Implement bigint intrinsics on arm64.

runtime/vm/intrinsifier_arm.cc

 // 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_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1175 matching lines @@
   // c:   R7:R6
   // t:   R2:R1:R0 (not live at loop entry)
   // n:   R8
 
   // uint32_t xi = *xip++
   __ ldr(R2, Address(R4, Bigint::kBytesPerDigit, Address::PostIndex));
 
   // uint32_t aj = *ajp
   __ ldr(R1, Address(R5, 0));
 
-  // uint96_t t = R2:R1:R0 = 2*x*xi + aj + c
+  // uint96_t t = R7:R6:R0 = 2*x*xi + aj + c
   __ mov(R0, Operand(0));
   __ umaal(R0, R1, R2, R3);  // R1:R0 = R3*R2 + R1 + R0 = x*xi + aj + 0.
   __ umlal(R6, R7, R2, R3);  // R7:R6 += R3*R2; c += x*xi.
   __ adds(R0, R0, Operand(R6));
   __ adcs(R6, R1, Operand(R7));
   __ mov(R7, Operand(0));
   __ adc(R7, R7, Operand(0));  // R7:R6:R0 = R1:R0 + R7:R6 = 2*x*xi + aj + c.
 
   // *ajp++ = low32(t) = R0
   __ str(R0, Address(R5, Bigint::kBytesPerDigit, Address::PostIndex));
@@ skipping 14 matching lines @@
   // *(ajp + 1) = high32(t) = R7
   __ strd(R6, Address(R5, 0));
 
   __ Bind(&x_zero);
   // Returning Object::null() is not required, since this method is private.
   __ Ret();
 }
 
 
 void Intrinsifier::Bigint_estQuotientDigit(Assembler* assembler) {
-  // TODO(regis): Implement.
+  // No unsigned 64-bit / 32-bit divide instruction.
 }
 
 
 void Intrinsifier::Montgomery_mulMod(Assembler* assembler) {
   if (TargetCPUFeatures::arm_version() != ARMv7) {
     return;
   }
   // Pseudo code:
   // static void _mulMod(Uint32List args, Uint32List digits, int i) {
   //   uint32_t rho = args[_RHO];  // _RHO == 0.
@@ skipping 762 matching lines @@
   Isolate* isolate = Isolate::Current();
   __ LoadImmediate(R1, reinterpret_cast<uword>(isolate));
   // Set return value to Isolate::current_tag_.
   __ ldr(R0, Address(R1, Isolate::current_tag_offset()));
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM