Refactor Call/Construct instructions

Give them a pointer to argc and argv instead of a pointer
to a full callData. Like this we can construct the callData
at the end of the JS stack and avoid the need to create an
additional copy in VME::exec().

This also opens up the option of completely avoiding all copies for
calls into runtime methods.

Also make sure that the calldata we pass into other functions is
always at the top of the JS stack.

Change-Id: I3d0eb49f7bfd7adb9ddabb213422087c66e5a520
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

1 files changed, 30 insertions, 25 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 706f211ae0..331132de3b 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -1256,42 +1256,49 @@ bool Codegen::visit(CallExpression *ast)
             Instruction::CallPropertyLookup call;
             call.base = base.propertyBase.stackSlot();
             call.lookupIndex = registerGetterLookup(base.propertyNameIndex);
-            call.callData = calldata;
+            call.argc = calldata.argc;
+            call.argv = calldata.argv;
             bytecodeGenerator->addInstruction(call);
         } else {
             Instruction::CallProperty call;
             call.base = base.propertyBase.stackSlot();
             call.name = base.propertyNameIndex;
-            call.callData = calldata;
+            call.argc = calldata.argc;
+            call.argv = calldata.argv;
             bytecodeGenerator->addInstruction(call);
         }
     } else if (base.type == Reference::Subscript) {
         Instruction::CallElement call;
         call.base = base.elementBase;
         call.index = base.elementSubscript.stackSlot();
-        call.callData = calldata;
+        call.argc = calldata.argc;
+        call.argv = calldata.argv;
         bytecodeGenerator->addInstruction(call);
     } else if (base.type == Reference::Name) {
         if (base.name == QStringLiteral("eval")) {
             Instruction::CallPossiblyDirectEval call;
-            call.callData = calldata;
+            call.argc = calldata.argc;
+            call.argv = calldata.argv;
             bytecodeGenerator->addInstruction(call);
         } else if (useFastLookups && base.global) {
             Instruction::CallGlobalLookup call;
             call.index = registerGlobalGetterLookup(base.nameAsIndex());
-            call.callData = calldata;
+            call.argc = calldata.argc;
+            call.argv = calldata.argv;
             bytecodeGenerator->addInstruction(call);
         } else {
             Instruction::CallName call;
             call.name = base.nameAsIndex();
-            call.callData = calldata;
+            call.argc = calldata.argc;
+            call.argv = calldata.argv;
             bytecodeGenerator->addInstruction(call);
         }
     } else {
         base.loadInAccumulator();
 
         Instruction::CallValue call;
-        call.callData = calldata;
+        call.argc = calldata.argc;
+        call.argv = calldata.argv;
         bytecodeGenerator->addInstruction(call);
     }
 
@@ -1299,21 +1306,16 @@ bool Codegen::visit(CallExpression *ast)
     return false;
 }
 
-Moth::StackSlot Codegen::pushArgs(ArgumentList *args)
+Codegen::Arguments Codegen::pushArgs(ArgumentList *args)
 {
     int argc = 0;
     for (ArgumentList *it = args; it; it = it->next)
         ++argc;
-    int calldata = bytecodeGenerator->newRegisterArray(sizeof(CallData)/sizeof(Value) - 1 + argc);
 
-#ifndef QT_NO_DEBUG
-    (void) Reference::fromConst(this, QV4::Encode::undefined()).storeOnStack(calldata + CallData::Function);
-    (void) Reference::fromConst(this, QV4::Encode::undefined()).storeOnStack(calldata + CallData::Context);
-    (void) Reference::fromConst(this, QV4::Encode::undefined()).storeOnStack(calldata + CallData::Accumulator);
-    (void) Reference::fromConst(this, QV4::Encode::undefined()).storeOnStack(calldata + CallData::This);
-#endif
-    (void) Reference::fromConst(this, QV4::Encode(argc)).storeOnStack(calldata + CallData::Argc);
-    Q_STATIC_ASSERT(sizeof(CallData) == 6 * sizeof(Value));
+    if (!argc)
+        return { 0, 0 };
+
+    int calldata = bytecodeGenerator->newRegisterArray(argc);
 
     argc = 0;
     for (ArgumentList *it = args; it; it = it->next) {
@@ -1321,11 +1323,16 @@ Moth::StackSlot Codegen::pushArgs(ArgumentList *args)
         Reference e = expression(it->expression);
         if (hasError)
             break;
-        (void) e.storeOnStack(calldata + sizeof(CallData)/sizeof(Value) - 1 + argc);
+        if (!argc && !it->next) {
+            // avoid copy for functions taking a single argument
+            if (e.isStackSlot())
+                return { 1, e.stackSlot() };
+        }
+        (void) e.storeOnStack(calldata + argc);
         ++argc;
     }
 
-    return Moth::StackSlot::createRegister(calldata);
+    return { argc, calldata };
 }
 
 bool Codegen::visit(ConditionalExpression *ast)
@@ -1581,11 +1588,10 @@ bool Codegen::visit(NewExpression *ast)
     //### Maybe create a ConstructA that takes an accumulator?
     base = base.storeOnStack();
 
-    auto calldata = pushArgs(0);
-
     Instruction::Construct create;
     create.func = base.stackSlot();
-    create.callData = calldata;
+    create.argc = 0;
+    create.argv = 0;
     bytecodeGenerator->addInstruction(create);
     _expr.setResult(Reference::fromAccumulator(this));
     return false;
@@ -1609,7 +1615,8 @@ bool Codegen::visit(NewMemberExpression *ast)
 
     Instruction::Construct create;
     create.func = base.stackSlot();
-    create.callData = calldata;
+    create.argc = calldata.argc;
+    create.argv = calldata.argv;
     bytecodeGenerator->addInstruction(create);
     _expr.setResult(Reference::fromAccumulator(this));
     return false;
@@ -2024,8 +2031,6 @@ int Codegen::defineFunction(const QString &name, AST::Node *ast,
     _context->functionIndex = _module->functions.count() - 1;
 
     _context->hasDirectEval |= (_context->compilationMode == EvalCode || _context->compilationMode == GlobalCode || _module->debugMode); // Conditional breakpoints are like eval in the function
-    // ### still needed?
-    _context->maxNumberOfArguments = qMax(_context->maxNumberOfArguments, (int)QV4::Global::ReservedArgumentCount);
 
     BytecodeGenerator bytecode(_context->line, _module->debugMode);
     BytecodeGenerator *savedBytecodeGenerator;