V4: Add a lowering pass to the traced JIT

This pass converts high-level operations like e.g. a JSAdd to lower
level operations, like a runtime call. This pass will be extended to
take trace information, which can indicate that it can be lowered to
e.g. an AddInt32.

Change-Id: Ieae8df235217189c90048515e199f7e7c7f220b3
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

4 files changed, 315 insertions, 1 deletions

diff --git a/src/qml/jit/jit.pri b/src/qml/jit/jit.pri
index 49eb2e8a37..e8d5860498 100644
--- a/src/qml/jit/jit.pri
+++ b/src/qml/jit/jit.pri
@@ -18,7 +18,8 @@ SOURCES += \
     $$PWD/qv4node.cpp \
     $$PWD/qv4graph.cpp \
     $$PWD/qv4graphbuilder.cpp \
-    $$PWD/qv4tracingjit.cpp \
+    $$PWD/qv4lowering.cpp \
+    $$PWD/qv4tracingjit.cpp
 
 HEADERS += \
     $$PWD/qv4ir_p.h \
@@ -27,4 +28,5 @@ HEADERS += \
     $$PWD/qv4node_p.h \
     $$PWD/qv4graph_p.h \
     $$PWD/qv4graphbuilder_p.h \
+    $$PWD/qv4lowering_p.h
 }
diff --git a/src/qml/jit/qv4lowering.cpp b/src/qml/jit/qv4lowering.cpp
new file mode 100644
index 0000000000..3b3711e7fa
--- /dev/null
+++ b/src/qml/jit/qv4lowering.cpp
@@ -0,0 +1,200 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QLoggingCategory>
+
+#include "qv4lowering_p.h"
+#include "qv4graph_p.h"
+
+QT_REQUIRE_CONFIG(qml_tracing);
+
+QT_BEGIN_NAMESPACE
+namespace QV4 {
+namespace IR {
+
+Q_LOGGING_CATEGORY(lcLower, "qt.v4.ir.lowering")
+
+GenericLowering::GenericLowering(Function &f)
+    : m_function(f)
+{}
+
+void GenericLowering::lower()
+{
+    NodeWorkList worklist(graph());
+    // The order doesn't really matter for generic lowering, as long as it's done in 1 pass, and
+    // have any clean-up done afterwards.
+    worklist.enqueueAllInputs(graph()->endNode());
+
+    while (Node *n = worklist.dequeueNextNodeForVisiting()) {
+        worklist.enqueueAllInputs(n);
+
+        if (!CallPayload::isRuntimeCall(n->opcode()))
+            continue;
+
+        if (CallPayload::isVarArgsCall(n->opcode()))
+            replaceWithVarArgsCall(n);
+        else
+            replaceWithCall(n);
+    }
+}
+
+void GenericLowering::replaceWithCall(Node *n)
+{
+    auto newOp = opBuilder()->getCall(n->opcode());
+
+    QVarLengthArray<Node *, 32> args;
+    if (CallPayload::takesEngineAsArg(n->opcode(), 0))
+        args.append(graph()->engineNode());
+    if (CallPayload::takesFunctionAsArg(n->opcode(), args.size()))
+        args.append(graph()->functionNode());
+    if (CallPayload::takesFrameAsArg(n->opcode(), args.size()))
+        args.append(graph()->cppFrameNode());
+    const int extraLeadingArguments = args.size();
+
+    for (unsigned arg = 0, earg = n->inputCount(); arg != earg; ++arg) {
+        Node *input = n->input(arg);
+        if (input->opcode() == Meta::FrameState)
+            continue;
+
+        if (arg >= n->operation()->valueInputCount()) {
+            // effect or control input
+            args.append(input);
+            continue;
+        }
+
+        if (CallPayload::needsStorageOnJSStack(n->opcode(), args.size(), input->operation(),
+                                               function().nodeInfo(input)->type()))
+            input = graph()->createNode(opBuilder()->get<Meta::Alloca>(), input);
+
+        args.append(input);
+    }
+
+    Node *newCall = graph()->createNode(newOp, args.data(), args.size());
+
+    qCDebug(lcLower) << "replacing node" << n->id() << n->operation()->debugString()
+                     << "with node" << newCall->id() << newOp->debugString();
+    qCDebug(lcLower) << "... old node #inputs:" << n->inputCount();
+    qCDebug(lcLower) << "... old node #uses:" << n->useCount();
+
+    function().nodeInfo(newCall)->setType(CallPayload::returnType(n->opcode()));
+    n->replaceAllUsesWith(newCall);
+    n->kill();
+
+    qCDebug(lcLower) << "... new node #inputs:" << newCall->inputCount();
+    qCDebug(lcLower) << "... new node #uses:" << newCall->useCount();
+
+    for (Node *use : newCall->uses()) {
+        // fix-up indices for SelectOutput:
+        if (use->opcode() == Meta::SelectOutput) {
+            const int oldIndex = ConstantPayload::get(*use->input(1)->operation())->value().int_32();
+            const int newIndex = oldIndex + extraLeadingArguments;
+            use->replaceInput(1, graph()->createConstantIntNode(newIndex));
+            use->replaceInput(2, newCall->input(newIndex));
+            break;
+        }
+    }
+}
+
+void GenericLowering::replaceWithVarArgsCall(Node *n)
+{
+    const bool isTailCall = n->opcode() == Meta::JSTailCall;
+    Operation *newOp = isTailCall ? opBuilder()->getTailCall()
+                                  : opBuilder()->getCall(n->opcode());
+
+    //### optimize this for 0 and 1 argument: we don't need to create a VarArgs array for these cases
+
+    const unsigned varArgsStart = CallPayload::varArgsStart(n->opcode()) - 1; // subtract 1 because the runtime calls all take the engine argument as arg0, which isn't in the graph before lowering.
+    Node *vaAlloc = graph()->createNode(
+                opBuilder()->get<Meta::VAAlloc>(),
+                graph()->createConstantIntNode(n->operation()->valueInputCount() - varArgsStart),
+                n->effectInput());
+    QVarLengthArray<Node *, 32> vaSealIn;
+    vaSealIn.append(vaAlloc);
+    for (unsigned i = varArgsStart, ei = n->operation()->valueInputCount(); i != ei; ++i) {
+        vaSealIn.append(graph()->createNode(opBuilder()->get<Meta::VAStore>(), vaAlloc,
+                                            graph()->createConstantIntNode(vaSealIn.size() - 1),
+                                            n->input(i)));
+    }
+    vaSealIn.append(vaAlloc);
+    Node *vaSeal = graph()->createNode(opBuilder()->getVASeal(vaSealIn.size() - 2),
+                                 vaSealIn.data(),
+                                 vaSealIn.size());
+    QVarLengthArray<Node *, 8> callArgs;
+    if (isTailCall)
+        callArgs.append(graph()->cppFrameNode());
+    callArgs.append(graph()->engineNode());
+    for (unsigned i = 0; i != varArgsStart; ++i) {
+        Node *input = n->input(i);
+        if (CallPayload::needsStorageOnJSStack(n->opcode(), callArgs.size(), input->operation(),
+                                               function().nodeInfo(input)->type()))
+            input = graph()->createNode(opBuilder()->get<Meta::Alloca>(), input);
+        callArgs.append(input);
+    }
+    callArgs.append(vaSeal); // args
+    if (n->opcode() != Meta::JSCreateClass) // JSCreateClass is the odd duck
+        callArgs.append(graph()->createConstantIntNode(vaSealIn.size() - 2)); // argc
+    callArgs.append(vaSeal); // effect
+    callArgs.append(n->controlInput(0)); // control flow
+    Node *newCall = graph()->createNode(newOp, callArgs.data(), unsigned(callArgs.size()));
+
+    qCDebug(lcLower) << "replacing node" << n->id() << n->operation()->debugString()
+                     << "with node" << newCall->id() << newOp->debugString();
+    qCDebug(lcLower) << "... old node #inputs:" << n->inputCount();
+    qCDebug(lcLower) << "... old node #uses:" << n->useCount();
+
+    n->replaceAllUsesWith(newCall);
+    n->kill();
+
+    qCDebug(lcLower) << "... new node #inputs:" << newCall->inputCount();
+    qCDebug(lcLower) << "... new node #uses:" << newCall->useCount();
+}
+
+bool GenericLowering::allUsesAsUnboxedBool(Node *n)
+{
+    for (Node *use : n->uses()) {
+        if (use->operation()->kind() != Meta::Branch)
+            return false;
+    }
+
+    return true;
+}
+
+} // IR namespace
+} // QV4 namespace
+QT_END_NAMESPACE
diff --git a/src/qml/jit/qv4lowering_p.h b/src/qml/jit/qv4lowering_p.h
new file mode 100644
index 0000000000..0b482bc9f0
--- /dev/null
+++ b/src/qml/jit/qv4lowering_p.h
@@ -0,0 +1,107 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QV4LOWERING_P_H
+#define QV4LOWERING_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <private/qqmljsmemorypool_p.h>
+#include <private/qv4global_p.h>
+#include <private/qv4ir_p.h>
+#include <private/qv4util_p.h>
+#include <private/qv4node_p.h>
+#include <private/qv4graph_p.h>
+
+QT_REQUIRE_CONFIG(qml_tracing);
+
+QT_BEGIN_NAMESPACE
+
+namespace QV4 {
+namespace IR {
+
+// Lowering replaces JS level operations with lower level ones. E.g. a JSAdd is lowered to an AddI32
+// if both inputs and the output are 32bit integers, or to a runtime call in all other cases. This
+// transforms the graph into something that is closer to actual executable code.
+
+
+// Last lowering phase: replace all JSOperations that are left with runtime calls. There is nothing
+// smart here, all that should have been done before this phase.
+class GenericLowering final
+{
+    Q_DISABLE_COPY(GenericLowering)
+
+public:
+    GenericLowering(Function &f);
+
+    void lower();
+
+private:
+    void replaceWithCall(Node *n);
+    void replaceWithVarArgsCall(Node *n);
+    static bool allUsesAsUnboxedBool(Node *n);
+
+    Function &function()
+    { return m_function; }
+
+    Graph *graph()
+    { return function().graph(); }
+
+    OperationBuilder *opBuilder()
+    { return graph()->opBuilder(); }
+
+private:
+    Function &m_function;
+};
+
+} // namespace IR
+} // namespace QV4
+
+QT_END_NAMESPACE
+
+#endif // QV4LOWERING_P_H
diff --git a/src/qml/jit/qv4tracingjit.cpp b/src/qml/jit/qv4tracingjit.cpp
index ded2488905..889c0516d3 100644
--- a/src/qml/jit/qv4tracingjit.cpp
+++ b/src/qml/jit/qv4tracingjit.cpp
@@ -41,6 +41,7 @@
 
 #include "qv4vme_moth_p.h"
 #include "qv4graphbuilder_p.h"
+#include "qv4lowering_p.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -73,6 +74,10 @@ void Moth::runTracingJit(QV4::Function *function)
     IR::GraphBuilder::buildGraph(&irFunction);
     irFunction.dump(QStringLiteral("initial IR"));
     irFunction.verify();
+
+    IR::GenericLowering(irFunction).lower();
+    irFunction.dump(QStringLiteral("after generic lowering"));
+    irFunction.verify();
 }
 
 } // QV4 namespace