is_zero);
  // Check for negative zero by looking at the sign bit.
  __ vmovrrd(R0, R1, D0);  // R1:R0 <- D0, so sign bit is in bit 31 of R1.
  __ mov(R1, Operand(R1, LSR, 31));
  __ tst(R1, Operand(1));
  __ b(&is_true, NE);  // Sign bit set.
  __ b(&is_false);
}
 
void AsmIntrinsifier::ObjectEquals(Assembler* assembler,
                                   Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ ldr(R1, Address(SP, 1 * target::kWordSize));
  __ cmp(R0, Operand(R1));
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), NE);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()), EQ);
  __ Ret();
}
 
static void JumpIfInteger(Assembler* assembler,
                          Register cid,
                          Register tmp,
                          Label* target) {
  assembler->RangeCheck(cid, tmp, kSmiCid, kMintCid, Assembler::kIfInRange,
                        target);
}
 
static void JumpIfNotInteger(Assembler* assembler,
                             Register cid,
                             Register tmp,
                             Label* target) {
  assembler->RangeCheck(cid, tmp, kSmiCid, kMintCid, Assembler::kIfNotInRange,
                        target);
}
 
static void JumpIfString(Assembler* assembler,
                         Register cid,
                         Register tmp,
                         Label* target) {
  assembler->RangeCheck(cid, tmp, kOneByteStringCid, kTwoByteStringCid,
                        Assembler::kIfInRange, target);
}
 
static void JumpIfNotString(Assembler* assembler,
                            Register cid,
                            Register tmp,
                            Label* target) {
  assembler->RangeCheck(cid, tmp, kOneByteStringCid, kTwoByteStringCid,
                        Assembler::kIfNotInRange, target);
}
 
static void JumpIfNotList(Assembler* assembler,
                          Register cid,
                          Register tmp,
                          Label* target) {
  assembler->RangeCheck(cid, tmp, kArrayCid, kGrowableObjectArrayCid,
                        Assembler::kIfNotInRange, target);
}
 
static void JumpIfType(Assembler* assembler,
                       Register cid,
                       Register tmp,
                       Label* target) {
  COMPILE_ASSERT((kFunctionTypeCid == kTypeCid + 1) &&
                 (kRecordTypeCid == kTypeCid + 2));
  assembler->RangeCheck(cid, tmp, kTypeCid, kRecordTypeCid,
                        Assembler::kIfInRange, target);
}
 
static void JumpIfNotType(Assembler* assembler,
                          Register cid,
                          Register tmp,
                          Label* target) {
  COMPILE_ASSERT((kFunctionTypeCid == kTypeCid + 1) &&
                 (kRecordTypeCid == kTypeCid + 2));
  assembler->RangeCheck(cid, tmp, kTypeCid, kRecordTypeCid,
                        Assembler::kIfNotInRange, target);
}
 
// Return type quickly for simple types (not parameterized and not signature).
void AsmIntrinsifier::ObjectRuntimeType(Assembler* assembler,
                                        Label* normal_ir_body) {
  Label use_declaration_type, not_double, not_integer, not_string;
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ LoadClassIdMayBeSmi(R1, R0);
 
  __ CompareImmediate(R1, kClosureCid);
  __ b(normal_ir_body, EQ);  // Instance is a closure.
 
  __ CompareImmediate(R1, kRecordCid);
  __ b(normal_ir_body, EQ);  // Instance is a record.
 
  __ CompareImmediate(R1, kNumPredefinedCids);
  __ b(&use_declaration_type, HI);
 
  __ LoadIsolateGroup(R2);
  __ LoadFromOffset(R2, R2, target::IsolateGroup::object_store_offset());
 
  __ CompareImmediate(R1, kDoubleCid);
  __ b(&not_double, NE);
  __ LoadFromOffset(R0, R2, target::ObjectStore::double_type_offset());
  __ Ret();
 
  __ Bind(&not_double);
  JumpIfNotInteger(assembler, R1, R0, &not_integer);
  __ LoadFromOffset(R0, R2, target::ObjectStore::int_type_offset());
  __ Ret();
 
  __ Bind(&not_integer);
  JumpIfNotString(assembler, R1, R0, &not_string);
  __ LoadFromOffset(R0, R2, target::ObjectStore::string_type_offset());
  __ Ret();
 
  __ Bind(&not_string);
  JumpIfNotType(assembler, R1, R0, &use_declaration_type);
  __ LoadFromOffset(R0, R2, target::ObjectStore::type_type_offset());
  __ Ret();
 
  __ Bind(&use_declaration_type);
  __ LoadClassById(R2, R1);
  __ ldrh(R3, FieldAddress(R2, target::Class::num_type_arguments_offset()));
  __ CompareImmediate(R3, 0);
  __ b(normal_ir_body, NE);
 
  __ ldr(R0, FieldAddress(R2, target::Class::declaration_type_offset()));
  __ CompareObject(R0, NullObject());
  __ b(normal_ir_body, EQ);
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
// Compares cid1 and cid2 to see if they're syntactically equivalent. If this
// can be determined by this fast path, it jumps to either equal_* or not_equal.
// If classes are equivalent but may be generic, then jumps to
// equal_may_be_generic. Clobbers scratch.
static void EquivalentClassIds(Assembler* assembler,
                               Label* normal_ir_body,
                               Label* equal_may_be_generic,
                               Label* equal_not_generic,
                               Label* not_equal,
                               Register cid1,
                               Register cid2,
                               Register scratch,
                               bool testing_instance_cids) {
  Label not_integer, not_integer_or_string, not_integer_or_string_or_list;
 
  // Check if left hand side is a closure. Closures are handled in the runtime.
  __ CompareImmediate(cid1, kClosureCid);
  __ b(normal_ir_body, EQ);
 
  // Check if left hand side is a record. Records are handled in the runtime.
  __ CompareImmediate(cid1, kRecordCid);
  __ b(normal_ir_body, EQ);
 
  // Check whether class ids match. If class ids don't match types may still be
  // considered equivalent (e.g. multiple string implementation classes map to a
  // single String type).
  __ cmp(cid1, Operand(cid2));
  __ b(equal_may_be_generic, EQ);
 
  // Class ids are different. Check if we are comparing two string types (with
  // different representations), two integer types, two list types or two type
  // types.
  __ CompareImmediate(cid1, kNumPredefinedCids);
  __ b(not_equal, HI);
 
  // Check if both are integer types.
  JumpIfNotInteger(assembler, cid1, scratch, &not_integer);
 
  // First type is an integer. Check if the second is an integer too.
  JumpIfInteger(assembler, cid2, scratch, equal_not_generic);
  // Integer types are only equivalent to other integer types.
  __ b(not_equal);
 
  __ Bind(&not_integer);
  // Check if both are String types.
  JumpIfNotString(assembler, cid1, scratch,
                  testing_instance_cids ? &not_integer_or_string : not_equal);
 
  // First type is String. Check if the second is a string too.
  JumpIfString(assembler, cid2, scratch, equal_not_generic);
  // String types are only equivalent to other String types.
  __ b(not_equal);
 
  if (testing_instance_cids) {
    __ Bind(&not_integer_or_string);
    // Check if both are List types.
    JumpIfNotList(assembler, cid1, scratch, &not_integer_or_string_or_list);
 
    // First type is a List. Check if the second is a List too.
    JumpIfNotList(assembler, cid2, scratch, not_equal);
    ASSERT(compiler::target::Array::type_arguments_offset() ==
           compiler::target::GrowableObjectArray::type_arguments_offset());
    __ b(equal_may_be_generic);
 
    __ Bind(&not_integer_or_string_or_list);
    // Check if the first type is a Type. If it is not then types are not
    // equivalent because they have different class ids and they are not String
    // or integer or List or Type.
    JumpIfNotType(assembler, cid1, scratch, not_equal);
 
    // First type is a Type. Check if the second is a Type too.
    JumpIfType(assembler, cid2, scratch, equal_not_generic);
    // Type types are only equivalent to other Type types.
    __ b(not_equal);
  }
}
 
void AsmIntrinsifier::ObjectHaveSameRuntimeType(Assembler* assembler,
                                                Label* normal_ir_body) {
  __ ldm(IA, SP, (1 << R1 | 1 << R2));
  __ LoadClassIdMayBeSmi(R1, R1);
  __ LoadClassIdMayBeSmi(R2, R2);
 
  Label equal_may_be_generic, equal, not_equal;
  EquivalentClassIds(assembler, normal_ir_body, &equal_may_be_generic, &equal,
                     &not_equal, R1, R2, R0,
                     /* testing_instance_cids = */ true);
 
