// Copyright 2018 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <cstring>
#include <set>
#include <fmt/format.h>
#include "common/assert.h"
#include "common/common_types.h"
#include "video_core/engines/shader_bytecode.h"
#include "video_core/engines/shader_header.h"
#include "video_core/shader/shader_ir.h"
namespace VideoCommon::Shader {
using Tegra::Shader::Instruction;
using Tegra::Shader::OpCode;
namespace {
/// Merges exit method of two parallel branches.
constexpr ExitMethod ParallelExit(ExitMethod a, ExitMethod b) {
if (a == ExitMethod::Undetermined) {
return b;
}
if (b == ExitMethod::Undetermined) {
return a;
}
if (a == b) {
return a;
}
return ExitMethod::Conditional;
}
/**
* Returns whether the instruction at the specified offset is a 'sched' instruction.
* Sched instructions always appear before a sequence of 3 instructions.
*/
constexpr bool IsSchedInstruction(u32 offset, u32 main_offset) {
constexpr u32 SchedPeriod = 4;
u32 absolute_offset = offset - main_offset;
return (absolute_offset % SchedPeriod) == 0;
}
} // namespace
void ShaderIR::Decode() {
std::memcpy(&header, program_code.data(), sizeof(Tegra::Shader::Header));
std::set<u32> labels;
const ExitMethod exit_method = Scan(main_offset, MAX_PROGRAM_LENGTH, labels);
if (exit_method != ExitMethod::AlwaysEnd) {
UNREACHABLE_MSG("Program does not always end");
}
if (labels.empty()) {
basic_blocks.insert({main_offset, DecodeRange(main_offset, MAX_PROGRAM_LENGTH)});
return;
}
labels.insert(main_offset);
for (const u32 label : labels) {
const auto next_it = labels.lower_bound(label + 1);
const u32 next_label = next_it == labels.end() ? MAX_PROGRAM_LENGTH : *next_it;
basic_blocks.insert({label, DecodeRange(label, next_label)});
}
}
ExitMethod ShaderIR::Scan(u32 begin, u32 end, std::set<u32>& labels) {
const auto [iter, inserted] =
exit_method_map.emplace(std::make_pair(begin, end), ExitMethod::Undetermined);
ExitMethod& exit_method = iter->second;
if (!inserted)
return exit_method;
for (u32 offset = begin; offset != end && offset != MAX_PROGRAM_LENGTH; ++offset) {
coverage_begin = std::min(coverage_begin, offset);
coverage_end = std::max(coverage_end, offset + 1);
const Instruction instr = {program_code[offset]};
const auto opcode = OpCode::Decode(instr);
if (!opcode)
continue;
switch (opcode->get().GetId()) {
case OpCode::Id::EXIT: {
// The EXIT instruction can be predicated, which means that the shader can conditionally
// end on this instruction. We have to consider the case where the condition is not met
// and check the exit method of that other basic block.
using Tegra::Shader::Pred;
if (instr.pred.pred_index == static_cast<u64>(Pred::UnusedIndex)) {
return exit_method = ExitMethod::AlwaysEnd;
} else {
const ExitMethod not_met = Scan(offset + 1, end, labels);
return exit_method = ParallelExit(ExitMethod::AlwaysEnd, not_met);
}
}
case OpCode::Id::BRA: {
const u32 target = offset + instr.bra.GetBranchTarget();
labels.insert(target);
const ExitMethod no_jmp = Scan(offset + 1, end, labels);
const ExitMethod jmp = Scan(target, end, labels);
return exit_method = ParallelExit(no_jmp, jmp);
}
case OpCode::Id::SSY:
case OpCode::Id::PBK: {
// The SSY and PBK use a similar encoding as the BRA instruction.
UNIMPLEMENTED_IF_MSG(instr.bra.constant_buffer != 0,
"Constant buffer branching is not supported");
const u32 target = offset + instr.bra.GetBranchTarget();
labels.insert(target);
// Continue scanning for an exit method.
break;
}
}
}
return exit_method = ExitMethod::AlwaysReturn;
}
BasicBlock ShaderIR::DecodeRange(u32 begin, u32 end) {
BasicBlock basic_block;
for (u32 pc = begin; pc < (begin > end ? MAX_PROGRAM_LENGTH : end);) {
pc = DecodeInstr(basic_block, pc);
}
return std::move(basic_block);
}
u32 ShaderIR::DecodeInstr(BasicBlock& bb, u32 pc) {
// Ignore sched instructions when generating code.
if (IsSchedInstruction(pc, main_offset)) {
return pc + 1;
}
const Instruction instr = {program_code[pc]};
const auto opcode = OpCode::Decode(instr);
// Decoding failure
if (!opcode) {
UNIMPLEMENTED_MSG("Unhandled instruction: {0:x}", instr.value);
return pc + 1;
}
bb.push_back(
Comment(fmt::format("{}: {} (0x{:016x})", pc, opcode->get().GetName(), instr.value)));
using Tegra::Shader::Pred;
UNIMPLEMENTED_IF_MSG(instr.pred.full_pred == Pred::NeverExecute,
"NeverExecute predicate not implemented");
static const std::map<OpCode::Type, u32 (ShaderIR::*)(BasicBlock & code, u32 pc)> decoders = {
{OpCode::Type::Arithmetic, &ShaderIR::DecodeArithmetic},
{OpCode::Type::ArithmeticImmediate, &ShaderIR::DecodeArithmeticImmediate},
{OpCode::Type::Bfe, &ShaderIR::DecodeBfe},
{OpCode::Type::Bfi, &ShaderIR::DecodeBfi},
{OpCode::Type::Shift, &ShaderIR::DecodeShift},
{OpCode::Type::ArithmeticInteger, &ShaderIR::DecodeArithmeticInteger},
{OpCode::Type::ArithmeticIntegerImmediate, &ShaderIR::DecodeArithmeticIntegerImmediate},
{OpCode::Type::ArithmeticHalf, &ShaderIR::DecodeArithmeticHalf},
{OpCode::Type::ArithmeticHalfImmediate, &ShaderIR::DecodeArithmeticHalfImmediate},
{OpCode::Type::Ffma, &ShaderIR::DecodeFfma},
{OpCode::Type::Hfma2, &ShaderIR::DecodeHfma2},
{OpCode::Type::Conversion, &ShaderIR::DecodeConversion},
{OpCode::Type::Memory, &ShaderIR::DecodeMemory},
{OpCode::Type::FloatSetPredicate, &ShaderIR::DecodeFloatSetPredicate},
{OpCode::Type::IntegerSetPredicate, &ShaderIR::DecodeIntegerSetPredicate},
{OpCode::Type::HalfSetPredicate, &ShaderIR::DecodeHalfSetPredicate},
{OpCode::Type::PredicateSetRegister, &ShaderIR::DecodePredicateSetRegister},
{OpCode::Type::PredicateSetPredicate, &ShaderIR::DecodePredicateSetPredicate},
{OpCode::Type::RegisterSetPredicate, &ShaderIR::DecodeRegisterSetPredicate},
{OpCode::Type::FloatSet, &ShaderIR::DecodeFloatSet},
{OpCode::Type::IntegerSet, &ShaderIR::DecodeIntegerSet},
{OpCode::Type::HalfSet, &ShaderIR::DecodeHalfSet},
{OpCode::Type::Xmad, &ShaderIR::DecodeXmad},
};
std::vector<Node> code;
if (const auto decoder = decoders.find(opcode->get().GetType()); decoder != decoders.end()) {
pc = (this->*decoder->second)(code, pc);
} else {
pc = DecodeOther(code, pc);
}
// Some instructions (like SSY) don't have a predicate field, they are always unconditionally
// executed.
const bool can_be_predicated = OpCode::IsPredicatedInstruction(opcode->get().GetId());
const auto pred_index = static_cast<u32>(instr.pred.pred_index);
if (can_be_predicated && pred_index != static_cast<u32>(Pred::UnusedIndex)) {
bb.push_back(
Conditional(GetPredicate(pred_index, instr.negate_pred != 0), std::move(code)));
} else {
for (auto& node : code) {
bb.push_back(std::move(node));
}
}
return pc + 1;
}
} // namespace VideoCommon::Shader
