void InPlaceAbstractState::beginBasicBlock(BasicBlock* basicBlock)
{
ASSERT(!m_block);
ASSERT(basicBlock->variablesAtHead.numberOfLocals() == basicBlock->valuesAtHead.numberOfLocals());
ASSERT(basicBlock->variablesAtTail.numberOfLocals() == basicBlock->valuesAtTail.numberOfLocals());
ASSERT(basicBlock->variablesAtHead.numberOfLocals() == basicBlock->variablesAtTail.numberOfLocals());
for (size_t i = 0; i < basicBlock->size(); i++)
forNode(basicBlock->at(i)).clear();
m_variables = basicBlock->valuesAtHead;
if (m_graph.m_form == SSA) {
HashMap<Node*, AbstractValue>::iterator iter = basicBlock->ssa->valuesAtHead.begin();
HashMap<Node*, AbstractValue>::iterator end = basicBlock->ssa->valuesAtHead.end();
for (; iter != end; ++iter)
forNode(iter->key) = iter->value;
}
basicBlock->cfaShouldRevisit = false;
basicBlock->cfaHasVisited = true;
m_block = basicBlock;
m_isValid = true;
m_foundConstants = false;
m_branchDirection = InvalidBranchDirection;
m_structureClobberState = basicBlock->cfaStructureClobberStateAtHead;
}
bool InPlaceAbstractState::mergeStateAtTail(AbstractValue& destination, AbstractValue& inVariable, Node* node)
{
if (!node)
return false;
AbstractValue source;
switch (node->op()) {
case Phi:
case SetArgument:
case PhantomLocal:
case Flush:
// The block transfers the value from head to tail.
source = inVariable;
break;
case GetLocal:
// The block refines the value with additional speculations.
source = forNode(node);
break;
case SetLocal:
// The block sets the variable, and potentially refines it, both
// before and after setting it.
source = forNode(node->child1());
if (node->variableAccessData()->flushFormat() == FlushedDouble)
RELEASE_ASSERT(!(source.m_type & ~SpecFullDouble));
break;
default:
RELEASE_ASSERT_NOT_REACHED();
break;
}
if (destination == source) {
// Abstract execution did not change the output value of the variable, for this
// basic block, on this iteration.
return false;
}
// Abstract execution reached a new conclusion about the speculations reached about
// this variable after execution of this basic block. Update the state, and return
// true to indicate that the fixpoint must go on!
destination = source;
return true;
}
bool InPlaceAbstractState::mergeStateAtTail(AbstractValue& destination, AbstractValue& inVariable, Node* node)
{
if (!node)
return false;
AbstractValue source;
if (node->variableAccessData()->isCaptured()) {
// If it's captured then we know that whatever value was stored into the variable last is the
// one we care about. This is true even if the variable at tail is dead, which might happen if
// the last thing we did to the variable was a GetLocal and then ended up now using the
// GetLocal's result.
source = inVariable;
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Transfering ");
source.dump(WTF::dataFile());
dataLogF(" from last access due to captured variable.\n");
#endif
} else {
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" It's live, node @%u.\n", node->index());
#endif
switch (node->op()) {
case Phi:
case SetArgument:
case PhantomLocal:
case Flush:
// The block transfers the value from head to tail.
source = inVariable;
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Transfering ");
source.dump(WTF::dataFile());
dataLogF(" from head to tail.\n");
#endif
break;
case GetLocal:
// The block refines the value with additional speculations.
source = forNode(node);
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Refining to ");
source.dump(WTF::dataFile());
dataLogF("\n");
#endif
break;
case SetLocal:
// The block sets the variable, and potentially refines it, both
// before and after setting it.
if (node->variableAccessData()->shouldUseDoubleFormat()) {
// FIXME: This unnecessarily loses precision.
source.setType(SpecDouble);
} else
source = forNode(node->child1());
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Setting to ");
source.dump(WTF::dataFile());
dataLogF("\n");
#endif
break;
default:
RELEASE_ASSERT_NOT_REACHED();
break;
}
}
if (destination == source) {
// Abstract execution did not change the output value of the variable, for this
// basic block, on this iteration.
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Not changed!\n");
#endif
return false;
}
// Abstract execution reached a new conclusion about the speculations reached about
// this variable after execution of this basic block. Update the state, and return
// true to indicate that the fixpoint must go on!
destination = source;
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Changed!\n");
#endif
return true;
}
bool InPlaceAbstractState::endBasicBlock(MergeMode mergeMode)
{
ASSERT(m_block);
BasicBlock* block = m_block; // Save the block for successor merging.
block->cfaFoundConstants = m_foundConstants;
block->cfaDidFinish = m_isValid;
block->cfaBranchDirection = m_branchDirection;
if (!m_isValid) {
reset();
return false;
}
bool changed = false;
if (mergeMode != DontMerge || !ASSERT_DISABLED) {
switch (m_graph.m_form) {
case ThreadedCPS: {
for (size_t argument = 0; argument < block->variablesAtTail.numberOfArguments(); ++argument) {
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Merging state for argument %zu.\n", argument);
#endif
AbstractValue& destination = block->valuesAtTail.argument(argument);
changed |= mergeStateAtTail(destination, m_variables.argument(argument), block->variablesAtTail.argument(argument));
}
for (size_t local = 0; local < block->variablesAtTail.numberOfLocals(); ++local) {
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Merging state for local %zu.\n", local);
#endif
AbstractValue& destination = block->valuesAtTail.local(local);
changed |= mergeStateAtTail(destination, m_variables.local(local), block->variablesAtTail.local(local));
}
break;
}
case SSA: {
for (size_t i = 0; i < block->valuesAtTail.size(); ++i)
changed |= block->valuesAtTail[i].merge(m_variables[i]);
HashSet<Node*>::iterator iter = block->ssa->liveAtTail.begin();
HashSet<Node*>::iterator end = block->ssa->liveAtTail.end();
for (; iter != end; ++iter) {
Node* node = *iter;
changed |= block->ssa->valuesAtTail.find(node)->value.merge(forNode(node));
}
break;
}
default:
RELEASE_ASSERT_NOT_REACHED();
}
}
ASSERT(mergeMode != DontMerge || !changed);
#if DFG_ENABLE(DEBUG_PROPAGATION_VERBOSE)
dataLogF(" Branch direction = %s\n", branchDirectionToString(m_branchDirection));
#endif
reset();
if (mergeMode != MergeToSuccessors)
return changed;
return mergeToSuccessors(block);
}
static MemSource forNode(const Node &node) {
return forNode(node.physicalId());
}