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#include "slang-ir-simplify-cfg.h"
#include "slang-ir-insts.h"
#include "slang-ir.h"
namespace Slang
{
bool processFunc(IRFunc* func)
{
auto firstBlock = func->getFirstBlock();
if (!firstBlock)
return false;
bool changed = false;
List<IRBlock*> workList;
HashSet<IRBlock*> processedBlock;
workList.add(func->getFirstBlock());
while (workList.getCount())
{
auto block = workList.getFirst();
workList.fastRemoveAt(0);
while (block)
{
// If `block` does not end with an unconditional branch, bail.
if (block->getTerminator()->getOp() != kIROp_unconditionalBranch)
break;
auto branch = as<IRUnconditionalBranch>(block->getTerminator());
auto successor = branch->getTargetBlock();
// Only perform the merge if `block` is the only predecessor of `successor`.
// We also need to make sure not to merge a block that serves as the
// merge point in CFG. Such blocks will have more than one use.
if (successor->hasMoreThanOneUse())
break;
changed = true;
Index paramIndex = 0;
auto inst = successor->getFirstDecorationOrChild();
while (inst)
{
auto next = inst->getNextInst();
if (inst->getOp() == kIROp_Param)
{
inst->replaceUsesWith(branch->getArg(paramIndex));
paramIndex++;
}
else
{
inst->removeFromParent();
inst->insertAtEnd(block);
}
inst = next;
}
branch->removeAndDeallocate();
assert(!successor->hasUses());
successor->removeAndDeallocate();
}
for (auto successor : block->getSuccessors())
{
if (processedBlock.Add(successor))
{
workList.add(successor);
}
}
}
return changed;
}
bool simplifyCFG(IRModule* module)
{
bool changed = false;
for (auto inst : module->getGlobalInsts())
{
if (auto func = as<IRFunc>(inst))
{
changed |= processFunc(func);
}
}
return changed;
}
} // namespace Slang
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