| /* |
| * Copyright (C) 2012 Apple Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY |
| * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #include "config.h" |
| #include "DFGConstantFoldingPhase.h" |
| |
| #if ENABLE(DFG_JIT) |
| |
| #include "DFGAbstractState.h" |
| #include "DFGBasicBlock.h" |
| #include "DFGGraph.h" |
| #include "DFGInsertionSet.h" |
| #include "DFGPhase.h" |
| |
| namespace JSC { namespace DFG { |
| |
| class ConstantFoldingPhase : public Phase { |
| public: |
| ConstantFoldingPhase(Graph& graph) |
| : Phase(graph, "constant folding") |
| , m_state(graph) |
| { |
| } |
| |
| bool run() |
| { |
| bool changed = false; |
| |
| for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) { |
| BasicBlock* block = m_graph.m_blocks[blockIndex].get(); |
| if (!block) |
| continue; |
| if (!block->cfaDidFinish) |
| changed |= paintUnreachableCode(blockIndex); |
| if (block->cfaFoundConstants) |
| changed |= foldConstants(blockIndex); |
| } |
| |
| return changed; |
| } |
| |
| private: |
| bool foldConstants(BlockIndex blockIndex) |
| { |
| #if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE) |
| dataLog("Constant folding considering Block #%u.\n", blockIndex); |
| #endif |
| BasicBlock* block = m_graph.m_blocks[blockIndex].get(); |
| bool changed = false; |
| m_state.beginBasicBlock(block); |
| for (unsigned indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) { |
| NodeIndex nodeIndex = block->at(indexInBlock); |
| Node& node = m_graph[nodeIndex]; |
| |
| if (!m_state.isValid()) |
| break; |
| |
| bool eliminated = false; |
| |
| switch (node.op()) { |
| case CheckArgumentsNotCreated: { |
| if (!isEmptySpeculation( |
| m_state.variables().operand( |
| m_graph.argumentsRegisterFor(node.codeOrigin)).m_type)) |
| break; |
| ASSERT(node.refCount() == 1); |
| node.setOpAndDefaultFlags(Phantom); |
| eliminated = true; |
| break; |
| } |
| |
| // FIXME: This would be a great place to remove CheckStructure's. |
| |
| default: |
| break; |
| } |
| |
| if (eliminated) { |
| changed = true; |
| continue; |
| } |
| |
| m_state.execute(indexInBlock); |
| if (!node.shouldGenerate() |
| || m_state.didClobber() |
| || node.hasConstant()) |
| continue; |
| JSValue value = m_state.forNode(nodeIndex).value(); |
| if (!value) |
| continue; |
| |
| Node phantom(Phantom, node.codeOrigin); |
| |
| if (node.op() == GetLocal) { |
| NodeIndex previousLocalAccess = NoNode; |
| if (block->variablesAtHead.operand(node.local()) == nodeIndex |
| && m_graph[node.child1()].op() == Phi) { |
| // We expect this to be the common case. |
| ASSERT(block->isInPhis(node.child1().index())); |
| previousLocalAccess = node.child1().index(); |
| block->variablesAtHead.operand(node.local()) = previousLocalAccess; |
| } else { |
| ASSERT(indexInBlock > 0); |
| // Must search for the previous access to this local. |
| for (BlockIndex subIndexInBlock = indexInBlock; subIndexInBlock--;) { |
| NodeIndex subNodeIndex = block->at(subIndexInBlock); |
| Node& subNode = m_graph[subNodeIndex]; |
| if (!subNode.shouldGenerate()) |
| continue; |
| if (!subNode.hasVariableAccessData()) |
| continue; |
| if (subNode.local() != node.local()) |
| continue; |
| // The two must have been unified. |
| ASSERT(subNode.variableAccessData() == node.variableAccessData()); |
| previousLocalAccess = subNodeIndex; |
| break; |
| } |
| if (previousLocalAccess == NoNode) { |
