static void linkAllBlocks()
{
auto e = gBlockMap.end();
auto i = gBlockMap.begin();
while(i!=e) {
Block *block = (i++)->second;
linkBlock(block);
}
}
bool SimplifyControlFlowGraphPass::_mergeExitBlocks(ir::IRKernel& k)
{
typedef std::unordered_map<ir::ControlFlowGraph::iterator,
ir::ControlFlowGraph::instruction_iterator> BlockMap;
report(" Merging exit blocks...");
BlockMap exitBlocks;
// Find all blocks with exit instructions
for(ir::ControlFlowGraph::iterator block = k.cfg()->begin();
block != k.cfg()->end(); ++block)
{
for(ir::ControlFlowGraph::instruction_iterator
instruction = block->instructions.begin();
instruction != block->instructions.end(); ++instruction)
{
ir::PTXInstruction& ptx =
static_cast<ir::PTXInstruction&>(**instruction);
if(ptx.isExit() && ptx.opcode != ir::PTXInstruction::Trap)
{
// There should be an edge to the exit block
assertM(block->find_out_edge(k.cfg()->get_exit_block()) !=
block->out_edges.end(), "No edge from " << block->label()
<< " to exit node.");
exitBlocks.insert(std::make_pair(block, instruction));
break;
}
}
}
// If there is only one/zero blocks, then don't change anything
if(exitBlocks.size() < 2)
{
if(exitBlocks.size() == 1)
{
ir::PTXInstruction& ptx =
static_cast<ir::PTXInstruction&>(**exitBlocks.begin()->second);
if(k.function())
{
ptx.opcode = ir::PTXInstruction::Ret;
}
else
{
ptx.opcode = ir::PTXInstruction::Exit;
}
}
return false;
}
// Otherwise...
// 1) create a new exit block
ir::ControlFlowGraph::iterator newExit = k.cfg()->insert_block(
ir::BasicBlock(k.cfg()->newId()));
ir::BasicBlock::EdgePointerVector deletedEdges =
k.cfg()->get_exit_block()->in_edges;
// 1a) Create edges targetting the new block
for(ir::ControlFlowGraph::edge_pointer_iterator edge = deletedEdges.begin();
edge != deletedEdges.end(); ++edge)
{
k.cfg()->insert_edge(ir::Edge((*edge)->head, newExit, (*edge)->type));
k.cfg()->remove_edge(*edge);
}
k.cfg()->insert_edge(ir::Edge(newExit, k.cfg()->get_exit_block(),
ir::Edge::FallThrough));
// 2) Delete the instructions from their blocks
for(BlockMap::iterator block = exitBlocks.begin();
block != exitBlocks.end(); ++block)
{
report(" merging block " << block->first->label());
// 2a) Insert a branch from blocks with branch edges
ir::ControlFlowGraph::edge_pointer_iterator edge =
newExit->find_in_edge(block->first);
if((*edge)->type == ir::Edge::Branch)
{
ir::PTXInstruction* newBranch = new ir::PTXInstruction(
ir::PTXInstruction::Bra, ir::PTXOperand(newExit->label()));
newBranch->uni = true;
block->first->instructions.push_back(newBranch);
}
delete *block->second;
block->first->instructions.erase(block->second);
}
// 3 Add an appropriate exit instruction to the new exit block
if(k.function())
{
newExit->instructions.push_back(
new ir::PTXInstruction(ir::PTXInstruction::Ret));
}
else
{
newExit->instructions.push_back(
new ir::PTXInstruction(ir::PTXInstruction::Exit));
}
return true;
}
