solidity/libyul/backends/wasm/BinaryTransform.cpp
Alex Beregszaszi 04cf4867fe [ewasm] Clean up opcodes/builtins in the binary encoder
Also make sure that `i32.drop/i64.drop` won't silently drop its arguments, as they may have side-effects.
2020-12-01 12:50:54 +00:00

724 lines
19 KiB
C++

/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
// SPDX-License-Identifier: GPL-3.0
/**
* Component that transforms internal Wasm representation to binary.
*/
#include <libyul/backends/wasm/BinaryTransform.h>
#include <libyul/Exceptions.h>
#include <libsolutil/CommonData.h>
#include <libsolutil/Visitor.h>
#include <libsolutil/LEB128.h>
#include <boost/range/adaptor/reversed.hpp>
#include <boost/range/adaptor/map.hpp>
#include <boost/range/adaptor/transformed.hpp>
using namespace std;
using namespace solidity;
using namespace solidity::yul;
using namespace solidity::yul::wasm;
using namespace solidity::util;
namespace
{
bytes toBytes(uint8_t _b)
{
return bytes(1, _b);
}
enum class LimitsKind: uint8_t
{
Min = 0x00,
MinMax = 0x01,
};
enum class Mutability: uint8_t
{
Const = 0x00,
Var = 0x01,
};
enum class Section: uint8_t
{
CUSTOM = 0x00,
TYPE = 0x01,
IMPORT = 0x02,
FUNCTION = 0x03,
MEMORY = 0x05,
GLOBAL = 0x06,
EXPORT = 0x07,
CODE = 0x0a
};
bytes toBytes(Section _s)
{
return toBytes(uint8_t(_s));
}
enum class ValueType: uint8_t
{
Void = 0x40,
Function = 0x60,
I64 = 0x7e,
I32 = 0x7f
};
bytes toBytes(ValueType _vt)
{
return toBytes(uint8_t(_vt));
}
ValueType toValueType(wasm::Type _type)
{
if (_type == wasm::Type::i32)
return ValueType::I32;
else if (_type == wasm::Type::i64)
return ValueType::I64;
else
yulAssert(false, "Invalid wasm variable type");
}
enum class Export: uint8_t
{
Function = 0x0,
Memory = 0x2
};
bytes toBytes(Export _export)
{
return toBytes(uint8_t(_export));
}
// NOTE: This is a subset of WebAssembly opcodes.
// Those available as a builtin are listed further down.
enum class Opcode: uint8_t
{
Block = 0x02,
Loop = 0x03,
If = 0x04,
Else = 0x05,
End = 0x0b,
Br = 0x0c,
BrIf = 0x0d,
BrTable = 0x0e, // Not used yet.
Return = 0x0f,
Call = 0x10,
CallIndirect = 0x11, // Not used yet.
LocalGet = 0x20,
LocalSet = 0x21,
LocalTee = 0x22, // Not used yet.
GlobalGet = 0x23,
GlobalSet = 0x24,
I32Const = 0x41,
I64Const = 0x42,
};
bytes toBytes(Opcode _o)
{
return toBytes(uint8_t(_o));
}
Opcode constOpcodeFor(ValueType _type)
{
if (_type == ValueType::I32)
return Opcode::I32Const;
else if (_type == ValueType::I64)
return Opcode::I64Const;
else
yulAssert(false, "Values of this type cannot be used with const opcode");
}
static map<string, uint8_t> const builtins = {
{"unreachable", 0x00},
{"nop", 0x01},
{"i32.drop", 0x1a},
{"i64.drop", 0x1a},
{"i32.select", 0x1b},
{"i64.select", 0x1b},
{"i32.load", 0x28},
{"i64.load", 0x29},
{"i32.load8_s", 0x2c},
{"i32.load8_u", 0x2d},
{"i32.load16_s", 0x2e},
{"i32.load16_u", 0x2f},
{"i64.load8_s", 0x30},
{"i64.load8_u", 0x31},
{"i64.load16_s", 0x32},
{"i64.load16_u", 0x33},
{"i64.load32_s", 0x34},
{"i64.load32_u", 0x35},
{"i32.store", 0x36},
{"i64.store", 0x37},
{"i32.store8", 0x3a},
{"i32.store16", 0x3b},
