Prefer loading Smi 0 instead of null into a runtime call result slot.

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 268 matching lines @@
 }
 
 
 // Input parameters:
 //   R4: arguments descriptor array.
 void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
   // Setup space on stack for return value and preserve arguments descriptor.
-  __ LoadObject(R0, Object::null_object());
+  __ LoadImmediate(R0, 0);
   __ PushList((1 << R0) | (1 << R4));
   __ CallRuntime(kPatchStaticCallRuntimeEntry, 0);
   // Get Code object result and restore arguments descriptor array.
   __ PopList((1 << R0) | (1 << R4));
   // Remove the stub frame.
   __ LeaveStubFrame();
   // Jump to the dart function.
   __ mov(CODE_REG, Operand(R0));
   __ ldr(R0, FieldAddress(R0, Code::entry_point_offset()));
   __ bx(R0);
 }
 
 
 // Called from a static call only when an invalid code has been entered
 // (invalid because its function was optimized or deoptimized).
 // R4: arguments descriptor array.
 void StubCode::GenerateFixCallersTargetStub(Assembler* assembler) {
   // Load code pointer to this stub from the thread:
   // The one that is passed in, is not correct - it points to the code object
   // that needs to be replaced.
   __ ldr(CODE_REG, Address(THR, Thread::fix_callers_target_code_offset()));
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
   // Setup space on stack for return value and preserve arguments descriptor.
-  __ LoadObject(R0, Object::null_object());
+  __ LoadImmediate(R0, 0);
   __ PushList((1 << R0) | (1 << R4));
   __ CallRuntime(kFixCallersTargetRuntimeEntry, 0);
   // Get Code object result and restore arguments descriptor array.
   __ PopList((1 << R0) | (1 << R4));
   // Remove the stub frame.
   __ LeaveStubFrame();
   // Jump to the dart function.
   __ mov(CODE_REG, Operand(R0));
   __ ldr(R0, FieldAddress(R0, Code::entry_point_offset()));
   __ bx(R0);
 }
 
 
 // Called from object allocate instruction when the allocation stub has been
 // disabled.
 void StubCode::GenerateFixAllocationStubTargetStub(Assembler* assembler) {
   // Load code pointer to this stub from the thread:
   // The one that is passed in, is not correct - it points to the code object
   // that needs to be replaced.
   __ ldr(CODE_REG, Address(THR, Thread::fix_allocation_stub_code_offset()));
   __ EnterStubFrame();
   // Setup space on stack for return value.
-  __ LoadObject(R0, Object::null_object());
+  __ LoadImmediate(R0, 0);
   __ Push(R0);
   __ CallRuntime(kFixAllocationStubTargetRuntimeEntry, 0);
   // Get Code object result.
   __ Pop(R0);
   // Remove the stub frame.
   __ LeaveStubFrame();
   // Jump to the dart function.
   __ mov(CODE_REG, Operand(R0));
   __ ldr(R0, FieldAddress(R0, Code::entry_point_offset()));
   __ bx(R0);
@@ skipping 186 matching lines @@
   __ Comment("NoSuchMethodDispatch");
   // When lazily generated invocation dispatchers are disabled, the
   // miss-handler may return null.
   __ CompareObject(R0, Object::null_object());
   __ b(call_target_function, NE);
   __ EnterStubFrame();
   // Load the receiver.
   __ ldr(R2, FieldAddress(R4, ArgumentsDescriptor::count_offset()));
   __ add(IP, FP, Operand(R2, LSL, 1));  // R2 is Smi.
   __ ldr(R8, Address(IP, kParamEndSlotFromFp * kWordSize));
-  __ PushObject(Object::null_object());
+  __ LoadImmediate(IP, 0);
+  __ Push(IP);  // Result slot.
   __ Push(R8);  // Receiver.
   __ Push(R9);  // ICData/MegamorphicCache.
   __ Push(R4);  // Arguments descriptor.
   // R2: Smi-tagged arguments array length.
   PushArgumentsArray(assembler);
   const intptr_t kNumArgs = 4;
   __ CallRuntime(kInvokeNoSuchMethodDispatcherRuntimeEntry, kNumArgs);
   __ Drop(4);
   __ Pop(R0);  // Return value.
   __ LeaveStubFrame();
   __ Ret();
 }
 
 
 void StubCode::GenerateMegamorphicMissStub(Assembler* assembler) {
   __ EnterStubFrame();
 
   // Load the receiver.
   __ ldr(R2, FieldAddress(R4, ArgumentsDescriptor::count_offset()));
   __ add(IP, FP, Operand(R2, LSL, 1));  // R2 is Smi.
   __ ldr(R8, Address(IP, kParamEndSlotFromFp * kWordSize));
 
   // Preserve IC data and arguments descriptor.
   __ PushList((1 << R4) | (1 << R9));
 
-  __ LoadObject(IP, Object::null_object());
-  __ Push(IP);  // result
+  __ LoadImmediate(IP, 0);
+  __ Push(IP);  // result slot
   __ Push(R8);  // receiver
   __ Push(R9);  // ICData
   __ Push(R4);  // arguments descriptor
   __ CallRuntime(kMegamorphicCacheMissHandlerRuntimeEntry, 3);
   // Remove arguments.
   __ Drop(3);
   __ Pop(R0);  // Get result into R0 (target function).
 
   // Restore IC data and arguments descriptor.
   __ PopList((1 << R4) | (1 << R9));
@@ skipping 120 matching lines @@
   __ AddImmediate(R4, R0, sizeof(RawArray) - kHeapObjectTag);
   __ InitializeFieldsNoBarrier(R0, R4, NOTFP, R8, R9);
   __ Ret();  // Returns the newly allocated object in R0.
   // Unable to allocate the array using the fast inline code, just call
   // into the runtime.
   __ Bind(&slow_case);
 
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
-  __ LoadObject(IP, Object::null_object());
+  __ LoadImmediate(IP, 0);
   // Setup space on stack for return value.
   // Push array length as Smi and element type.
   __ PushList((1 << R1) | (1 << R2) | (1 << IP));
   __ CallRuntime(kAllocateArrayRuntimeEntry, 2);
   // Pop arguments; result is popped in IP.
   __ PopList((1 << R1) | (1 << R2) | (1 << IP));  // R2 is restored.
   __ mov(R0, Operand(IP));
   __ LeaveStubFrame();
   __ Ret();
 }
@@ skipping 221 matching lines @@
     // Done allocating and initializing the context.
     // R0: new object.
     __ Ret();
 
     __ Bind(&slow_case);
   }
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
   // Setup space on stack for return value.
-  __ LoadObject(R2, Object::null_object());
+  __ LoadImmediate(R2, 0);
   __ SmiTag(R1);
   __ PushList((1 << R1) | (1 << R2));
   __ CallRuntime(kAllocateContextRuntimeEntry, 1);  // Allocate context.
   __ Drop(1);  // Pop number of context variables argument.
   __ Pop(R0);  // Pop the new context object.
   // R0: new object
   // Restore the frame pointer.
   __ LeaveStubFrame();
   __ Ret();
 }
@@ skipping 220 matching lines @@
   __ EnterStubFrame();
 
   // Load the receiver.
   __ ldr(R2, FieldAddress(R4, ArgumentsDescriptor::count_offset()));
   __ add(IP, FP, Operand(R2, LSL, 1));  // R2 is Smi.
   __ ldr(R8, Address(IP, kParamEndSlotFromFp * kWordSize));
 
   // Push space for the return value.
   // Push the receiver.
   // Push arguments descriptor array.
-  __ LoadObject(IP, Object::null_object());
+  __ LoadImmediate(IP, 0);
   __ PushList((1 << R4) | (1 << R8) | (1 << IP));
 
   // R2: Smi-tagged arguments array length.
   PushArgumentsArray(assembler);
 
   const intptr_t kNumArgs = 3;
   __ CallRuntime(kInvokeClosureNoSuchMethodRuntimeEntry, kNumArgs);
   // noSuchMethod on closures always throws an error, so it will never return.
   __ bkpt(0);
 }
@@ skipping 208 matching lines @@
   __ b(&loop, NE);
 
   __ Comment("IC miss");
   // Compute address of arguments.
   // NOTFP: argument_count - 1 (smi).
   __ add(NOTFP, SP, Operand(NOTFP, LSL, 1));  // NOTFP is Smi.
   // NOTFP: address of receiver.
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
-  __ LoadObject(R0, Object::null_object());
+  __ LoadImmediate(R0, 0);
   // Preserve IC data object and arguments descriptor array and
   // setup space on stack for result (target code object).
   __ PushList((1 << R0) | (1 << R4) | (1 << R9));
   // Push call arguments.
   for (intptr_t i = 0; i < num_args; i++) {
     __ LoadFromOffset(kWord, IP, NOTFP, -i * kWordSize);
     __ Push(IP);
   }
   // Pass IC data object.
   __ Push(R9);
@@ skipping 212 matching lines @@
 