  __ Bind(&equal_may_be_generic);
  // Classes are equivalent and neither is a closure class.
  // Check if there are no type arguments. In this case we can return true.
  // Otherwise fall through into the runtime to handle comparison.
  __ LoadClassById(R0, R1);
  __ ldr(
      R0,
      FieldAddress(
          R0,
          target::Class::host_type_arguments_field_offset_in_words_offset()));
  __ CompareImmediate(R0, target::Class::kNoTypeArguments);
  __ b(&equal, EQ);
 
  // Compare type arguments, host_type_arguments_field_offset_in_words in R0.
  __ ldm(IA, SP, (1 << R1 | 1 << R2));
  __ AddImmediate(R1, -kHeapObjectTag);
  __ ldr(R1, Address(R1, R0, LSL, target::kWordSizeLog2));
  __ AddImmediate(R2, -kHeapObjectTag);
  __ ldr(R2, Address(R2, R0, LSL, target::kWordSizeLog2));
  __ cmp(R1, Operand(R2));
  __ b(normal_ir_body, NE);
  // Fall through to equal case if type arguments are equal.
 
  __ Bind(&equal);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  __ Bind(&not_equal);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::String_getHashCode(Assembler* assembler,
                                         Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ ldr(R0, FieldAddress(R0, target::String::hash_offset()));
  __ cmp(R0, Operand(0));
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, NE));
  __ Bind(normal_ir_body);  // Hash not yet computed.
}
 
void AsmIntrinsifier::Type_equality(Assembler* assembler,
                                    Label* normal_ir_body) {
  Label equal, not_equal, equiv_cids_may_be_generic, equiv_cids;
 
  __ ldm(IA, SP, (1 << R1 | 1 << R2));
  __ cmp(R1, Operand(R2));
  __ b(&equal, EQ);
 
  // R1 might not be a Type object, so check that first (R2 should be though,
  // since this is a method on the Type class).
  __ LoadClassIdMayBeSmi(R0, R1);
  __ CompareImmediate(R0, kTypeCid);
  __ b(normal_ir_body, NE);
 
  // Check if types are syntactically equal.
  __ LoadTypeClassId(R3, R1);
  __ LoadTypeClassId(R4, R2);
  // We are not testing instance cids, but type class cids of Type instances.
  EquivalentClassIds(assembler, normal_ir_body, &equiv_cids_may_be_generic,
                     &equiv_cids, &not_equal, R3, R4, R0,
                     /* testing_instance_cids = */ false);
 
  __ Bind(&equiv_cids_may_be_generic);
  // Compare type arguments in Type instances.
  __ ldr(R3, FieldAddress(R1, target::Type::arguments_offset()));
  __ ldr(R4, FieldAddress(R2, target::Type::arguments_offset()));
  __ cmp(R3, Operand(R4));
  __ b(normal_ir_body, NE);
  // Fall through to check nullability if type arguments are equal.
 
  // Check nullability.
  __ Bind(&equiv_cids);
  __ LoadAbstractTypeNullability(R1, R1);
  __ LoadAbstractTypeNullability(R2, R2);
  __ cmp(R1, Operand(R2));
  __ b(&not_equal, NE);
  // Fall through to equal case if nullability is equal.
 
  __ Bind(&equal);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  __ Bind(&not_equal);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::AbstractType_getHashCode(Assembler* assembler,
                                               Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ ldr(R0, FieldAddress(R0, target::AbstractType::hash_offset()));
  __ cmp(R0, Operand(0));
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, NE));
  __ Bind(normal_ir_body);  // Hash not yet computed.
}
 
void AsmIntrinsifier::AbstractType_equality(Assembler* assembler,
                                            Label* normal_ir_body) {
  __ ldm(IA, SP, (1 << R1 | 1 << R2));
  __ cmp(R1, Operand(R2));
  __ b(normal_ir_body, NE);
 
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
void GenerateSubstringMatchesSpecialization(Assembler* assembler,
                                            intptr_t receiver_cid,
                                            intptr_t other_cid,
                                            Label* return_true,
                                            Label* return_false) {
  __ SmiUntag(R1);
  __ ldr(R8, FieldAddress(R0, target::String::length_offset()));  // this.length
  __ SmiUntag(R8);
  __ ldr(R9,
         FieldAddress(R2, target::String::length_offset()));  // other.length
  __ SmiUntag(R9);
 
  // if (other.length == 0) return true;
  __ cmp(R9, Operand(0));
  __ b(return_true, EQ);
 
  // if (start < 0) return false;
  __ cmp(R1, Operand(0));
  __ b(return_false, LT);
 
  // if (start + other.length > this.length) return false;
  __ add(R3, R1, Operand(R9));
  __ cmp(R3, Operand(R8));
  __ b(return_false, GT);
 
  if (receiver_cid == kOneByteStringCid) {
    __ AddImmediate(R0, target::OneByteString::data_offset() - kHeapObjectTag);
    __ add(R0, R0, Operand(R1));
  } else {
    ASSERT(receiver_cid == kTwoByteStringCid);
    __ AddImmediate(R0, target::TwoByteString::data_offset() - kHeapObjectTag);
    __ add(R0, R0, Operand(R1));
    __ add(R0, R0, Operand(R1));
  }
  if (other_cid == kOneByteStringCid) {
    __ AddImmediate(R2, target::OneByteString::data_offset() - kHeapObjectTag);
  } else {
    ASSERT(other_cid == kTwoByteStringCid);
    __ AddImmediate(R2, target::TwoByteString::data_offset() - kHeapObjectTag);
  }
 
  // i = 0
  __ LoadImmediate(R3, 0);
 
  // do
  Label loop;
  __ Bind(&loop);
 
  if (receiver_cid == kOneByteStringCid) {
    __ ldrb(R4, Address(R0, 0));  // this.codeUnitAt(i + start)
  } else {
    __ ldrh(R4, Address(R0, 0));  // this.codeUnitAt(i + start)
  }
  if (other_cid == kOneByteStringCid) {
    __ ldrb(TMP, Address(R2, 0));  // other.codeUnitAt(i)
  } else {
    __ ldrh(TMP, Address(R2, 0));  // other.codeUnitAt(i)
  }
  __ cmp(R4, Operand(TMP));
  __ b(return_false, NE);
 
  // i++, while (i < len)
  __ AddImmediate(R3, 1);
  __ AddImmediate(R0, receiver_cid == kOneByteStringCid ? 1 : 2);
  __ AddImmediate(R2, other_cid == kOneByteStringCid ? 1 : 2);
  __ cmp(R3, Operand(R9));
  __ b(&loop, LT);
 
  __ b(return_true);
}
 
// bool _substringMatches(int start, String other)
// This intrinsic handles a OneByteString or TwoByteString receiver with a
// OneByteString other.
void AsmIntrinsifier::StringBaseSubstringMatches(Assembler* assembler,
                                                 Label* normal_ir_body) {
  Label return_true, return_false, try_two_byte;
  __ ldr(R0, Address(SP, 2 * target::kWordSize));  // this
  __ ldr(R1, Address(SP, 1 * target::kWordSize));  // start
  __ ldr(R2, Address(SP, 0 * target::kWordSize));  // other
  __ Push(R4);  // Make ARGS_DESC_REG available.
 
  __ tst(R1, Operand(kSmiTagMask));
  __ b(normal_ir_body, NE);  // 'start' is not a Smi.
 
  __ CompareClassId(R2, kOneByteStringCid, R3);
  __ b(normal_ir_body, NE);
 
  __ CompareClassId(R0, kOneByteStringCid, R3);
  __ b(&try_two_byte, NE);
 
  GenerateSubstringMatchesSpecialization(assembler, kOneByteStringCid,
                                         kOneByteStringCid, &return_true,
                                         &return_false);
 
  __ Bind(&try_two_byte);
  __ CompareClassId(R0, kTwoByteStringCid, R3);
  __ b(normal_ir_body, NE);
 
  GenerateSubstringMatchesSpecialization(assembler, kTwoByteStringCid,
                                         kOneByteStringCid, &return_true,
                                         &return_false);
 
  __ Bind(&return_true);
  __ Pop(R4);
  __ LoadObject(R0, CastHandle<Object>(TrueObject()));
  __ Ret();
 
  __ Bind(&return_false);
  __ Pop(R4);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
 
  __ Bind(normal_ir_body);
  __ Pop(R4);
}
 
void AsmIntrinsifier::Object_getHash(Assembler* assembler,
                                     Label* normal_ir_body) {
  UNREACHABLE();
}
 
void AsmIntrinsifier::StringBaseCharAt(Assembler* assembler,
                                       Label* normal_ir_body) {
  Label try_two_byte_string;
 
  __ ldr(R1, Address(SP, 0 * target::kWordSize));  // Index.
  __ ldr(R0, Address(SP, 1 * target::kWordSize));  // String.
  __ tst(R1, Operand(kSmiTagMask));
  __ b(normal_ir_body, NE);  // Index is not a Smi.
  // Range check.
  __ ldr(R2, FieldAddress(R0, target::String::length_offset()));
  __ cmp(R1, Operand(R2));
  __ b(normal_ir_body, CS);  // Runtime throws exception.
 
  __ CompareClassId(R0, kOneByteStringCid, R3);
  __ b(&try_two_byte_string, NE);
  __ SmiUntag(R1);
  __ AddImmediate(R0, target::OneByteString::data_offset() - kHeapObjectTag);
  __ ldrb(R1, Address(R0, R1));
  __ CompareImmediate(R1, target::Symbols::kNumberOfOneCharCodeSymbols);
  __ b(normal_ir_body, GE);
  __ ldr(R0, Address(THR, target::Thread::predefined_symbols_address_offset()));
  __ AddImmediate(
      R0, target::Symbols::kNullCharCodeSymbolOffset * target::kWordSize);
  __ ldr(R0, Address(R0, R1, LSL, 2));
  __ Ret();
 
  __ Bind(&try_two_byte_string);
  __ CompareClassId(R0, kTwoByteStringCid, R3);
  __ b(normal_ir_body, NE);
  ASSERT(kSmiTagShift == 1);
  __ AddImmediate(R0, target::TwoByteString::data_offset() - kHeapObjectTag);
  __ ldrh(R1, Address(R0, R1));
  __ CompareImmediate(R1, target::Symbols::kNumberOfOneCharCodeSymbols);
  __ b(normal_ir_body, GE);
  __ ldr(R0, Address(THR, target::Thread::predefined_symbols_address_offset()));
  __ AddImmediate(
      R0, target::Symbols::kNullCharCodeSymbolOffset * target::kWordSize);
  __ ldr(R0, Address(R0, R1, LSL, 2));
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::StringBaseIsEmpty(Assembler* assembler,
                                        Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 0 * target::kWordSize));
  __ ldr(R0, FieldAddress(R0, target::String::length_offset()));
  __ cmp(R0, Operand(target::ToRawSmi(0)));
  __ LoadObject(R0, CastHandle<Object>(TrueObject()), EQ);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), NE);
  __ Ret();
}
 
void AsmIntrinsifier::OneByteString_getHashCode(Assembler* assembler,
                                                Label* normal_ir_body) {
  __ ldr(R1, Address(SP, 0 * target::kWordSize));
  __ ldr(R0, FieldAddress(R1, target::String::hash_offset()));
  __ cmp(R0, Operand(0));
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR, NE));  // Return if already computed.
  __ ldr(R2, FieldAddress(R1, target::String::length_offset()));
  __ SmiUntag(R2);
  __ mov(R3, Operand(0));
  __ AddImmediate(R8, R1,
                  target::OneByteString::data_offset() - kHeapObjectTag);
 
  // R1: Instance of OneByteString.
  // R2: String length, untagged integer.
  // R3: Loop counter, untagged integer.
  // R8: String data.
  // R0: Hash code, untagged integer.
 
  Label loop, done;
  __ Bind(&loop);
  __ cmp(R3, Operand(R2));
  __ b(&done, EQ);
  // Add to hash code: (hash_ is uint32)
  // Get one characters (ch).
  __ ldrb(TMP, Address(R8, 0));
  // TMP: ch.
  __ add(R3, R3, Operand(1));
  __ add(R8, R8, Operand(1));
  __ CombineHashes(R0, TMP);
  __ b(&loop);
 
  __ Bind(&done);
  // Finalize. Allow a zero result to combine checks from empty string branch.
  __ FinalizeHashForSize(target::String::kHashBits, R0);
  __ SmiTag(R0);
  __ StoreIntoSmiField(FieldAddress(R1, target::String::hash_offset()), R0);
  __ Ret();
}
 
// Allocates a _OneByteString or _TwoByteString. The content is not initialized.
// 'length-reg' (R2) contains the desired length as a _Smi or _Mint.
// Returns new string as tagged pointer in R0.
static void TryAllocateString(Assembler* assembler,
                              classid_t cid,
                              intptr_t max_elements,
                              Label* ok,
                              Label* failure) {
  ASSERT(cid == kOneByteStringCid || cid == kTwoByteStringCid);
  const Register length_reg = R2;
  // _Mint length: call to runtime to produce error.
  __ BranchIfNotSmi(length_reg, failure);
  // Negative length: call to runtime to produce error.
  // Too big: call to runtime to allocate old.
  __ CompareImmediate(length_reg, target::ToRawSmi(max_elements));
  __ b(failure, HI);
 
  NOT_IN_PRODUCT(__ MaybeTraceAllocation(cid, failure, R0));
  __ mov(R8, Operand(length_reg));  // Save the length register.
  if (cid == kOneByteStringCid) {
    __ SmiUntag(length_reg);
  } else {
    // Untag length and multiply by element size -> no-op.
  }
  const intptr_t fixed_size_plus_alignment_padding =
      target::String::InstanceSize() +
      target::ObjectAlignment::kObjectAlignment - 1;
  __ AddImmediate(length_reg, fixed_size_plus_alignment_padding);
  __ bic(length_reg, length_reg,
         Operand(target::ObjectAlignment::kObjectAlignment - 1));
 
  __ ldr(R0, Address(THR, target::Thread::top_offset()));
 
  // length_reg: allocation size.
  __ adds(R1, R0, Operand(length_reg));
  __ b(failure, CS);  // Fail on unsigned overflow.
 
  // Check if the allocation fits into the remaining space.
  // R0: potential new object start.
  // R1: potential next object start.
  // R2: allocation size.
  __ ldr(TMP, Address(THR, target::Thread::end_offset()));
  __ cmp(R1, Operand(TMP));
  __ b(failure, CS);
  __ CheckAllocationCanary(R0);
 
  // Successfully allocated the object(s), now update top to point to
  // next object start and initialize the object.
  __ str(R1, Address(THR, target::Thread::top_offset()));
  __ AddImmediate(R0, kHeapObjectTag);
  // Clear last double word to ensure string comparison doesn't need to
  // specially handle remainder of strings with lengths not factors of double
  // offsets.
  __ LoadImmediate(TMP, 0);
  __ str(TMP, Address(R1, -1 * target::kWordSize));
  __ str(TMP, Address(R1, -2 * target::kWordSize));
 
  // Initialize the tags.
  // R0: new object start as a tagged pointer.
  // R1: new object end address.
  // R2: allocation size.
  {
    const intptr_t shift = target::UntaggedObject::kTagBitsSizeTagPos -
                           target::ObjectAlignment::kObjectAlignmentLog2;
 
    __ CompareImmediate(R2, target::UntaggedObject::kSizeTagMaxSizeTag);
    __ mov(R3, Operand(R2, LSL, shift), LS);
    __ mov(R3, Operand(0), HI);
 
    // Get the class index and insert it into the tags.
    // R3: size and bit tags.
    const uword tags =
        target::MakeTagWordForNewSpaceObject(cid, /*instance_size=*/0);
    __ LoadImmediate(TMP, tags);
    __ orr(R3, R3, Operand(TMP));
    __ str(R3, FieldAddress(R0, target::Object::tags_offset()));  // Store tags.
  }
 
  // Set the length field using the saved length (R8).
  __ StoreIntoObjectNoBarrier(
      R0, FieldAddress(R0, target::String::length_offset()), R8);
  // Clear hash.
  __ LoadImmediate(TMP, 0);
  __ StoreIntoObjectNoBarrier(
      R0, FieldAddress(R0, target::String::hash_offset()), TMP);
 
  __ b(ok);
}
 
// Arg0: OneByteString (receiver).
// Arg1: Start index as Smi.
// Arg2: End index as Smi.
// The indexes must be valid.
void AsmIntrinsifier::OneByteString_substringUnchecked(Assembler* assembler,
                                                       Label* normal_ir_body) {
  const intptr_t kStringOffset = 2 * target::kWordSize;
  const intptr_t kStartIndexOffset = 1 * target::kWordSize;
  const intptr_t kEndIndexOffset = 0 * target::kWordSize;
  Label ok;
 
  __ ldr(R2, Address(SP, kEndIndexOffset));
  __ ldr(TMP, Address(SP, kStartIndexOffset));
  __ orr(R3, R2, Operand(TMP));
  __ tst(R3, Operand(kSmiTagMask));
  __ b(normal_ir_body, NE);  // 'start', 'end' not Smi.
 
  __ sub(R2, R2, Operand(TMP));
  TryAllocateString(assembler, kOneByteStringCid,
                    target::OneByteString::kMaxNewSpaceElements, &ok,
                    normal_ir_body);
  __ Bind(&ok);
  // R0: new string as tagged pointer.
  // Copy string.
  __ ldr(R3, Address(SP, kStringOffset));
  __ ldr(R1, Address(SP, kStartIndexOffset));
  __ SmiUntag(R1);
  __ add(R3, R3, Operand(R1));
  // Calculate start address and untag (- 1).
  __ AddImmediate(R3, target::OneByteString::data_offset() - 1);
 
  // R3: Start address to copy from (untagged).
  // R1: Untagged start index.
  __ ldr(R2, Address(SP, kEndIndexOffset));
  __ SmiUntag(R2);
  __ sub(R2, R2, Operand(R1));
 
  // R3: Start address to copy from (untagged).
  // R2: Untagged number of bytes to copy.
  // R0: Tagged result string.
  // R8: Pointer into R3.
  // R1: Pointer into R0.
  // TMP: Scratch register.
  Label loop, done;
  __ cmp(R2, Operand(0));
  __ b(&done, LE);
  __ mov(R8, Operand(R3));
  __ mov(R1, Operand(R0));
  __ Bind(&loop);
  __ ldrb(TMP, Address(R8, 1, Address::PostIndex));
  __ sub(R2, R2, Operand(1));
  __ cmp(R2, Operand(0));
  __ strb(TMP, FieldAddress(R1, target::OneByteString::data_offset()));
  __ add(R1, R1, Operand(1));
  __ b(&loop, GT);
 
  __ Bind(&done);
  __ Ret();
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::WriteIntoOneByteString(Assembler* assembler,
                                             Label* normal_ir_body) {
  __ ldr(R2, Address(SP, 0 * target::kWordSize));  // Value.
  __ ldr(R1, Address(SP, 1 * target::kWordSize));  // Index.
  __ ldr(R0, Address(SP, 2 * target::kWordSize));  // OneByteString.
  __ SmiUntag(R1);
  __ SmiUntag(R2);
  __ AddImmediate(R3, R0,
                  target::OneByteString::data_offset() - kHeapObjectTag);
  __ strb(R2, Address(R3, R1));
  __ Ret();
}
 
void AsmIntrinsifier::WriteIntoTwoByteString(Assembler* assembler,
                                             Label* normal_ir_body) {
  __ ldr(R2, Address(SP, 0 * target::kWordSize));  // Value.
  __ ldr(R1, Address(SP, 1 * target::kWordSize));  // Index.
  __ ldr(R0, Address(SP, 2 * target::kWordSize));  // TwoByteString.
  // Untag index and multiply by element size -> no-op.
  __ SmiUntag(R2);
  __ AddImmediate(R3, R0,
                  target::TwoByteString::data_offset() - kHeapObjectTag);
  __ strh(R2, Address(R3, R1));
  __ Ret();
}
 
void AsmIntrinsifier::AllocateOneByteString(Assembler* assembler,
                                            Label* normal_ir_body) {
  __ ldr(R2, Address(SP, 0 * target::kWordSize));  // Length.
  Label ok;
  TryAllocateString(assembler, kOneByteStringCid,
                    target::OneByteString::kMaxNewSpaceElements, &ok,
                    normal_ir_body);
 
  __ Bind(&ok);
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::AllocateTwoByteString(Assembler* assembler,
                                            Label* normal_ir_body) {
  __ ldr(R2, Address(SP, 0 * target::kWordSize));  // Length.
  Label ok;
  TryAllocateString(assembler, kTwoByteStringCid,
                    target::TwoByteString::kMaxNewSpaceElements, &ok,
                    normal_ir_body);
 
  __ Bind(&ok);
  __ Ret();
 
  __ Bind(normal_ir_body);
}
 
void AsmIntrinsifier::OneByteString_equality(Assembler* assembler,
                                             Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 1 * target::kWordSize));  // This.
  __ ldr(R1, Address(SP, 0 * target::kWordSize));  // Other.
 