| // The previous access must have been a Phi. |
| for (BlockIndex phiIndexInBlock = block->phis.size(); phiIndexInBlock--;) { |
| NodeIndex phiNodeIndex = block->phis[phiIndexInBlock]; |
| Node& phiNode = m_graph[phiNodeIndex]; |
| if (!phiNode.shouldGenerate()) |
| continue; |
| if (phiNode.local() != node.local()) |
| continue; |
| // The two must have been unified. |
| ASSERT(phiNode.variableAccessData() == node.variableAccessData()); |
| previousLocalAccess = phiNodeIndex; |
| break; |
| } |
| ASSERT(previousLocalAccess != NoNode); |
| } |
| } |
| |
| ASSERT(previousLocalAccess != NoNode); |
| |
| NodeIndex tailNodeIndex = block->variablesAtTail.operand(node.local()); |
| if (tailNodeIndex == nodeIndex) |
| block->variablesAtTail.operand(node.local()) = previousLocalAccess; |
| else { |
| ASSERT(m_graph[tailNodeIndex].op() == Flush |
| || m_graph[tailNodeIndex].op() == SetLocal); |
| } |
| } |
| |
| phantom.children = node.children; |
| phantom.ref(); |
| |
| m_graph.convertToConstant(nodeIndex, value); |
| NodeIndex phantomNodeIndex = m_graph.size(); |
| m_graph.append(phantom); |
| m_insertionSet.append(indexInBlock, phantomNodeIndex); |
| |
| changed = true; |
| } |
| m_state.reset(); |
| m_insertionSet.execute(*block); |
| |
| return changed; |
| } |
| |
| // This is necessary because the CFA may reach conclusions about constants based on its |
| // assumption that certain code must exit, but then those constants may lead future |
| // reexecutions of the CFA to believe that the same code will now no longer exit. Thus |
| // to ensure soundness, we must paint unreachable code as such, by inserting an |
| // unconditional ForceOSRExit wherever we find that a node would have always exited. |
| // This will only happen in cases where we are making static speculations, or we're |
| // making totally wrong speculations due to imprecision on the prediction propagator. |
| bool paintUnreachableCode(BlockIndex blockIndex) |
| { |
| bool changed = false; |
| |
| #if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE) |
| dataLog("Painting unreachable code in Block #%u.\n", blockIndex); |
| #endif |
| BasicBlock* block = m_graph.m_blocks[blockIndex].get(); |
| m_state.beginBasicBlock(block); |
| |
| for (unsigned indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) { |
| m_state.execute(indexInBlock); |
| if (m_state.isValid()) |
| continue; |
| |
| NodeIndex nodeIndex = block->at(indexInBlock); |
| Node& node = m_graph[nodeIndex]; |
| switch (node.op()) { |
| case Return: |
| case Throw: |
| case ThrowReferenceError: |
| case ForceOSRExit: |
| // Do nothing. These nodes will already do the right thing. |
| break; |
| |
| default: |
| Node forceOSRExit(ForceOSRExit, node.codeOrigin); |
| forceOSRExit.ref(); |
| NodeIndex forceOSRExitIndex = m_graph.size(); |
| m_graph.append(forceOSRExit); |
| m_insertionSet.append(indexInBlock, forceOSRExitIndex); |
| changed = true; |
| break; |
| } |
| break; |
| } |
| m_state.reset(); |
| m_insertionSet.execute(*block); |
| |
| return changed; |
| } |
| |
| AbstractState m_state; |
| InsertionSet<NodeIndex> m_insertionSet; |
| }; |
| |
| bool performConstantFolding(Graph& graph) |
| { |
| SamplingRegion samplingRegion("DFG Constant Folding Phase"); |
| return runPhase<ConstantFoldingPhase>(graph); |
| } |
| |
| } } // namespace JSC::DFG |
| |
| #endif // ENABLE(DFG_JIT) |
| |
| |
