Cleanup of class id loading sequences.

runtime/vm/stub_code_x64.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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1253 matching lines @@
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Incorrect stub for IC data");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
   Label stepping, done_stepping;
   if (FLAG_enable_debugger) {
     // Check single stepping.
     __ movq(RAX, FieldAddress(CTX, Context::isolate_offset()));
-    __ movzxb(RAX, Address(RAX, Isolate::single_step_offset()));
-    __ cmpq(RAX, Immediate(0));
+    __ cmpb(Address(RAX, Isolate::single_step_offset()), Immediate(0));
     __ j(NOT_EQUAL, &stepping);
     __ Bind(&done_stepping);
   }
 
   // Load arguments descriptor into R10.
   __ movq(R10, FieldAddress(RBX, ICData::arguments_descriptor_offset()));
   // Loop that checks if there is an IC data match.
   Label loop, update, test, found;
   // RBX: IC data object (preserved).
   __ movq(R12, FieldAddress(RBX, ICData::ic_data_offset()));
   // R12: ic_data_array with check entries: classes and target functions.
   __ leaq(R12, FieldAddress(R12, Array::data_offset()));
   // R12: points directly to the first ic data array element.
 
   // Get the receiver's class ID (first read number of arguments from
   // arguments descriptor array and then access the receiver from the stack).
   __ movq(RAX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
-  __ movq(RAX, Address(RSP, RAX, TIMES_4, 0));  // RAX (argument count) is Smi.
-  __ LoadTaggedClassIdMayBeSmi(RAX, RAX);
+  __ movq(R13, Address(RSP, RAX, TIMES_4, 0));  // RAX (argument count) is Smi.
+  __ LoadTaggedClassIdMayBeSmi(RAX, R13);
   // RAX: receiver's class ID as smi.
   __ movq(R13, Address(R12, 0));  // First class ID (Smi) to check.
   __ jmp(&test);
 
   __ Bind(&loop);
   for (int i = 0; i < num_args; i++) {
     if (i > 0) {
       // If not the first, load the next argument's class ID.
       __ movq(RAX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
-      __ movq(RAX, Address(RSP, RAX, TIMES_4, - i * kWordSize));
-      __ LoadTaggedClassIdMayBeSmi(RAX, RAX);
+      __ movq(R13, Address(RSP, RAX, TIMES_4, - i * kWordSize));
+      __ LoadTaggedClassIdMayBeSmi(RAX, R13);
       // RAX: next argument class ID (smi).
       __ movq(R13, Address(R12, i * kWordSize));
       // R13: next class ID to check (smi).
     }
     __ cmpq(RAX, R13);  // Class id match?
     if (i < (num_args - 1)) {
       __ j(NOT_EQUAL, &update);  // Continue.
     } else {
       // Last check, all checks before matched.
       __ j(EQUAL, &found);  // Break.
     }
   }
   __ Bind(&update);
   // Reload receiver class ID.  It has not been destroyed when num_args == 1.
   if (num_args > 1) {
     __ movq(RAX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
-    __ movq(RAX, Address(RSP, RAX, TIMES_4, 0));
-    __ LoadTaggedClassIdMayBeSmi(RAX, RAX);
+    __ movq(R13, Address(RSP, RAX, TIMES_4, 0));
+    __ LoadTaggedClassIdMayBeSmi(RAX, R13);
   }
 
   const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
   __ addq(R12, Immediate(entry_size));  // Next entry.
   __ movq(R13, Address(R12, 0));  // Next class ID.
 
   __ Bind(&test);
   __ cmpq(R13, Immediate(Smi::RawValue(kIllegalCid)));  // Done?
   __ j(NOT_EQUAL, &loop, Assembler::kNearJump);
 
@@ skipping 577 matching lines @@
 
   __ movq(left, Address(RSP, 2 * kWordSize));
   __ movq(right, Address(RSP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64