415 lines
15 KiB
C++
415 lines
15 KiB
C++
// Copyright 2021 yuzu Emulator Project
|
|
// Licensed under GPLv2 or any later version
|
|
// Refer to the license.txt file included.
|
|
|
|
// This file implements the SSA rewriting algorithm proposed in
|
|
//
|
|
// Simple and Efficient Construction of Static Single Assignment Form.
|
|
// Braun M., Buchwald S., Hack S., Leiba R., Mallon C., Zwinkau A. (2013)
|
|
// In: Jhala R., De Bosschere K. (eds)
|
|
// Compiler Construction. CC 2013.
|
|
// Lecture Notes in Computer Science, vol 7791.
|
|
// Springer, Berlin, Heidelberg
|
|
//
|
|
// https://link.springer.com/chapter/10.1007/978-3-642-37051-9_6
|
|
//
|
|
|
|
#include <deque>
|
|
#include <span>
|
|
#include <variant>
|
|
#include <vector>
|
|
|
|
#include <boost/container/flat_map.hpp>
|
|
#include <boost/container/flat_set.hpp>
|
|
|
|
#include "shader_recompiler/frontend/ir/basic_block.h"
|
|
#include "shader_recompiler/frontend/ir/opcodes.h"
|
|
#include "shader_recompiler/frontend/ir/pred.h"
|
|
#include "shader_recompiler/frontend/ir/reg.h"
|
|
#include "shader_recompiler/frontend/ir/value.h"
|
|
#include "shader_recompiler/ir_opt/passes.h"
|
|
|
|
namespace Shader::Optimization {
|
|
namespace {
|
|
struct FlagTag {
|
|
auto operator<=>(const FlagTag&) const noexcept = default;
|
|
};
|
|
struct ZeroFlagTag : FlagTag {};
|
|
struct SignFlagTag : FlagTag {};
|
|
struct CarryFlagTag : FlagTag {};
|
|
struct OverflowFlagTag : FlagTag {};
|
|
|
|
struct GotoVariable : FlagTag {
|
|
GotoVariable() = default;
|
|
explicit GotoVariable(u32 index_) : index{index_} {}
|
|
|
|
auto operator<=>(const GotoVariable&) const noexcept = default;
|
|
|
|
u32 index;
|
|
};
|
|
|
|
struct IndirectBranchVariable {
|
|
auto operator<=>(const IndirectBranchVariable&) const noexcept = default;
|
|
};
|
|
|
|
using Variant = std::variant<IR::Reg, IR::Pred, ZeroFlagTag, SignFlagTag, CarryFlagTag,
|
|
OverflowFlagTag, GotoVariable, IndirectBranchVariable>;
|
|
using ValueMap = boost::container::flat_map<IR::Block*, IR::Value>;
|
|
|
|
struct DefTable {
|
|
const IR::Value& Def(IR::Block* block, IR::Reg variable) {
|
|
return block->SsaRegValue(variable);
|
|
}
|
|
void SetDef(IR::Block* block, IR::Reg variable, const IR::Value& value) {
|
|
block->SetSsaRegValue(variable, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, IR::Pred variable) {
|
|
return preds[IR::PredIndex(variable)][block];
|
|
}
|
|
void SetDef(IR::Block* block, IR::Pred variable, const IR::Value& value) {
|
|
preds[IR::PredIndex(variable)].insert_or_assign(block, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, GotoVariable variable) {
|
|
return goto_vars[variable.index][block];
|
|
}
|
|
void SetDef(IR::Block* block, GotoVariable variable, const IR::Value& value) {
|
|
goto_vars[variable.index].insert_or_assign(block, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, IndirectBranchVariable) {
|
|
return indirect_branch_var[block];
|
|
}
|
|
void SetDef(IR::Block* block, IndirectBranchVariable, const IR::Value& value) {
|
|
indirect_branch_var.insert_or_assign(block, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, ZeroFlagTag) {
|
|
return zero_flag[block];
|
|
}
|
|
void SetDef(IR::Block* block, ZeroFlagTag, const IR::Value& value) {
|
|
zero_flag.insert_or_assign(block, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, SignFlagTag) {
|
|
return sign_flag[block];
|
|
}
|
|
void SetDef(IR::Block* block, SignFlagTag, const IR::Value& value) {
|
|
sign_flag.insert_or_assign(block, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, CarryFlagTag) {
|
|
return carry_flag[block];
|
|
}
|
|
void SetDef(IR::Block* block, CarryFlagTag, const IR::Value& value) {
|
|
carry_flag.insert_or_assign(block, value);
|
|
}
|
|
|
|
const IR::Value& Def(IR::Block* block, OverflowFlagTag) {
|
|
return overflow_flag[block];
|
|
}
|
|
void SetDef(IR::Block* block, OverflowFlagTag, const IR::Value& value) {
|
|
overflow_flag.insert_or_assign(block, value);
|
|
}
|
|
|
|
std::array<ValueMap, IR::NUM_USER_PREDS> preds;
|
|
boost::container::flat_map<u32, ValueMap> goto_vars;
|
|
ValueMap indirect_branch_var;
|
|
ValueMap zero_flag;
|
|
ValueMap sign_flag;
|
|
ValueMap carry_flag;
|
|
ValueMap overflow_flag;
|
|
};
|
|
|
|
IR::Opcode UndefOpcode(IR::Reg) noexcept {
|
|
return IR::Opcode::UndefU32;
|
|
}
|
|
|
|
IR::Opcode UndefOpcode(IR::Pred) noexcept {
|
|
return IR::Opcode::UndefU1;
|
|
}
|
|
|
|
IR::Opcode UndefOpcode(const FlagTag&) noexcept {
|
|
return IR::Opcode::UndefU1;
|
|
}
|
|
|
|
IR::Opcode UndefOpcode(IndirectBranchVariable) noexcept {
|
|
return IR::Opcode::UndefU32;
|
|
}
|
|
|
|
enum class Status {
|
|
Start,
|
|
SetValue,
|
|
PreparePhiArgument,
|
|
PushPhiArgument,
|
|
};
|
|
|
|
template <typename Type>
|
|
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 <typename Type>
|
|
void WriteVariable(Type variable, IR::Block* block, const IR::Value& value) {
|
|
current_def.SetDef(block, variable, value);
|
|
}
|
|
|
|
template <typename Type>
|
|
IR::Value ReadVariable(Type variable, IR::Block* root_block) {
|
|
boost::container::small_vector<ReadState<Type>, 64> stack{
|
|
ReadState<Type>(nullptr),
|
|
ReadState<Type>(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: {
|
|
if (const IR::Value& def = current_def.Def(block, variable); !def.IsEmpty()) {
|
|
stack.back().result = def;
|
|
} else if (!block->IsSsaSealed()) {
|
|
// Incomplete CFG
|
|
IR::Inst* phi{&*block->PrependNewInst(block->begin(), IR::Opcode::Phi)};
|
|
phi->SetFlags(IR::TypeOf(UndefOpcode(variable)));
|
|
|
|
incomplete_phis[block].insert_or_assign(variable, phi);
|
|
stack.back().result = IR::Value{&*phi};
|
|
} else if (const std::span imm_preds = block->ImmPredecessors();
|
|
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)};
|
|
phi->SetFlags(IR::TypeOf(UndefOpcode(variable)));
|
|
|
|
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) {
|
|
const auto it{incomplete_phis.find(block)};
|
|
if (it != incomplete_phis.end()) {
|
|
for (auto& pair : it->second) {
|
|
auto& variant{pair.first};
|
|
auto& phi{pair.second};
|
|
std::visit([&](auto& variable) { AddPhiOperands(variable, *phi, block); }, variant);
|
|
}
|
|
}
|
|
block->SsaSeal();
|
|
}
|
|
|
|
private:
|
|
template <typename Type>
|
|
IR::Value AddPhiOperands(Type variable, IR::Inst& phi, IR::Block* block) {
|
|
for (IR::Block* const imm_pred : block->ImmPredecessors()) {
|
|
phi.AddPhiOperand(imm_pred, ReadVariable(variable, imm_pred));
|
|
}
|
|
return TryRemoveTrivialPhi(phi, block, UndefOpcode(variable));
|
|
}
|
|
|
|
IR::Value TryRemoveTrivialPhi(IR::Inst& phi, IR::Block* block, IR::Opcode undef_opcode) {
|
|
IR::Value same;
|
|
const size_t num_args{phi.NumArgs()};
|
|
for (size_t arg_index = 0; arg_index < num_args; ++arg_index) {
|
|
const IR::Value& op{phi.Arg(arg_index)};
|
|
if (op.Resolve() == same.Resolve() || op == IR::Value{&phi}) {
|
|
// Unique value or self-reference
|
|
continue;
|
|
}
|
|
if (!same.IsEmpty()) {
|
|
// The phi merges at least two values: not trivial
|
|
return IR::Value{&phi};
|
|
}
|
|
same = op;
|
|
}
|
|
// Remove the phi node from the block, it will be reinserted
|
|
IR::Block::InstructionList& list{block->Instructions()};
|
|
list.erase(IR::Block::InstructionList::s_iterator_to(phi));
|
|
|
|
// Find the first non-phi instruction and use it as an insertion point
|
|
IR::Block::iterator reinsert_point{std::ranges::find_if_not(list, IR::IsPhi)};
|
|
if (same.IsEmpty()) {
|
|
// The phi is unreachable or in the start block
|
|
// Insert an undefined instruction and make it the phi node replacement
|
|
// The "phi" node reinsertion point is specified after this instruction
|
|
reinsert_point = block->PrependNewInst(reinsert_point, undef_opcode);
|
|
same = IR::Value{&*reinsert_point};
|
|
++reinsert_point;
|
|
}
|
|
// Reinsert the phi node and reroute all its uses to the "same" value
|
|
list.insert(reinsert_point, phi);
|
|
phi.ReplaceUsesWith(same);
|
|
// TODO: Try to recursively remove all phi users, which might have become trivial
|
|
return same;
|
|
}
|
|
|
|
boost::container::flat_map<IR::Block*, boost::container::flat_map<Variant, IR::Inst*>>
|
|
incomplete_phis;
|
|
DefTable current_def;
|
|
};
|
|
|
|
void VisitInst(Pass& pass, IR::Block* block, IR::Inst& inst) {
|
|
switch (inst.GetOpcode()) {
|
|
case IR::Opcode::SetRegister:
|
|
if (const IR::Reg reg{inst.Arg(0).Reg()}; reg != IR::Reg::RZ) {
|
|
pass.WriteVariable(reg, block, inst.Arg(1));
|
|
}
|
|
break;
|
|
case IR::Opcode::SetPred:
|
|
if (const IR::Pred pred{inst.Arg(0).Pred()}; pred != IR::Pred::PT) {
|
|
pass.WriteVariable(pred, block, inst.Arg(1));
|
|
}
|
|
break;
|
|
case IR::Opcode::SetGotoVariable:
|
|
pass.WriteVariable(GotoVariable{inst.Arg(0).U32()}, block, inst.Arg(1));
|
|
break;
|
|
case IR::Opcode::SetIndirectBranchVariable:
|
|
