From 417fb5d385daa0fb40329709e6b4a53937580989 Mon Sep 17 00:00:00 2001 From: ReinUsesLisp Date: Mon, 5 Apr 2021 19:10:55 -0300 Subject: [PATCH] shader: Move recursive SSA rewrite to the heap --- .../ir_opt/ssa_rewrite_pass.cpp | 118 +++++++++++++----- 1 file changed, 89 insertions(+), 29 deletions(-) diff --git a/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp b/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp index 259233746..ca36253d1 100644 --- a/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp +++ b/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp @@ -119,6 +119,26 @@ IR::Opcode UndefOpcode(IndirectBranchVariable) noexcept { return inst.Opcode() == IR::Opcode::Phi; } +enum class Status { + Start, + SetValue, + PreparePhiArgument, + PushPhiArgument, +}; + +template +struct ReadState { + ReadState(IR::Block* block_) : block{block_} {} + ReadState() = default; + + IR::Block* block{}; + IR::Value result{}; + IR::Inst* phi{}; + IR::Block* const* pred_it{}; + IR::Block* const* pred_end{}; + Status pc{Status::Start}; +}; + class Pass { public: template @@ -127,12 +147,75 @@ public: } template - IR::Value ReadVariable(Type variable, IR::Block* block) { - const ValueMap& def{current_def[variable]}; - if (const auto it{def.find(block)}; it != def.end()) { - return it->second; - } - return ReadVariableRecursive(variable, block); + IR::Value ReadVariable(Type variable, IR::Block* root_block) { + boost::container::small_vector, 64> stack{ + ReadState(nullptr), + ReadState(root_block), + }; + const auto prepare_phi_operand{[&] { + if (stack.back().pred_it == stack.back().pred_end) { + IR::Inst* const phi{stack.back().phi}; + IR::Block* const block{stack.back().block}; + const IR::Value result{TryRemoveTrivialPhi(*phi, block, UndefOpcode(variable))}; + stack.pop_back(); + stack.back().result = result; + WriteVariable(variable, block, result); + } else { + IR::Block* const imm_pred{*stack.back().pred_it}; + stack.back().pc = Status::PushPhiArgument; + stack.emplace_back(imm_pred); + } + }}; + do { + IR::Block* const block{stack.back().block}; + switch (stack.back().pc) { + case Status::Start: { + const ValueMap& def{current_def[variable]}; + if (const auto it{def.find(block)}; it != def.end()) { + stack.back().result = it->second; + } else if (!sealed_blocks.contains(block)) { + // Incomplete CFG + IR::Inst* phi{&*block->PrependNewInst(block->begin(), IR::Opcode::Phi)}; + incomplete_phis[block].insert_or_assign(variable, phi); + stack.back().result = IR::Value{&*phi}; + } else if (const std::span imm_preds{block->ImmediatePredecessors()}; + imm_preds.size() == 1) { + // Optimize the common case of one predecessor: no phi needed + stack.back().pc = Status::SetValue; + stack.emplace_back(imm_preds.front()); + break; + } else { + // Break potential cycles with operandless phi + IR::Inst* const phi{&*block->PrependNewInst(block->begin(), IR::Opcode::Phi)}; + WriteVariable(variable, block, IR::Value{phi}); + + stack.back().phi = phi; + stack.back().pred_it = imm_preds.data(); + stack.back().pred_end = imm_preds.data() + imm_preds.size(); + prepare_phi_operand(); + break; + } + } + [[fallthrough]]; + case Status::SetValue: { + const IR::Value result{stack.back().result}; + WriteVariable(variable, block, result); + stack.pop_back(); + stack.back().result = result; + break; + } + case Status::PushPhiArgument: { + IR::Inst* const phi{stack.back().phi}; + phi->AddPhiOperand(*stack.back().pred_it, stack.back().result); + ++stack.back().pred_it; + } + [[fallthrough]]; + case Status::PreparePhiArgument: + prepare_phi_operand(); + break; + } + } while (stack.size() > 1); + return stack.back().result; } void SealBlock(IR::Block* block) { @@ -146,29 +229,6 @@ public: } private: - template - IR::Value ReadVariableRecursive(Type variable, IR::Block* block) { - IR::Value val; - if (!sealed_blocks.contains(block)) { - // Incomplete CFG - IR::Inst* phi{&*block->PrependNewInst(block->begin(), IR::Opcode::Phi)}; - incomplete_phis[block].insert_or_assign(variable, phi); - val = IR::Value{&*phi}; - } else if (const std::span imm_preds{block->ImmediatePredecessors()}; - imm_preds.size() == 1) { - // Optimize the common case of one predecessor: no phi needed - val = ReadVariable(variable, imm_preds.front()); - } else { - // Break potential cycles with operandless phi - IR::Inst& phi_inst{*block->PrependNewInst(block->begin(), IR::Opcode::Phi)}; - val = IR::Value{&phi_inst}; - WriteVariable(variable, block, val); - val = AddPhiOperands(variable, phi_inst, block); - } - WriteVariable(variable, block, val); - return val; - } - template IR::Value AddPhiOperands(Type variable, IR::Inst& phi, IR::Block* block) { for (IR::Block* const imm_pred : block->ImmediatePredecessors()) {