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feat(furc/SSA): insert phi nodes

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This commit is contained in:
Aleksander Krajewski
2026-08-18 17:50:34 +02:00
parent 5403c0e1a4
commit 12a131c2b8
1 changed files with 60 additions and 11 deletions
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furc/src/middle/ssa.cpp
+60 -11
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@@ -31,6 +31,10 @@ struct block_info {
std::unordered_set<std::size_t> df;
};
struct register_info {
std::unordered_set<std::size_t> sites; // Definition Sites
};
void rpo_dfs(std::unordered_set<std::size_t>& visited,
std::vector<std::size_t>& order,
std::size_t block,
@@ -65,28 +69,43 @@ std::size_t intersect(std::vector<block_info>& blocks, std::size_t b1, std::size
}
void process_function(ir_function& func) {
std::vector<block_info> blocks(func.blocks.size());
std::vector<block_info> blocks(func.blocks.size());
std::vector<register_info> registers(func.regCount);
std::unordered_set<std::uint64_t> nonLocals;
// 1. Compute CFG
for (std::size_t i = 0; i < func.blocks.size(); ++i) {
const auto& block = func.blocks[i];
if (block.instructions.empty()) continue;
for (const auto& instr : block.instructions) {
for (const auto& op : instr.sources) {
if (op.type != ir_operand::Register) continue;
const auto& reg = registers[op.value.reg.name];
if (reg.sites.find(i) != reg.sites.end()) continue;
nonLocals.insert(op.value.reg.name);
}
if (!instr.destination.has_value() || instr.destination->type != ir_operand::Register) continue;
registers[instr.destination->value.reg.name].sites.insert(i);
}
const auto& termInstr = block.instructions.back();
switch (termInstr.type) {
case ir_instruction::Branch: {
const auto& src = termInstr.sources.front();
if (src.type != ir_operand::Block) throw std::runtime_error("invalid operand");
blocks[src.value.block].preds.insert(i);
blocks[i].sucs.insert(src.value.block);
const auto& dst = termInstr.destination.value();
if (dst.type != ir_operand::Block) throw std::runtime_error("invalid operand");
blocks[dst.value.block].preds.insert(i);
blocks[i].sucs.insert(dst.value.block);
} break;
case ir_instruction::BranchCond: {
const auto& src = termInstr.sources.front();
if (src.type != ir_operand::Block) throw std::runtime_error("invalid operand");
blocks[src.value.blockPair.first].preds.insert(i);
blocks[src.value.blockPair.second].preds.insert(i);
blocks[i].preds.insert(src.value.blockPair.first);
blocks[i].preds.insert(src.value.blockPair.second);
const auto& dst = termInstr.destination.value();
if (dst.type != ir_operand::BlockPair) throw std::runtime_error("invalid operand");
blocks[dst.value.blockPair.first].preds.insert(i);
blocks[dst.value.blockPair.second].preds.insert(i);
blocks[i].preds.insert(dst.value.blockPair.first);
blocks[i].preds.insert(dst.value.blockPair.second);
} break;
default: break;
}
@@ -131,6 +150,36 @@ void process_function(ir_function& func) {
}
}
}
// 4. Inserting Phi-nodes (Semi-Pruned SSA form)
std::vector<std::size_t> worklist;
for (std::size_t i = 0; i < registers.size(); ++i) {
const auto& reg = registers[i];
if (reg.sites.size() < 2 || nonLocals.find(i) == nonLocals.end()) continue;
worklist.insert(worklist.end(), reg.sites.begin(), reg.sites.end());
std::unordered_set<std::size_t> done;
while (!worklist.empty()) {
const auto blockIdx = worklist.back();
worklist.pop_back();
for (auto frontier : blocks[blockIdx].df) {
if (done.find(frontier) != done.end()) continue;
done.insert(frontier);
auto& target = func.blocks[frontier];
ir_instruction instr = { ir_instruction::Phi };
for (const auto& pred : blocks[frontier].preds)
instr.sources.emplace_back(ir_operand::PhiPair, i, pred);
target.instructions.emplace(target.instructions.begin(), std::move(instr));
if (reg.sites.find(frontier) == reg.sites.end()) worklist.push_back(frontier);
}
}
}
}
} // namespace