   __ ldr(CODE_REG, FieldAddress(R0, Function::code_offset()));
   __ ldr(R2, FieldAddress(R0, Function::entry_point_offset()));
   __ bx(R2);
 }
 
 
 // R9: Contains an ICData.
 void StubCode::GenerateICCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
-  __ LoadObject(R0, Object::null_object());
+  __ LoadImmediate(R0, 0);
   // Preserve arguments descriptor and make room for result.
   __ PushList((1 << R0) | (1 << R9));
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
   __ PopList((1 << R0) | (1 << R9));
   __ LeaveStubFrame();
   __ mov(CODE_REG, Operand(R0));
   __ ldr(R0, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ bx(R0);
 }
 
 
 void StubCode::GenerateRuntimeCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
-  __ LoadObject(R0, Object::null_object());
+  __ LoadImmediate(R0, 0);
   // Make room for result.
   __ PushList((1 << R0));
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
   __ PopList((1 << CODE_REG));
   __ LeaveStubFrame();
   __ ldr(R0, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ bx(R0);
 }
 
 
@@ skipping 161 matching lines @@
   __ bx(LR);  // Jump to the exception handler code.
 }
 
 
 // Calls to the runtime to optimize the given function.
 // R8: function to be reoptimized.
 // R4: argument descriptor (preserved).
 void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ Push(R4);
-  __ LoadObject(IP, Object::null_object());
+  __ LoadImmediate(IP, 0);
   __ Push(IP);  // Setup space on stack for return value.
   __ Push(R8);
   __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry, 1);
   __ Pop(R0);  // Discard argument.
   __ Pop(R0);  // Get Code object
   __ Pop(R4);  // Restore argument descriptor.
   __ LeaveStubFrame();
   __ mov(CODE_REG, Operand(R0));
   __ ldr(R0, FieldAddress(R0, Code::entry_point_offset()));
   __ bx(R0);
@@ skipping 260 matching lines @@
 
 // Called from switchable IC calls.
 //  R0: receiver
 //  R9: UnlinkedCall
 void StubCode::GenerateUnlinkedCallStub(Assembler* assembler) {
   __ NoMonomorphicCheckedEntry();
 
   __ EnterStubFrame();
   __ Push(R0);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ Push(R0);                           // Arg0: Receiver
-  __ Push(R9);                           // Arg1: UnlinkedCall
+  __ LoadImmediate(IP, 0);
+  __ Push(IP);  // Result slot
+  __ Push(R0);  // Arg0: Receiver
+  __ Push(R9);  // Arg1: UnlinkedCall
   __ CallRuntime(kUnlinkedCallRuntimeEntry, 2);
   __ Drop(2);
   __ Pop(R9);  // result = IC
 
   __ Pop(R0);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ ldr(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ ldr(R1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ bx(R1);
@@ skipping 20 matching lines @@
   __ b(&miss, GT);
 
   __ ldr(R1, FieldAddress(R9, SingleTargetCache::entry_point_offset()));
   __ ldr(CODE_REG, FieldAddress(R9, SingleTargetCache::target_offset()));
   __ bx(R1);
 
   __ Bind(&miss);
   __ EnterStubFrame();
   __ Push(R0);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ Push(R0);                           // Arg0: Receiver
+  __ LoadImmediate(IP, 0);
+  __ Push(IP);  // Result slot
+  __ Push(R0);  // Arg0: Receiver
   __ CallRuntime(kSingleTargetMissRuntimeEntry, 1);
   __ Drop(1);
   __ Pop(R9);  // result = IC
 
   __ Pop(R0);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ ldr(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ ldr(R1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ bx(R1);
 }
 
 
 // Called from the monomorphic checked entry.
 //  R0: receiver
 void StubCode::GenerateMonomorphicMissStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ Push(R0);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ Push(R0);                           // Arg0: Receiver
+  __ LoadImmediate(IP, 0);
+  __ Push(IP);  // Result slot
+  __ Push(R0);  // Arg0: Receiver
   __ CallRuntime(kMonomorphicMissRuntimeEntry, 1);
   __ Drop(1);
   __ Pop(R9);  // result = IC
 
   __ Pop(R0);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ ldr(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ ldr(R1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ bx(R1);
 }
 
 
 void StubCode::GenerateFrameAwaitingMaterializationStub(Assembler* assembler) {
   __ bkpt(0);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM