Add LoadTaggedClassIdMayBeSmi to assembly and improve performance of inline cache stubs.

runtime/vm/stub_code_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"
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 1265 matching lines @@
     __ Pop(R5);
     __ LeaveStubFrame();
     __ Bind(&not_stepping);
   }
 
   // Load arguments descriptor into R4.
   __ ldr(R4, FieldAddress(R5, ICData::arguments_descriptor_offset()));
   // Preserve return address, since LR is needed for subroutine call.
   __ mov(R8, Operand(LR));
   // Loop that checks if there is an IC data match.
-  Label loop, update, test, found, get_class_id_as_smi;
+  Label loop, update, test, found;
   // R5: IC data object (preserved).
   __ ldr(R6, FieldAddress(R5, ICData::ic_data_offset()));
   // R6: ic_data_array with check entries: classes and target functions.
   __ AddImmediate(R6, R6, Array::data_offset() - kHeapObjectTag);
   // R6: 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).
   __ ldr(R7, FieldAddress(R4, ArgumentsDescriptor::count_offset()));
   __ sub(R7, R7, Operand(Smi::RawValue(1)));
   __ ldr(R0, Address(SP, R7, LSL, 1));  // R7 (argument_count - 1) is smi.
-  __ bl(&get_class_id_as_smi);
+  __ LoadTaggedClassIdMayBeSmi(R0, R0);
   // R7: argument_count - 1 (smi).
   // R0: receiver's class ID (smi).
   __ ldr(R1, Address(R6, 0));  // First class id (smi) to check.
   __ b(&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.
       __ AddImmediate(R0, R7, Smi::RawValue(-i));
       __ ldr(R0, Address(SP, R0, LSL, 1));
-      __ bl(&get_class_id_as_smi);
+      __ LoadTaggedClassIdMayBeSmi(R0, R0);
       // R0: next argument class ID (smi).
       __ LoadFromOffset(kWord, R1, R6, i * kWordSize);
       // R1: next class ID to check (smi).
     }
     __ cmp(R0, Operand(R1));  // Class id match?
     if (i < (num_args - 1)) {
       __ b(&update, NE);  // Continue.
     } else {
       // Last check, all checks before matched.
       __ mov(LR, Operand(R8), EQ);  // Restore return address if found.
       __ b(&found, EQ);  // Break.
     }
   }
   __ Bind(&update);
   // Reload receiver class ID.  It has not been destroyed when num_args == 1.
   if (num_args > 1) {
     __ ldr(R0, Address(SP, R7, LSL, 1));
-    __ bl(&get_class_id_as_smi);
+    __ LoadTaggedClassIdMayBeSmi(R0, R0);
   }
 
   const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
   __ AddImmediate(R6, entry_size);  // Next entry.
   __ ldr(R1, Address(R6, 0));  // Next class ID.
 
   __ Bind(&test);
   __ CompareImmediate(R1, Smi::RawValue(kIllegalCid));  // Done?
   __ b(&loop, NE);
 
@@ skipping 39 matching lines @@
   __ StoreToOffset(kWord, R1, R6, count_offset);
   __ b(&call_target_function, VC);  // No overflow.
   __ LoadImmediate(R1, Smi::RawValue(Smi::kMaxValue));
   __ StoreToOffset(kWord, R1, R6, count_offset);
 
   __ Bind(&call_target_function);
   // R0: target function.
   __ ldr(R2, FieldAddress(R0, Function::instructions_offset()));
   __ AddImmediate(R2, Instructions::HeaderSize() - kHeapObjectTag);
   __ bx(R2);
-
-  // Instance in R0, return its class-id in R0 as Smi.
-  __ Bind(&get_class_id_as_smi);
-
-  // Test if Smi -> load Smi class for comparison.
-  __ tst(R0, Operand(kSmiTagMask));
-  __ mov(R0, Operand(Smi::RawValue(kSmiCid)), EQ);
-  __ bx(LR, EQ);
-  __ LoadClassId(R0, R0);
-  __ SmiTag(R0);
-  __ bx(LR);
 }
 
 
 // Use inline cache data array to invoke the target or continue in inline
 // cache miss handler. Stub for 1-argument check (receiver class).
 //  LR: return address.
 //  R5: inline cache data object.
 // Inline cache data object structure:
 // 0: function-name
 // 1: N, number of arguments checked.
@@ skipping 445 matching lines @@
   const Register right = R0;
   __ ldr(left, Address(SP, 1 * kWordSize));
   __ ldr(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM