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

runtime/vm/stub_code_mips.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_MIPS)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 281 matching lines @@
 
 // Input parameters:
 //   S4: arguments descriptor array.
 void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
   __ Comment("CallStaticFunctionStub");
   __ EnterStubFrame();
   // Setup space on stack for return value and preserve arguments descriptor.
 
   __ addiu(SP, SP, Immediate(-2 * kWordSize));
   __ sw(S4, Address(SP, 1 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 0 * kWordSize));
+  __ sw(ZR, Address(SP, 0 * kWordSize));
 
   __ CallRuntime(kPatchStaticCallRuntimeEntry, 0);
   __ Comment("CallStaticFunctionStub return");
 
   // Get Code object result and restore arguments descriptor array.
   __ lw(CODE_REG, Address(SP, 0 * kWordSize));
   __ lw(S4, Address(SP, 1 * kWordSize));
   __ addiu(SP, SP, Immediate(2 * kWordSize));
 
   __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
@@ skipping 10 matching lines @@
   // 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.
   __ lw(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.
   __ addiu(SP, SP, Immediate(-2 * kWordSize));
   __ sw(S4, Address(SP, 1 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 0 * kWordSize));
+  __ sw(ZR, Address(SP, 0 * kWordSize));
   __ CallRuntime(kFixCallersTargetRuntimeEntry, 0);
   // Get Code object result and restore arguments descriptor array.
   __ lw(CODE_REG, Address(SP, 0 * kWordSize));
   __ lw(S4, Address(SP, 1 * kWordSize));
   __ addiu(SP, SP, Immediate(2 * kWordSize));
 
   // Jump to the dart function.
   __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
 
   // Remove the stub frame.
   __ LeaveStubFrameAndReturn(T0);
 }
 
 
 // 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.
   __ lw(CODE_REG, Address(THR, Thread::fix_allocation_stub_code_offset()));
   __ EnterStubFrame();
   // Setup space on stack for return value.
   __ addiu(SP, SP, Immediate(-1 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 0 * kWordSize));
+  __ sw(ZR, Address(SP, 0 * kWordSize));
   __ CallRuntime(kFixAllocationStubTargetRuntimeEntry, 0);
   // Get Code object result.
   __ lw(CODE_REG, Address(SP, 0 * kWordSize));
   __ addiu(SP, SP, Immediate(1 * kWordSize));
 
   // Jump to the dart function.
   __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
 
   // Remove the stub frame.
   __ LeaveStubFrameAndReturn(T0);
@@ skipping 185 matching lines @@
   __ sll(TMP, A1, 1);  // A1 is a Smi.
   __ addu(TMP, FP, TMP);
   __ lw(T6, Address(TMP, kParamEndSlotFromFp * kWordSize));
 
   // Push space for the return value.
   // Push the receiver.
   // Push ICData/MegamorphicCache object.
   // Push arguments descriptor array.
   // Push original arguments array.
   __ addiu(SP, SP, Immediate(-4 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 3 * kWordSize));
+  __ sw(ZR, Address(SP, 3 * kWordSize));
   __ sw(T6, Address(SP, 2 * kWordSize));
   __ sw(S5, Address(SP, 1 * kWordSize));
   __ sw(S4, Address(SP, 0 * kWordSize));
   // A1: Smi-tagged arguments array length.
   PushArgumentsArray(assembler);
   const intptr_t kNumArgs = 4;
   __ CallRuntime(kInvokeNoSuchMethodDispatcherRuntimeEntry, kNumArgs);
   __ lw(V0, Address(SP, 4 * kWordSize));  // Return value.
   __ addiu(SP, SP, Immediate(5 * kWordSize));
   __ LeaveStubFrame();
@@ skipping 12 matching lines @@
 
   // Preserve IC data and arguments descriptor.
   __ addiu(SP, SP, Immediate(-6 * kWordSize));
   __ sw(S5, Address(SP, 5 * kWordSize));
   __ sw(S4, Address(SP, 4 * kWordSize));
 
   // Push space for the return value.
   // Push the receiver.
   // Push IC data object.
   // Push arguments descriptor array.
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 3 * kWordSize));
+  __ sw(ZR, Address(SP, 3 * kWordSize));
   __ sw(T6, Address(SP, 2 * kWordSize));
   __ sw(S5, Address(SP, 1 * kWordSize));
   __ sw(S4, Address(SP, 0 * kWordSize));
 
   __ CallRuntime(kMegamorphicCacheMissHandlerRuntimeEntry, 3);
 
   __ lw(T0, Address(SP, 3 * kWordSize));  // Get result function.
   __ lw(S4, Address(SP, 4 * kWordSize));  // Restore argument descriptor.
   __ lw(S5, Address(SP, 5 * kWordSize));  // Restore IC data.
   __ addiu(SP, SP, Immediate(6 * kWordSize));
@@ skipping 137 matching lines @@
 
   // 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();
   // Setup space on stack for return value.
   // Push array length as Smi and element type.
   __ addiu(SP, SP, Immediate(-3 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 2 * kWordSize));
+  __ sw(ZR, Address(SP, 2 * kWordSize));
   __ sw(A1, Address(SP, 1 * kWordSize));
   __ sw(A0, Address(SP, 0 * kWordSize));
   __ CallRuntime(kAllocateArrayRuntimeEntry, 2);
   __ Comment("AllocateArrayStub return");
   // Pop arguments; result is popped in IP.
   __ lw(V0, Address(SP, 2 * kWordSize));
   __ lw(A1, Address(SP, 1 * kWordSize));
   __ lw(A0, Address(SP, 0 * kWordSize));
   __ addiu(SP, SP, Immediate(3 * kWordSize));
 
@@ skipping 481 matching lines @@
   __ lw(A1, FieldAddress(S4, ArgumentsDescriptor::count_offset()));
   __ sll(TMP, A1, 1);  // A1 is a Smi.
   __ addu(TMP, FP, TMP);
   __ lw(T6, Address(TMP, kParamEndSlotFromFp * kWordSize));
 
   // Push space for the return value.
   // Push the receiver.
   // Push arguments descriptor array.
   const intptr_t kNumArgs = 3;
   __ addiu(SP, SP, Immediate(-kNumArgs * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 2 * kWordSize));
+  __ sw(ZR, Address(SP, 2 * kWordSize));
   __ sw(T6, Address(SP, 1 * kWordSize));
   __ sw(S4, Address(SP, 0 * kWordSize));
 
   // A1: Smi-tagged arguments array length.
   PushArgumentsArray(assembler);
 
   __ CallRuntime(kInvokeClosureNoSuchMethodRuntimeEntry, kNumArgs);
   // noSuchMethod on closures always throws an error, so it will never return.
   __ break_(0);
 }
@@ skipping 242 matching lines @@
   // T1: address of receiver.
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
   // Preserve IC data object and arguments descriptor array and
   // setup space on stack for result (target code object).
   int num_slots = num_args + 4;
   __ addiu(SP, SP, Immediate(-num_slots * kWordSize));
   __ sw(S5, Address(SP, (num_slots - 1) * kWordSize));
   __ sw(S4, Address(SP, (num_slots - 2) * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, (num_slots - 3) * kWordSize));
+  __ sw(ZR, Address(SP, (num_slots - 3) * kWordSize));
   // Push call arguments.
   for (intptr_t i = 0; i < num_args; i++) {
     __ lw(TMP, Address(T1, -i * kWordSize));
     __ sw(TMP, Address(SP, (num_slots - i - 4) * kWordSize));
   }
   // Pass IC data object.
   __ sw(S5, Address(SP, (num_slots - num_args - 4) * kWordSize));
   __ CallRuntime(handle_ic_miss, num_args + 1);
   __ Comment("NArgsCheckInlineCacheStub return");
   // Pop returned function object into T3.
@@ skipping 231 matching lines @@
   __ jr(T2);
 }
 
 
 // S5: Contains an ICData.
 void StubCode::GenerateICCallBreakpointStub(Assembler* assembler) {
   __ Comment("ICCallBreakpoint stub");
   __ EnterStubFrame();
   __ addiu(SP, SP, Immediate(-2 * kWordSize));
   __ sw(S5, Address(SP, 1 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 0 * kWordSize));
+  __ sw(ZR, Address(SP, 0 * kWordSize));
 
