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

runtime/vm/stub_code_ia32.cc

Index: runtime/vm/stub_code_ia32.cc
diff --git a/runtime/vm/stub_code_ia32.cc b/runtime/vm/stub_code_ia32.cc
index ee29ed5b72ec22df940b6a154101c5f688826387..cb805c6d96ac5703cab49b76c6e101fcbc211232 100644
--- a/runtime/vm/stub_code_ia32.cc
+++ b/runtime/vm/stub_code_ia32.cc
@@ -248,11 +248,9 @@ void StubCode::GenerateCallBootstrapCFunctionStub(Assembler* assembler) {
 // Input parameters:
 //   EDX: arguments descriptor array.
 void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   __ EnterStubFrame();
   __ pushl(EDX);  // Preserve arguments descriptor array.
-  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(Immediate(0));  // Setup space on stack for return value.
   __ CallRuntime(kPatchStaticCallRuntimeEntry, 0);
   __ popl(EAX);  // Get Code object result.
   __ popl(EDX);  // Restore arguments descriptor array.
@@ -268,13 +266,11 @@ void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
 // (invalid because its function was optimized or deoptimized).
 // EDX: arguments descriptor array.
 void StubCode::GenerateFixCallersTargetStub(Assembler* assembler) {
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
   __ pushl(EDX);  // Preserve arguments descriptor array.
-  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(Immediate(0));  // Setup space on stack for return value.
   __ CallRuntime(kFixCallersTargetRuntimeEntry, 0);
   __ popl(EAX);  // Get Code object.
   __ popl(EDX);  // Restore arguments descriptor array.
@@ -288,10 +284,8 @@ void StubCode::GenerateFixCallersTargetStub(Assembler* assembler) {
 // Called from object allocate instruction when the allocation stub has been
 // disabled.
 void StubCode::GenerateFixAllocationStubTargetStub(Assembler* assembler) {
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   __ EnterStubFrame();
-  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(Immediate(0));  // Setup space on stack for return value.
   __ CallRuntime(kFixAllocationStubTargetRuntimeEntry, 0);
   __ popl(EAX);  // Get Code object.
   __ movl(EAX, FieldAddress(EAX, Code::entry_point_offset()));
@@ -476,7 +470,7 @@ static void GenerateDispatcherCode(Assembler* assembler,
   __ movl(EDI, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   __ movl(EAX, Address(
       EBP, EDI, TIMES_HALF_WORD_SIZE, kParamEndSlotFromFp * kWordSize));
-  __ pushl(raw_null);  // Setup space on stack for result.
+  __ pushl(Immediate(0));  // Setup space on stack for result.
   __ pushl(EAX);  // Receiver.
   __ pushl(ECX);  // ICData/MegamorphicCache.
   __ pushl(EDX);  // Arguments descriptor array.
@@ -504,9 +498,7 @@ void StubCode::GenerateMegamorphicMissStub(Assembler* assembler) {
   __ pushl(ECX);
   __ pushl(EDX);
 
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Instructions::null()));
-  __ pushl(raw_null);  // Space for the result of the runtime call.
+  __ pushl(Immediate(0));  // Space for the result of the runtime call.
   __ pushl(EAX);  // Pass receiver.
   __ pushl(ECX);  // Pass IC data.
   __ pushl(EDX);  // Pass arguments descriptor.
@@ -539,8 +531,6 @@ void StubCode::GenerateMegamorphicMissStub(Assembler* assembler) {
 // The newly allocated object is returned in EAX.
 void StubCode::GenerateAllocateArrayStub(Assembler* assembler) {
   Label slow_case;
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   // Compute the size to be allocated, it is based on the array length
   // and is computed as:
   // RoundedAllocationSize((array_length * kwordSize) + sizeof(RawArray)).
@@ -661,7 +651,7 @@ void StubCode::GenerateAllocateArrayStub(Assembler* assembler) {
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
-  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(Immediate(0));  // Setup space on stack for return value.
   __ pushl(EDX);  // Array length as Smi.
   __ pushl(ECX);  // Element type.
   __ CallRuntime(kAllocateArrayRuntimeEntry, 2);
@@ -789,8 +779,6 @@ void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
 // EAX: new allocated RawContext object.
 // EBX and EDX are destroyed.
 void StubCode::GenerateAllocateContextStub(Assembler* assembler) {
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   if (FLAG_inline_alloc) {
     Label slow_case;
     // First compute the rounded instance size.
@@ -905,7 +893,7 @@ void StubCode::GenerateAllocateContextStub(Assembler* assembler) {
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
-  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(Immediate(0));  // Setup space on stack for return value.
   __ SmiTag(EDX);
   __ pushl(EDX);
   __ CallRuntime(kAllocateContextRuntimeEntry, 1);  // Allocate context.
@@ -1133,9 +1121,7 @@ void StubCode::GenerateCallClosureNoSuchMethodStub(Assembler* assembler) {
   __ movl(EDI, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   __ movl(EAX, Address(EBP, EDI, TIMES_2, kParamEndSlotFromFp * kWordSize));
 
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  __ pushl(raw_null);  // Setup space on stack for result from noSuchMethod.
+  __ pushl(Immediate(0));  // Setup space on stack for result from noSuchMethod.
   __ pushl(EAX);  // Receiver.
   __ pushl(EDX);  // Arguments descriptor array.
 
@@ -1368,8 +1354,6 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
   __ j(NOT_EQUAL, &loop, Assembler::kNearJump);
 
   __ Comment("IC miss");
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   // Compute address of arguments (first read number of arguments from
   // arguments descriptor array and then compute address on the stack).
   __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
@@ -1379,7 +1363,7 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
   __ EnterStubFrame();
   __ pushl(EDX);  // Preserve arguments descriptor array.
   __ pushl(ECX);  // Preserve IC data object.
-  __ pushl(raw_null);  // Setup space on stack for result (target code object).
+  __ pushl(Immediate(0));  // Result slot.
   // Push call arguments.
   for (intptr_t i = 0; i < num_args; i++) {
     __ movl(EBX, Address(EAX, -kWordSize * i));
@@ -1624,9 +1608,7 @@ void StubCode::GenerateICCallBreakpointStub(Assembler* assembler) {
   __ pushl(ECX);
   // Room for result. Debugger stub returns address of the
   // unpatched runtime stub.
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  __ pushl(raw_null);  // Room for result.
+  __ pushl(Immediate(0));  // Room for result.
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
   __ popl(EAX);  // Code of original stub.
   __ popl(ECX);  // Restore IC data.
@@ -1641,9 +1623,7 @@ void StubCode::GenerateRuntimeCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
   // Room for result. Debugger stub returns address of the
   // unpatched runtime stub.
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  __ pushl(raw_null);  // Room for result.
+  __ pushl(Immediate(0));  // Room for result.
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
   __ popl(EAX);  // Code of the original stub
   __ LeaveFrame();
@@ -1827,11 +1807,9 @@ void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
 // EBX: function to be reoptimized.
 // EDX: argument descriptor (preserved).
 void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
   __ EnterStubFrame();
   __ pushl(EDX);
-  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(Immediate(0));  // Setup space on stack for return value.
   __ pushl(EBX);
   __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry, 1);
   __ popl(EAX);  // Discard argument.