  StringEquality(assembler, R0, R1, R2, R3, R0, normal_ir_body,
                 kOneByteStringCid);
}
 
void AsmIntrinsifier::TwoByteString_equality(Assembler* assembler,
                                             Label* normal_ir_body) {
  __ ldr(R0, Address(SP, 1 * target::kWordSize));  // This.
  __ ldr(R1, Address(SP, 0 * target::kWordSize));  // Other.
 
  StringEquality(assembler, R0, R1, R2, R3, R0, normal_ir_body,
                 kTwoByteStringCid);
}
 
void AsmIntrinsifier::IntrinsifyRegExpExecuteMatch(Assembler* assembler,
                                                   Label* normal_ir_body,
                                                   bool sticky) {
  if (FLAG_interpret_irregexp) return;
 
  const intptr_t kRegExpParamOffset = 2 * target::kWordSize;
  const intptr_t kStringParamOffset = 1 * target::kWordSize;
  // start_index smi is located at offset 0.
 
  // Incoming registers:
  // R0: Function. (Will be reloaded with the specialized matcher function.)
  // R4: Arguments descriptor. (Will be preserved.)
  // R9: Unknown. (Must be GC safe on tail call.)
 
  // Load the specialized function pointer into R0. Leverage the fact the
  // string CIDs as well as stored function pointers are in sequence.
  __ ldr(R2, Address(SP, kRegExpParamOffset));
  __ ldr(R1, Address(SP, kStringParamOffset));
  __ LoadClassId(R1, R1);
  __ AddImmediate(R1, -kOneByteStringCid);
  __ add(R1, R2, Operand(R1, LSL, target::kWordSizeLog2));
  __ ldr(FUNCTION_REG, FieldAddress(R1, target::RegExp::function_offset(
                                            kOneByteStringCid, sticky)));
 
  // Registers are now set up for the lazy compile stub. It expects the function
  // in R0, the argument descriptor in R4, and IC-Data in R9.
  __ eor(R9, R9, Operand(R9));
 
  // Tail-call the function.
  __ ldr(CODE_REG, FieldAddress(FUNCTION_REG, target::Function::code_offset()));
  __ Branch(FieldAddress(FUNCTION_REG, target::Function::entry_point_offset()));
}
 
void AsmIntrinsifier::UserTag_defaultTag(Assembler* assembler,
                                         Label* normal_ir_body) {
  __ LoadIsolate(R0);
  __ ldr(R0, Address(R0, target::Isolate::default_tag_offset()));
  __ Ret();
}
 
void AsmIntrinsifier::Profiler_getCurrentTag(Assembler* assembler,
                                             Label* normal_ir_body) {
  __ LoadIsolate(R0);
  __ ldr(R0, Address(R0, target::Isolate::current_tag_offset()));
  __ Ret();
}
 
void AsmIntrinsifier::Timeline_isDartStreamEnabled(Assembler* assembler,
                                                   Label* normal_ir_body) {
#if !defined(SUPPORT_TIMELINE)
  __ LoadObject(R0, CastHandle<Object>(FalseObject()));
  __ Ret();
#else
  // Load TimelineStream*.
  __ ldr(R0, Address(THR, target::Thread::dart_stream_offset()));
  // Load uintptr_t from TimelineStream*.
  __ ldr(R0, Address(R0, target::TimelineStream::enabled_offset()));
  __ cmp(R0, Operand(0));
  __ LoadObject(R0, CastHandle<Object>(TrueObject()), NE);
  __ LoadObject(R0, CastHandle<Object>(FalseObject()), EQ);
  __ Ret();
#endif
}
 
void AsmIntrinsifier::Timeline_getNextTaskId(Assembler* assembler,
                                             Label* normal_ir_body) {
#if !defined(SUPPORT_TIMELINE)
  __ LoadImmediate(R0, target::ToRawSmi(0));
  __ Ret();
#else
  __ ldr(R1, Address(THR, target::Thread::next_task_id_offset()));
  __ ldr(R2, Address(THR, target::Thread::next_task_id_offset() + 4));
  __ SmiTag(R0, R1);  // Ignore loss of precision.
  __ adds(R1, R1, Operand(1));
  __ adcs(R2, R2, Operand(0));
  __ str(R1, Address(THR, target::Thread::next_task_id_offset()));
  __ str(R2, Address(THR, target::Thread::next_task_id_offset() + 4));
  __ Ret();
#endif
}
 
#undef __
 
}  // namespace compiler
}  // namespace dart
 
#endif  // defined(TARGET_ARCH_ARM)