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Diffstat (limited to 'src/qml/jit/qv4loopinfo_p.h')
| -rw-r--r-- | src/qml/jit/qv4loopinfo_p.h | 159 |
1 files changed, 0 insertions, 159 deletions
diff --git a/src/qml/jit/qv4loopinfo_p.h b/src/qml/jit/qv4loopinfo_p.h deleted file mode 100644 index 6a865e6dc6..0000000000 --- a/src/qml/jit/qv4loopinfo_p.h +++ /dev/null @@ -1,159 +0,0 @@ -/**************************************************************************** -** -** 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 QV4LOOPINFO_P_H -#define QV4LOOPINFO_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 "qv4mi_p.h" - -#include <QHash> - -QT_REQUIRE_CONFIG(qml_tracing); - -QT_BEGIN_NAMESPACE - -namespace QV4 { -namespace IR { - -class DominatorTree; - -// Detect all (sub-)loops in a function. -// -// Doing loop detection on the CFG is better than relying on the statement information in -// order to mark loops. Although JavaScript only has natural loops, it can still be the case -// that something is not a loop even though a loop-like-statement is in the source. For -// example: -// while (true) { -// if (i > 0) -// break; -// else -// break; -// } -// -// Algorithm: -// - do a DFS on the dominator tree, where for each node: -// - collect all back-edges -// - if there are back-edges, the node is a loop-header for a new loop, so: -// - walk the CFG is reverse-direction, and for every node: -// - if the node already belongs to a loop, we've found a nested loop: -// - get the loop-header for the (outermost) nested loop -// - add that loop-header to the current loop -// - continue by walking all incoming edges that do not yet belong to the current loop -// - if the node does not belong to a loop yet, add it to the current loop, and -// go on with all incoming edges -// -// Loop-header detection by checking for back-edges is very straight forward: a back-edge is -// an incoming edge where the other node is dominated by the current node. Meaning: all -// execution paths that reach that other node have to go through the current node, that other -// node ends with a (conditional) jump back to the loop header. -// -// The exact order of the DFS on the dominator tree is not important. The only property has to -// be that a node is only visited when all the nodes it dominates have been visited before. -// The reason for the DFS is that for nested loops, the inner loop's loop-header is dominated -// by the outer loop's header. So, by visiting depth-first, sub-loops are identified before -// their containing loops, which makes nested-loop identification free. An added benefit is -// that the nodes for those sub-loops are only processed once. -// -// Note: independent loops that share the same header are merged together. For example, in -// the code snippet below, there are 2 back-edges into the loop-header, but only one single -// loop will be detected. -// while (a) { -// if (b) -// continue; -// else -// continue; -// } -class LoopInfo -{ - Q_DISABLE_COPY_MOVE(LoopInfo) - - struct BlockInfo - { - MIBlock *loopHeader = nullptr; - bool isLoopHeader = false; - std::vector<MIBlock *> loopExits; - }; - -public: - LoopInfo(const DominatorTree &dt) - : dt(dt) - {} - - ~LoopInfo() = default; - - void detectLoops(); - - MIBlock *loopHeaderFor(MIBlock *bodyBlock) const - { return blockInfos[bodyBlock->index()].loopHeader; } - - bool isLoopHeader(MIBlock *block) const - { return blockInfos[block->index()].isLoopHeader; } - - const std::vector<MIBlock *> loopExitsForLoop(MIBlock *loopHeader) const - { return blockInfos[loopHeader->index()].loopExits; } - -private: - void subLoop(MIBlock *loopHead, const std::vector<MIBlock *> &backedges); - void collectLoopExits(); - bool inLoopOrSubLoop(MIBlock *block, MIBlock *loopHeader) const; - - void dump() const; - -private: - const DominatorTree &dt; - std::vector<BlockInfo> blockInfos; -}; - -} // namespace IR -} // namespace QV4 - -QT_END_NAMESPACE - -#endif // QV4LOOPINFO_P_H |