Clarify result returned by remainder intrinsics.

runtime/vm/intrinsifier_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 348 matching lines @@
 
 
 // Optimizations:
 // - result is 0 if:
 //   - left is 0
 //   - left equals right
 // - result is left if
 //   - left > 0 && left < right
 // R1: Tagged left (dividend).
 // R0: Tagged right (divisor).
-// Returns with result in R0, OR:
-//   R1: Untagged result (remainder).
+// Returns:
+//   R1: Untagged fallthrough result (remainder to be adjusted), or
+//   R0: Tagged return result (remainder).
 static void EmitRemainderOperation(Assembler* assembler) {
   Label return_zero, modulo;
   const Register left = R1;
   const Register right = R0;
   const Register result = R1;
   const Register tmp = R2;
   ASSERT(left == result);
 
   // Check for quick zero results.
   __ CompareRegisters(left, ZR);
@@ skipping 1624 matching lines @@
   Isolate* isolate = Isolate::Current();
   __ LoadImmediate(R1, reinterpret_cast<uword>(isolate), kNoPP);
   // Set return value to Isolate::current_tag_.
   __ ldr(R0, Address(R1, Isolate::current_tag_offset()));
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64