pass.WriteVariable(IndirectBranchVariable{}, block, inst.Arg(0));
|
|
break;
|
|
case IR::Opcode::SetZFlag:
|
|
pass.WriteVariable(ZeroFlagTag{}, block, inst.Arg(0));
|
|
break;
|
|
case IR::Opcode::SetSFlag:
|
|
pass.WriteVariable(SignFlagTag{}, block, inst.Arg(0));
|
|
break;
|
|
case IR::Opcode::SetCFlag:
|
|
pass.WriteVariable(CarryFlagTag{}, block, inst.Arg(0));
|
|
break;
|
|
case IR::Opcode::SetOFlag:
|
|
pass.WriteVariable(OverflowFlagTag{}, block, inst.Arg(0));
|
|
break;
|
|
case IR::Opcode::GetRegister:
|
|
if (const IR::Reg reg{inst.Arg(0).Reg()}; reg != IR::Reg::RZ) {
|
|
inst.ReplaceUsesWith(pass.ReadVariable(reg, block));
|
|
}
|
|
break;
|
|
case IR::Opcode::GetPred:
|
|
if (const IR::Pred pred{inst.Arg(0).Pred()}; pred != IR::Pred::PT) {
|
|
inst.ReplaceUsesWith(pass.ReadVariable(pred, block));
|
|
}
|
|
break;
|
|
case IR::Opcode::GetGotoVariable:
|
|
inst.ReplaceUsesWith(pass.ReadVariable(GotoVariable{inst.Arg(0).U32()}, block));
|
|
break;
|
|
case IR::Opcode::GetIndirectBranchVariable:
|
|
inst.ReplaceUsesWith(pass.ReadVariable(IndirectBranchVariable{}, block));
|
|
break;
|
|
case IR::Opcode::GetZFlag:
|
|
inst.ReplaceUsesWith(pass.ReadVariable(ZeroFlagTag{}, block));
|
|
break;
|
|
case IR::Opcode::GetSFlag:
|
|
inst.ReplaceUsesWith(pass.ReadVariable(SignFlagTag{}, block));
|
|
break;
|
|
case IR::Opcode::GetCFlag:
|
|
inst.ReplaceUsesWith(pass.ReadVariable(CarryFlagTag{}, block));
|
|
break;
|
|
case IR::Opcode::GetOFlag:
|
|
inst.ReplaceUsesWith(pass.ReadVariable(OverflowFlagTag{}, block));
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
void VisitBlock(Pass& pass, IR::Block* block) {
|
|
for (IR::Inst& inst : block->Instructions()) {
|
|
VisitInst(pass, block, inst);
|
|
}
|
|
pass.SealBlock(block);
|
|
}
|
|
|
|
IR::Type GetConcreteType(IR::Inst* inst) {
|
|
std::deque<IR::Inst*> queue;
|
|
queue.push_back(inst);
|
|
while (!queue.empty()) {
|
|
IR::Inst* current = queue.front();
|
|
queue.pop_front();
|
|
const size_t num_args{current->NumArgs()};
|
|
for (size_t i = 0; i < num_args; ++i) {
|
|
const auto set_type = current->Arg(i).Type();
|
|
if (set_type != IR::Type::Opaque) {
|
|
return set_type;
|
|
}
|
|
if (!current->Arg(i).IsImmediate()) {
|
|
queue.push_back(current->Arg(i).Inst());
|
|
}
|
|
}
|
|
}
|
|
return IR::Type::Opaque;
|
|
}
|
|
} // Anonymous namespace
|
|
|
|
void SsaRewritePass(IR::Program& program) {
|
|
Pass pass;
|
|
const auto end{program.post_order_blocks.rend()};
|
|
for (auto block = program.post_order_blocks.rbegin(); block != end; ++block) {
|
|
VisitBlock(pass, *block);
|
|
}
|
|
for (auto block = program.post_order_blocks.rbegin(); block != end; ++block) {
|
|
for (IR::Inst& inst : (*block)->Instructions()) {
|
|
if (inst.GetOpcode() == IR::Opcode::Phi) {
|
|
if (inst.Type() == IR::Type::Opaque) {
|
|
inst.SetFlags(GetConcreteType(&inst));
|
|
}
|
|
inst.OrderPhiArgs();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
} // namespace Shader::Optimization
|