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

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 243 matching lines @@
   __ ret();
 }
 
 
 // Input parameters:
 //   R10: arguments descriptor array.
 void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ pushq(R10);  // Preserve arguments descriptor array.
   // Setup space on stack for return value.
-  __ PushObject(Object::null_object());
+  __ pushq(Immediate(0));
   __ CallRuntime(kPatchStaticCallRuntimeEntry, 0);
   __ popq(CODE_REG);  // Get Code object result.
   __ popq(R10);  // Restore arguments descriptor array.
   // Remove the stub frame as we are about to jump to the dart function.
   __ LeaveStubFrame();
 
   __ movq(RBX, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ jmp(RBX);
 }
 
 
 // Called from a static call only when an invalid code has been entered
 // (invalid because its function was optimized or deoptimized).
 // R10: 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.
   __ movq(CODE_REG, Address(THR, Thread::fix_callers_target_code_offset()));
   __ EnterStubFrame();
   __ pushq(R10);  // Preserve arguments descriptor array.
   // Setup space on stack for return value.
-  __ PushObject(Object::null_object());
+  __ pushq(Immediate(0));
   __ CallRuntime(kFixCallersTargetRuntimeEntry, 0);
   __ popq(CODE_REG);  // Get Code object.
   __ popq(R10);  // Restore arguments descriptor array.
   __ movq(RAX, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ LeaveStubFrame();
   __ jmp(RAX);
   __ int3();
 }
 
 
 // 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.
   __ movq(CODE_REG, Address(THR, Thread::fix_allocation_stub_code_offset()));
   __ EnterStubFrame();
   // Setup space on stack for return value.
-  __ PushObject(Object::null_object());
+  __ pushq(Immediate(0));
   __ CallRuntime(kFixAllocationStubTargetRuntimeEntry, 0);
   __ popq(CODE_REG);  // Get Code object.
   __ movq(RAX, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ LeaveStubFrame();
   __ jmp(RAX);
   __ int3();
 }
 
 
 // Input parameters:
@@ skipping 180 matching lines @@
   __ Comment("NoSuchMethodDispatch");
   // When lazily generated invocation dispatchers are disabled, the
   // miss-handler may return null.
   __ CompareObject(RAX, Object::null_object());
   __ j(NOT_EQUAL, call_target_function);
   __ EnterStubFrame();
   // Load the receiver.
   __ movq(RDI, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   __ movq(RAX, Address(
       RBP, RDI, TIMES_HALF_WORD_SIZE, kParamEndSlotFromFp * kWordSize));
-  __ PushObject(Object::null_object());  // Setup space on stack for result.
+  __ pushq(Immediate(0));  // Setup space on stack for result.
   __ pushq(RAX);  // Receiver.
   __ pushq(RBX);  // ICData/MegamorphicCache.
   __ pushq(R10);  // Arguments descriptor array.
   __ movq(R10, RDI);
   // EDX: Smi-tagged arguments array length.
   PushArgumentsArray(assembler);
   const intptr_t kNumArgs = 4;
   __ CallRuntime(kInvokeNoSuchMethodDispatcherRuntimeEntry, kNumArgs);
   __ Drop(4);
   __ popq(RAX);  // Return value.
   __ LeaveStubFrame();
   __ ret();
 }
 
 
 void StubCode::GenerateMegamorphicMissStub(Assembler* assembler) {
   __ EnterStubFrame();
   // Load the receiver into RAX.  The argument count in the arguments
   // descriptor in R10 is a smi.
   __ movq(RAX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   // Three words (saved pp, saved fp, stub's pc marker)
   // in the stack above the return address.
   __ movq(RAX, Address(RSP, RAX, TIMES_4,
                        kSavedAboveReturnAddress * kWordSize));
   // Preserve IC data and arguments descriptor.
   __ pushq(RBX);
   __ pushq(R10);
 
   // Space for the result of the runtime call.
-  __ PushObject(Object::null_object());
+  __ pushq(Immediate(0));
   __ pushq(RAX);  // Receiver.
   __ pushq(RBX);  // IC data.
   __ pushq(R10);  // Arguments descriptor.
   __ CallRuntime(kMegamorphicCacheMissHandlerRuntimeEntry, 3);
   // Discard arguments.
   __ popq(RAX);
   __ popq(RAX);
   __ popq(RAX);
   __ popq(RAX);  // Return value from the runtime call (function).
   __ popq(R10);  // Restore arguments descriptor.
@@ skipping 126 matching lines @@
   __ Bind(&done);
   __ ret();  // returns the newly allocated object in RAX.
 
   // 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.
-  __ PushObject(Object::null_object());
+  __ pushq(Immediate(0));
   __ pushq(R10);  // Array length as Smi.
   __ pushq(RBX);  // Element type.
   __ CallRuntime(kAllocateArrayRuntimeEntry, 2);
   __ popq(RAX);  // Pop element type argument.
   __ popq(R10);  // Pop array length argument.
   __ popq(RAX);  // Pop return value from return slot.
   __ LeaveStubFrame();
   __ ret();
 }
 
@@ skipping 465 matching lines @@
 //   RSP : points to return address.
 //   RSP + 8 : address of last argument.
 //   R10 : arguments descriptor array.
 void StubCode::GenerateCallClosureNoSuchMethodStub(Assembler* assembler) {
   __ EnterStubFrame();
 
   // Load the receiver.
   __ movq(R13, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   __ movq(RAX, Address(RBP, R13, TIMES_4, kParamEndSlotFromFp * kWordSize));
 
-  __ LoadObject(R12, Object::null_object());
-  __ pushq(R12);  // Setup space on stack for result from noSuchMethod.
+  __ pushq(Immediate(0));  // Result slot.
   __ pushq(RAX);  // Receiver.
   __ pushq(R10);  // Arguments descriptor array.
 
   __ movq(R10, R13);  // 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.
   __ int3();
@@ skipping 210 matching lines @@
 
   const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
   __ addq(R13, Immediate(entry_size));  // Next entry.
   __ movq(R9, Address(R13, 0));  // Next class ID.
 
   __ Bind(&test);
   __ cmpq(R9, Immediate(Smi::RawValue(kIllegalCid)));  // Done?
   __ j(NOT_EQUAL, &loop, Assembler::kNearJump);
 
   __ Comment("IC miss");
-  __ LoadObject(R13, Object::null_object());
   // Compute address of arguments (first read number of arguments from
   // arguments descriptor array and then compute address on the stack).
   __ movq(RAX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   __ leaq(RAX, Address(RSP, RAX, TIMES_4, 0));  // RAX is Smi.
   __ EnterStubFrame();
   __ pushq(R10);  // Preserve arguments descriptor array.
   __ pushq(RBX);  // Preserve IC data object.
-  __ pushq(R13);  // Setup space on stack for result (target code object).
+  __ pushq(Immediate(0));  // Result slot.
   // Push call arguments.
   for (intptr_t i = 0; i < num_args; i++) {
     __ movq(RCX, Address(RAX, -kWordSize * i));
     __ pushq(RCX);
   }
   __ pushq(RBX);  // Pass IC data object.
   __ CallRuntime(handle_ic_miss, num_args + 1);
   // Remove the call arguments pushed earlier, including the IC data object.
   for (intptr_t i = 0; i < num_args + 1; i++) {
     __ popq(RAX);
@@ skipping 238 matching lines @@
   __ movq(CODE_REG, FieldAddress(RAX, Function::code_offset()));
   __ movq(RAX, FieldAddress(RAX, Function::entry_point_offset()));
   __ jmp(RAX);
 }
 
 
 // RBX: Contains an ICData.
 // TOS(0): return address (Dart code).
 void StubCode::GenerateICCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
-  // Preserve IC data.
-  __ pushq(RBX);
-  // Room for result. Debugger stub returns address of the
-  // unpatched runtime stub.
-  __ LoadObject(R12, Object::null_object());
-  __ pushq(R12);  // Room for result.
+  __ pushq(RBX);  // Preserve IC data.
+  __ pushq(Immediate(0));  // Result slot.
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
-  __ popq(CODE_REG);  // Address of original.
+  __ popq(CODE_REG);  // Original stub.
   __ popq(RBX);  // Restore IC data.
   __ LeaveStubFrame();
 
   __ movq(RAX, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ jmp(RAX);   // Jump to original stub.
 }
 
 
 //  TOS(0): return address (Dart code).
 void StubCode::GenerateRuntimeCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
-  // Room for result. Debugger stub returns address of the
-  // unpatched runtime stub.
-  __ LoadObject(R12, Object::null_object());
-  __ pushq(R12);  // Room for result.
+  __ pushq(Immediate(0));  // Result slot.
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
-  __ popq(CODE_REG);  // Address of original.
+  __ popq(CODE_REG);  // Original stub.
   __ LeaveStubFrame();
 
   __ movq(RAX, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ jmp(RAX);   // Jump to original stub.
 }
 
 
 // Called only from unoptimized code.
 void StubCode::GenerateDebugStepCheckStub(Assembler* assembler) {
   // Check single stepping.
@@ skipping 171 matching lines @@
           Immediate(0));
   __ jmp(CallingConventions::kArg1Reg);  // Jump to the exception handler code.
 }
 
 
 // Calls to the runtime to optimize the given function.
 // RDI: function to be reoptimized.
 // R10: argument descriptor (preserved).
 void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
   __ EnterStubFrame();
-  __ LoadObject(R12, Object::null_object());
-  __ pushq(R10);
-  __ pushq(R12);  // Setup space on stack for return value.
-  __ pushq(RDI);
+  __ pushq(R10);  // Preserve args descriptor.
+  __ pushq(Immediate(0));  // Result slot.
+  __ pushq(RDI);  // Arg0: function to optimize
   __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry, 1);
   __ popq(RAX);  // Disard argument.
   __ popq(CODE_REG);  // Get Code object.
   __ popq(R10);  // Restore argument descriptor.
   __ movq(RAX, FieldAddress(CODE_REG, Code::entry_point_offset()));
   __ LeaveStubFrame();
   __ jmp(RAX);
   __ int3();
 }
 
@@ skipping 268 matching lines @@
 
 
 //  RDI: receiver
 //  RBX: UnlinkedCall
 void StubCode::GenerateUnlinkedCallStub(Assembler* assembler) {
   __ NoMonomorphicCheckedEntry();
 
   __ EnterStubFrame();
   __ pushq(RDI);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ pushq(RDI);                         // Arg0: Receiver
-  __ pushq(RBX);                         // Arg1: UnlinkedCall
+  __ pushq(Immediate(0));  // Result slot.
+  __ pushq(RDI);           // Arg0: Receiver
+  __ pushq(RBX);           // Arg1: UnlinkedCall
   __ CallRuntime(kUnlinkedCallRuntimeEntry, 2);
   __ popq(RBX);
   __ popq(RBX);
   __ popq(RBX);  // result = IC
 
   __ popq(RDI);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ movq(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ movq(RCX, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
@@ skipping 18 matching lines @@
   __ cmpq(RAX, R10);
   __ j(GREATER, &miss, Assembler::kNearJump);
   __ movq(RCX, FieldAddress(RBX, SingleTargetCache::entry_point_offset()));
   __ movq(CODE_REG, FieldAddress(RBX, SingleTargetCache::target_offset()));
   __ jmp(RCX);
 
   __ Bind(&miss);
   __ EnterStubFrame();
   __ pushq(RDI);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ pushq(RDI);                         // Arg0: Receiver
+  __ pushq(Immediate(0));  // Result slot.
+  __ pushq(RDI);           // Arg0: Receiver
   __ CallRuntime(kSingleTargetMissRuntimeEntry, 1);
   __ popq(RBX);
   __ popq(RBX);  // result = IC
 
   __ popq(RDI);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ movq(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ movq(RCX, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ jmp(RCX);
 }
 
 
 // Called from the monomorphic checked entry.
 //  RDI: receiver
 void StubCode::GenerateMonomorphicMissStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ pushq(RDI);  // Preserve receiver.
 
-  __ PushObject(Object::null_object());  // Result.
-  __ pushq(RDI);                         // Arg0: Receiver
+  __ pushq(Immediate(0));  // Result slot.
+  __ pushq(RDI);           // Arg0: Receiver
   __ CallRuntime(kMonomorphicMissRuntimeEntry, 1);
   __ popq(RBX);
   __ popq(RBX);  // result = IC
 
   __ popq(RDI);  // Restore receiver.
   __ LeaveStubFrame();
 
   __ movq(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ movq(RCX, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ jmp(RCX);
 }
 
 
 void StubCode::GenerateFrameAwaitingMaterializationStub(Assembler* assembler) {
   __ int3();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64