Cleanup code that modifies the JS stack

Change-Id: Ic043e256c3df984bb06c9a16b86573b0173b19a1
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

5 files changed, 35 insertions, 31 deletions

diff --git a/src/qml/jit/qv4isel_masm.cpp b/src/qml/jit/qv4isel_masm.cpp
index e7771f53d2..3894cea0a1 100644
--- a/src/qml/jit/qv4isel_masm.cpp
+++ b/src/qml/jit/qv4isel_masm.cpp
@@ -245,9 +245,30 @@ void InstructionSelection::run(int functionIndex)
 #endif
 
     const int locals = _as->stackLayout().calculateJSStackFrameSize();
-    _as->loadPtr(Address(Assembler::EngineRegister, qOffsetOf(ExecutionEngine, jsStackTop)), Assembler::LocalsRegister);
-    _as->addPtr(Assembler::TrustedImm32(sizeof(QV4::Value)*locals), Assembler::LocalsRegister);
-    _as->storePtr(Assembler::LocalsRegister, Address(Assembler::EngineRegister, qOffsetOf(ExecutionEngine, jsStackTop)));
+    if (locals > 0) {
+        _as->loadPtr(Address(Assembler::EngineRegister, qOffsetOf(ExecutionEngine, jsStackTop)), Assembler::LocalsRegister);
+#ifdef VALUE_FITS_IN_REGISTER
+        _as->move(Assembler::TrustedImm64(0), Assembler::ReturnValueRegister);
+        _as->move(Assembler::TrustedImm32(locals), Assembler::ScratchRegister);
+        Assembler::Label loop = _as->label();
+        _as->store64(Assembler::ReturnValueRegister, Assembler::Address(Assembler::LocalsRegister));
+        _as->add64(Assembler::TrustedImm32(8), Assembler::LocalsRegister);
+        Assembler::Jump jump = _as->branchSub32(Assembler::NonZero, Assembler::TrustedImm32(1), Assembler::ScratchRegister);
+        jump.linkTo(loop, _as);
+#else
+        _as->move(Assembler::TrustedImm32(0), Assembler::ReturnValueRegister);
+        _as->move(Assembler::TrustedImm32(locals), Assembler::ScratchRegister);
+        Assembler::Label loop = _as->label();
+        _as->store32(Assembler::ReturnValueRegister, Assembler::Address(Assembler::LocalsRegister));
+        _as->add32(Assembler::TrustedImm32(4), Assembler::LocalsRegister);
+        _as->store32(Assembler::ReturnValueRegister, Assembler::Address(Assembler::LocalsRegister));
+        _as->add32(Assembler::TrustedImm32(4), Assembler::LocalsRegister);
+        Assembler::Jump jump = _as->branchSub32(Assembler::NonZero, Assembler::TrustedImm32(1), Assembler::ScratchRegister);
+        jump.linkTo(loop, _as);
+#endif
+        _as->storePtr(Assembler::LocalsRegister, Address(Assembler::EngineRegister, qOffsetOf(ExecutionEngine, jsStackTop)));
+    }
+
 
     int lastLine = 0;
     for (int i = 0, ei = _function->basicBlockCount(); i != ei; ++i) {
diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index a7d26f8700..813b5fce5b 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -96,15 +96,6 @@ public:
     WTF::PageAllocation *jsStack;
     Value *jsStackBase;
 
-    Value *stackPush(uint nValues) {
-        Value *ptr = jsStackTop;
-        jsStackTop = ptr + nValues;
-        return ptr;
-    }
-    void stackPop(uint nValues) {
-        jsStackTop -= nValues;
-    }
-
     void pushForGC(Heap::Base *m) {
         *jsStackTop = m;
         ++jsStackTop;
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index 6a0496d1c5..437de33b3f 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -492,7 +492,7 @@ ReturnedValue SimpleScriptFunction::construct(Managed *that, CallData *callData)
     ctx.compilationUnit = f->function()->compilationUnit;
     ctx.lookups = ctx.compilationUnit->runtimeLookups;
     ctx.outer = f->scope();
-    ctx.locals = v4->stackPush(f->varCount());
+    ctx.locals = scope.alloc(f->varCount());
     while (callData->argc < (int)f->formalParameterCount()) {
         callData->args[callData->argc] = Encode::undefined();
         ++callData->argc;
@@ -529,7 +529,7 @@ ReturnedValue SimpleScriptFunction::call(Managed *that, CallData *callData)
     ctx.compilationUnit = f->function()->compilationUnit;
     ctx.lookups = ctx.compilationUnit->runtimeLookups;
     ctx.outer = f->scope();
-    ctx.locals = v4->stackPush(f->varCount());
+    ctx.locals = scope.alloc(f->varCount());
     while (callData->argc < (int)f->formalParameterCount()) {
         callData->args[callData->argc] = Encode::undefined();
         ++callData->argc;
diff --git a/src/qml/jsruntime/qv4scopedvalue_p.h b/src/qml/jsruntime/qv4scopedvalue_p.h
index 461d499694..6805fc80be 100644
--- a/src/qml/jsruntime/qv4scopedvalue_p.h
+++ b/src/qml/jsruntime/qv4scopedvalue_p.h
@@ -82,11 +82,12 @@ struct Scope {
     }
 
     Value *alloc(int nValues) {
-        Value *ptr = engine->jsStackTop;
-        engine->jsStackTop += nValues;
 #ifndef QT_NO_DEBUG
         size += nValues;
 #endif
+        Value *ptr = engine->jsStackTop;
+        engine->jsStackTop = ptr + nValues;
+        memset(ptr, 0, nValues*sizeof(Value));
         return ptr;
     }
 
@@ -111,6 +112,7 @@ struct ScopedValue
     ScopedValue(const Scope &scope)
     {
         ptr = scope.engine->jsStackTop++;
+        ptr->val = 0;
 #ifndef QT_NO_DEBUG
         ++scope.size;
 #endif
@@ -372,14 +374,9 @@ struct ScopedCallData {
     ScopedCallData(Scope &scope, int argc = 0)
     {
         int size = qMax(argc, (int)QV4::Global::ReservedArgumentCount) + qOffsetOf(QV4::CallData, args)/sizeof(QV4::Value);
-        ptr = reinterpret_cast<CallData *>(scope.engine->stackPush(size));
+        ptr = reinterpret_cast<CallData *>(scope.alloc(size));
         ptr->tag = QV4::Value::Integer_Type;
         ptr->argc = argc;
-#ifndef QT_NO_DEBUG
-        scope.size += size;
-        for (int ii = 0; ii < qMax(argc, (int)QV4::Global::ReservedArgumentCount); ++ii)
-            ptr->args[ii] = QV4::Primitive::undefinedValue();
-#endif
     }
 
     CallData *operator->() {
diff --git a/src/qml/jsruntime/qv4vme_moth.cpp b/src/qml/jsruntime/qv4vme_moth.cpp
index 8372aaa510..eb5fd1bcd8 100644
--- a/src/qml/jsruntime/qv4vme_moth.cpp
+++ b/src/qml/jsruntime/qv4vme_moth.cpp
@@ -143,7 +143,8 @@ QV4::ReturnedValue VME::run(ExecutionEngine *engine, const uchar *code
 
     const uchar *exceptionHandler = 0;
 
-    QV4::ExecutionContext *context = engine->currentContext();
+    QV4::Scope scope(engine);
+    QV4::ScopedContext context(scope, engine->currentContext());
     context->d()->lineNumber = -1;
 
 #ifdef DO_TRACE_INSTR
@@ -292,10 +293,7 @@ QV4::ReturnedValue VME::run(ExecutionEngine *engine, const uchar *code
     MOTH_BEGIN_INSTR(Push)
         TRACE(inline, "stack size: %u", instr.value);
         stackSize = instr.value;
-        stack = context->engine()->stackPush(stackSize);
-#ifndef QT_NO_DEBUG
-        memset(stack, 0, stackSize * sizeof(QV4::Value));
-#endif
+        stack = scope.alloc(stackSize);
         scopes[1] = stack;
     MOTH_END_INSTR(Push)
 
@@ -613,7 +611,6 @@ QV4::ReturnedValue VME::run(ExecutionEngine *engine, const uchar *code
     MOTH_END_INSTR(BinopContext)
 
     MOTH_BEGIN_INSTR(Ret)
-        context->engine()->stackPop(stackSize);
 //        TRACE(Ret, "returning value %s", result.toString(context)->toQString().toUtf8().constData());
         return VALUE(instr.result).asReturnedValue();
     MOTH_END_INSTR(Ret)
@@ -665,10 +662,8 @@ QV4::ReturnedValue VME::run(ExecutionEngine *engine, const uchar *code
         Q_ASSERT(false);
     catchException:
         Q_ASSERT(context->engine()->hasException);
-        if (!exceptionHandler) {
-            context->engine()->stackPop(stackSize);
+        if (!exceptionHandler)
             return QV4::Encode::undefined();
-        }
         code = exceptionHandler;
     }