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
 
   __ lw(S5, Address(SP, 1 * kWordSize));
   __ lw(CODE_REG, Address(SP, 0 * kWordSize));
   __ addiu(SP, SP, Immediate(2 * kWordSize));
   __ LeaveStubFrame();
   __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ jr(T0);
 }
 
 
 void StubCode::GenerateRuntimeCallBreakpointStub(Assembler* assembler) {
   __ Comment("RuntimeCallBreakpoint stub");
   __ EnterStubFrame();
   __ addiu(SP, SP, Immediate(-1 * kWordSize));
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 0 * kWordSize));
+  __ sw(ZR, Address(SP, 0 * kWordSize));
 
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
 
   __ lw(CODE_REG, Address(SP, 0 * kWordSize));
   __ addiu(SP, SP, Immediate(3 * kWordSize));
   __ LeaveStubFrame();
   __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ jr(T0);
 }
 
@@ skipping 175 matching lines @@
 
 // Calls to the runtime to optimize the given function.
 // T0: function to be reoptimized.
 // S4: argument descriptor (preserved).
 void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
   __ Comment("OptimizeFunctionStub");
   __ EnterStubFrame();
   __ addiu(SP, SP, Immediate(-3 * kWordSize));
   __ sw(S4, Address(SP, 2 * kWordSize));
   // Setup space on stack for return value.
-  __ LoadObject(TMP, Object::null_object());
-  __ sw(TMP, Address(SP, 1 * kWordSize));
+  __ sw(ZR, Address(SP, 1 * kWordSize));
   __ sw(T0, Address(SP, 0 * kWordSize));
   __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry, 1);
   __ Comment("OptimizeFunctionStub return");
   __ lw(CODE_REG, Address(SP, 1 * kWordSize));  // Get Code object
   __ lw(S4, Address(SP, 2 * kWordSize));  // Restore argument descriptor.
   __ addiu(SP, SP, Immediate(3 * kWordSize));  // Discard argument.
 
   __ lw(T0, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ LeaveStubFrameAndReturn(T0);
   __ break_(0);
@@ skipping 272 matching lines @@
 
 // Called from switchable IC calls.
 //  T0: receiver
 //  S5: SingleTargetCache
 void StubCode::GenerateUnlinkedCallStub(Assembler* assembler) {
   __ NoMonomorphicCheckedEntry();
 
   __ EnterStubFrame();
   __ Push(T0);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ Push(T0);                           // Arg0: Receiver
-  __ Push(S5);                           // Arg1: UnlinkedCall
+  __ Push(ZR);  // Result slot.
+  __ Push(T0);  // Arg0: Receiver
+  __ Push(S5);  // Arg1: UnlinkedCall
   __ CallRuntime(kUnlinkedCallRuntimeEntry, 2);
   __ Drop(2);
   __ Pop(S5);  // result = IC
 
   __ Pop(T0);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ lw(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ lw(T1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ jr(T1);
@@ skipping 18 matching lines @@
   __ BranchUnsignedGreater(T1, T3, &miss);
 
   __ lw(T1, FieldAddress(S5, SingleTargetCache::entry_point_offset()));
   __ lw(CODE_REG, FieldAddress(S5, SingleTargetCache::target_offset()));
   __ jr(T1);
 
   __ Bind(&miss);
   __ EnterStubFrame();
   __ Push(T0);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ Push(T0);                           // Arg0: Receiver
+  __ Push(ZR);  // Result slot.
+  __ Push(T0);  // Arg0: Receiver
   __ CallRuntime(kSingleTargetMissRuntimeEntry, 1);
   __ Drop(1);
   __ Pop(S5);  // result = IC
 
   __ Pop(T0);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ lw(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ lw(T1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ jr(T1);
 }
 
 
 // Called from the monomorphic checked entry.
 //  T0: receiver
 void StubCode::GenerateMonomorphicMissStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ Push(T0);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ Push(T0);                           // Arg0: Receiver
+  __ Push(ZR);  // Result slot.
+  __ Push(T0);  // Arg0: Receiver
   __ CallRuntime(kMonomorphicMissRuntimeEntry, 1);
   __ Drop(1);
   __ Pop(S5);  // result = IC
 
   __ Pop(T0);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ lw(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ lw(T1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ jr(T1);
 }
 
 
 void StubCode::GenerateFrameAwaitingMaterializationStub(Assembler* assembler) {
   __ break_(0);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS