Refactor InteratorNext instruction

The instruction now writes the value into a stack slot,
and returns the done state in the accumulator. This should
make it easier to implement the IteratorClose functionality
required by the spec.

Change-Id: I8cc497c54b0d044bd3c68a5a1b774eea8b2740ef
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

8 files changed, 26 insertions, 21 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index f00a0fafdc..99c45d19fa 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -477,6 +477,7 @@ void Codegen::destructureElementList(const Codegen::Reference &array, PatternEle
     RegisterScope scope(this);
 
     Reference iterator = Reference::fromStackSlot(this);
+    Reference iteratorValue = Reference::fromStackSlot(this);
 
     array.loadInAccumulator();
     Instruction::GetIterator iteratorObjInstr;
@@ -490,7 +491,7 @@ void Codegen::destructureElementList(const Codegen::Reference &array, PatternEle
         for (Elision *elision = p->elision; elision; elision = elision->next) {
             iterator.loadInAccumulator();
             Instruction::IteratorNext next;
-            next.returnUndefinedWhenDone = true;
+            next.value = iteratorValue.stackSlot();
             bytecodeGenerator->addInstruction(next);
         }
 
@@ -503,12 +504,12 @@ void Codegen::destructureElementList(const Codegen::Reference &array, PatternEle
             initializeAndDestructureBindingElement(e, Reference::fromAccumulator(this));
         } else {
             Instruction::IteratorNext next;
-            next.returnUndefinedWhenDone = true;
+            next.value = iteratorValue.stackSlot();
             bytecodeGenerator->addInstruction(next);
             if (!e)
                 continue;
             if (e->type != PatternElement::RestElement) {
-                initializeAndDestructureBindingElement(e, Reference::fromAccumulator(this));
+                initializeAndDestructureBindingElement(e, iteratorValue);
                 if (hasError) {
                     end.link();
                     return;
@@ -2686,11 +2687,9 @@ bool Codegen::visit(ForEachStatement *ast)
     in.link();
     iterator.loadInAccumulator();
     Instruction::IteratorNext next;
-    next.returnUndefinedWhenDone = false;
+    next.value = lhsValue.stackSlot();
     bytecodeGenerator->addInstruction(next);
-    Instruction::JumpEmpty jump;
-    BytecodeGenerator::Jump done = bytecodeGenerator->addJumpInstruction(jump);
-    lhsValue.storeConsumeAccumulator();
+    BytecodeGenerator::Jump done = bytecodeGenerator->addJumpInstruction(Instruction::JumpTrue());
     bytecodeGenerator->jump().link(body);
 
     done.link();
diff --git a/src/qml/compiler/qv4instr_moth.cpp b/src/qml/compiler/qv4instr_moth.cpp
index 8c5dfefdf1..7d8a1774f1 100644
--- a/src/qml/compiler/qv4instr_moth.cpp
+++ b/src/qml/compiler/qv4instr_moth.cpp
@@ -434,7 +434,7 @@ void dumpBytecode(const char *code, int len, int nLocals, int nFormals, int /*st
         MOTH_END_INSTR(GetIterator)
 
         MOTH_BEGIN_INSTR(IteratorNext)
-            d << returnUndefinedWhenDone;
+            d << value;
         MOTH_END_INSTR(IteratorNext)
 
         MOTH_BEGIN_INSTR(DestructureRestElement)
diff --git a/src/qml/compiler/qv4instr_moth_p.h b/src/qml/compiler/qv4instr_moth_p.h
index 670d977a57..b4eaae4f6c 100644
--- a/src/qml/compiler/qv4instr_moth_p.h
+++ b/src/qml/compiler/qv4instr_moth_p.h
@@ -122,7 +122,7 @@ QT_BEGIN_NAMESPACE
 #define INSTR_PopScriptContext(op) INSTRUCTION(op, PopScriptContext, 0)
 #define INSTR_PopContext(op) INSTRUCTION(op, PopContext, 1, reg)
 #define INSTR_GetIterator(op) INSTRUCTION(op, GetIterator, 1, iterator)
-#define INSTR_IteratorNext(op) INSTRUCTION(op, IteratorNext, 1, returnUndefinedWhenDone)
+#define INSTR_IteratorNext(op) INSTRUCTION(op, IteratorNext, 1, value)
 #define INSTR_DestructureRestElement(op) INSTRUCTION(op, DestructureRestElement, 0)
 #define INSTR_DeleteMember(op) INSTRUCTION(op, DeleteMember, 2, member, base)
 #define INSTR_DeleteSubscript(op) INSTRUCTION(op, DeleteSubscript, 2, base, index)
diff --git a/src/qml/jit/qv4jit.cpp b/src/qml/jit/qv4jit.cpp
index ff139e6645..a480cfbc30 100644
--- a/src/qml/jit/qv4jit.cpp
+++ b/src/qml/jit/qv4jit.cpp
@@ -714,11 +714,11 @@ void BaselineJIT::generate_GetIterator(int iterator)
     as->checkException();
 }
 
-void BaselineJIT::generate_IteratorNext(int returnUndefinedWhenDone)
+void BaselineJIT::generate_IteratorNext(int value)
 {
     as->saveAccumulatorInFrame();
     as->prepareCallWithArgCount(3);
-    as->passInt32AsArg(returnUndefinedWhenDone, 2);
+    as->passRegAsArg(value, 2);
     as->passAccumulatorAsArg(1);
     as->passEngineAsArg(0);
     JIT_GENERATE_RUNTIME_CALL(Runtime::method_iteratorNext, Assembler::ResultInAccumulator);
diff --git a/src/qml/jit/qv4jit_p.h b/src/qml/jit/qv4jit_p.h
index d57e043bc2..fa4a367e91 100644
--- a/src/qml/jit/qv4jit_p.h
+++ b/src/qml/jit/qv4jit_p.h
@@ -186,7 +186,7 @@ public:
     void generate_PopScriptContext() override;
     void generate_PopContext(int reg) override;
     void generate_GetIterator(int iterator) override;
-    void generate_IteratorNext(int returnUndefinedWhenDone) override;
+    void generate_IteratorNext(int value) override;
     void generate_DestructureRestElement() override;
     void generate_DeleteMember(int member, int base) override;
     void generate_DeleteSubscript(int base, int index) override;
diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 2c00826b46..650f5c6735 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -715,7 +715,7 @@ ReturnedValue Runtime::method_getIterator(ExecutionEngine *engine, const Value &
     return engine->newForInIteratorObject(o)->asReturnedValue();
 }
 
-ReturnedValue Runtime::method_iteratorNext(ExecutionEngine *engine, const Value &iterator, int returnUndefinedWhenDone)
+ReturnedValue Runtime::method_iteratorNext(ExecutionEngine *engine, const Value &iterator, Value *value)
 {
     Q_ASSERT(iterator.isObject());
 
@@ -727,10 +727,14 @@ ReturnedValue Runtime::method_iteratorNext(ExecutionEngine *engine, const Value
     ScopedObject o(scope, f->call(cData));
     if (!o)
         return engine->throwTypeError();
-    ScopedValue v(scope, o->get(engine->id_done()));
-    if (v->toBoolean() == true)
-        return returnUndefinedWhenDone ? Encode::undefined() : Primitive::emptyValue().asReturnedValue();
-    return o->get(engine->id_value());
+    ScopedValue d(scope, o->get(engine->id_done()));
+    bool done = d->toBoolean();
+    if (done) {
+        *value = Encode::undefined();
+    } else {
+        *value = o->get(engine->id_value());
+    }
+    return Encode(done);
 }
 
 ReturnedValue Runtime::method_destructureRestElement(ExecutionEngine *engine, const Value &iterator)
@@ -742,10 +746,12 @@ ReturnedValue Runtime::method_destructureRestElement(ExecutionEngine *engine, co
     array->arrayCreate();
     uint index = 0;
     while (1) {
-        ScopedValue n(scope, method_iteratorNext(engine, iterator, false));
+        ScopedValue n(scope);
+        ScopedValue done(scope, method_iteratorNext(engine, iterator, n));
         if (engine->hasException)
             return Encode::undefined();
-        if (n->isEmpty())
+        Q_ASSERT(done->isBoolean());
+        if (done->booleanValue())
             break;
         array->arraySet(index, n);
         ++index;
diff --git a/src/qml/jsruntime/qv4runtimeapi_p.h b/src/qml/jsruntime/qv4runtimeapi_p.h
index 0d27fbfe7b..a22a053cd1 100644
--- a/src/qml/jsruntime/qv4runtimeapi_p.h
+++ b/src/qml/jsruntime/qv4runtimeapi_p.h
@@ -146,7 +146,7 @@ struct ExceptionCheck<void (*)(QV4::NoThrowEngine *, A, B, C)> {
     \
     /* for-in, for-of and array destructuring */ \
     F(ReturnedValue, getIterator, (ExecutionEngine *engine, const Value &in, int iterator)) \
-    F(ReturnedValue, iteratorNext, (ExecutionEngine *engine, const Value &iterator, int returnUndefinedWhenDone)) \
+    F(ReturnedValue, iteratorNext, (ExecutionEngine *engine, const Value &iterator, Value *value)) \
     F(ReturnedValue, destructureRestElement, (ExecutionEngine *engine, const Value &iterator)) \
     \
     /* unary operators */ \
diff --git a/src/qml/jsruntime/qv4vme_moth.cpp b/src/qml/jsruntime/qv4vme_moth.cpp
index 8b45226fcd..17ed1ae044 100644
--- a/src/qml/jsruntime/qv4vme_moth.cpp
+++ b/src/qml/jsruntime/qv4vme_moth.cpp
@@ -961,7 +961,7 @@ QV4::ReturnedValue VME::interpret(CppStackFrame &frame, const uchar *code)
 
     MOTH_BEGIN_INSTR(IteratorNext)
         STORE_ACC();
-        acc = Runtime::method_iteratorNext(engine, accumulator, returnUndefinedWhenDone);
+        acc = Runtime::method_iteratorNext(engine, accumulator, &STACK_VALUE(value));
         CHECK_EXCEPTION;
     MOTH_END_INSTR(IteratorNext)