{"i64.store8", 0x3c},
{"i64.store16", 0x3d},
{"i64.store32", 0x3e},
{"memory.size", 0x3f},
{"memory.grow", 0x40},
{"i32.eqz", 0x45},
{"i32.eq", 0x46},
{"i32.ne", 0x47},
{"i32.lt_s", 0x48},
{"i32.lt_u", 0x49},
{"i32.gt_s", 0x4a},
{"i32.gt_u", 0x4b},
{"i32.le_s", 0x4c},
{"i32.le_u", 0x4d},
{"i32.ge_s", 0x4e},
{"i32.ge_u", 0x4f},
{"i64.eqz", 0x50},
{"i64.eq", 0x51},
{"i64.ne", 0x52},
{"i64.lt_s", 0x53},
{"i64.lt_u", 0x54},
{"i64.gt_s", 0x55},
{"i64.gt_u", 0x56},
{"i64.le_s", 0x57},
{"i64.le_u", 0x58},
{"i64.ge_s", 0x59},
{"i64.ge_u", 0x5a},
{"i32.clz", 0x67},
{"i32.ctz", 0x68},
{"i32.popcnt", 0x69},
{"i32.add", 0x6a},
{"i32.sub", 0x6b},
{"i32.mul", 0x6c},
{"i32.div_s", 0x6d},
{"i32.div_u", 0x6e},
{"i32.rem_s", 0x6f},
{"i32.rem_u", 0x70},
{"i32.and", 0x71},
{"i32.or", 0x72},
{"i32.xor", 0x73},
{"i32.shl", 0x74},
{"i32.shr_s", 0x75},
{"i32.shr_u", 0x76},
{"i32.rotl", 0x77},
{"i32.rotr", 0x78},
{"i64.clz", 0x79},
{"i64.ctz", 0x7a},
{"i64.popcnt", 0x7b},
{"i64.add", 0x7c},
{"i64.sub", 0x7d},
{"i64.mul", 0x7e},
{"i64.div_s", 0x7f},
{"i64.div_u", 0x80},
{"i64.rem_s", 0x81},
{"i64.rem_u", 0x82},
{"i64.and", 0x83},
{"i64.or", 0x84},
{"i64.xor", 0x85},
{"i64.shl", 0x86},
{"i64.shr_s", 0x87},
{"i64.shr_u", 0x88},
{"i64.rotl", 0x89},
{"i64.rotr", 0x8a},
{"i32.wrap_i64", 0xa7},
{"i64.extend_i32_s", 0xac},
{"i64.extend_i32_u", 0xad},
};
bytes prefixSize(bytes _data)
{
size_t size = _data.size();
return lebEncode(size) + move(_data);
}
bytes makeSection(Section _section, bytes _data)
{
return toBytes(_section) + prefixSize(move(_data));
}
/// This is a kind of run-length-encoding of local types.
vector<pair<size_t, ValueType>> groupLocalVariables(vector<VariableDeclaration> _localVariables)
{
vector<pair<size_t, ValueType>> localEntries;
size_t entrySize = 0;
ValueType entryType = ValueType::I32; // Any type would work here
for (VariableDeclaration const& localVariable: _localVariables)
{
ValueType variableType = toValueType(localVariable.type);
if (variableType != entryType)
{
if (entrySize > 0)
localEntries.emplace_back(entrySize, entryType);
entryType = variableType;
entrySize = 0;
}
++entrySize;
}
if (entrySize > 0)
localEntries.emplace_back(entrySize, entryType);
return localEntries;
}
}
bytes BinaryTransform::run(Module const& _module)
{
map<Type, vector<string>> const types = typeToFunctionMap(_module.imports, _module.functions);
map<string, size_t> const globalIDs = enumerateGlobals(_module);
map<string, size_t> const functionIDs = enumerateFunctions(_module);
map<string, size_t> const functionTypes = enumerateFunctionTypes(types);
yulAssert(globalIDs.size() == _module.globals.size(), "");
yulAssert(functionIDs.size() == _module.imports.size() + _module.functions.size(), "");
yulAssert(functionTypes.size() == functionIDs.size(), "");
yulAssert(functionTypes.size() >= types.size(), "");
bytes ret{0, 'a', 's', 'm'};
// version
ret += bytes{1, 0, 0, 0};
ret += typeSection(types);
ret += importSection(_module.imports, functionTypes);
ret += functionSection(_module.functions, functionTypes);
ret += memorySection();
ret += globalSection(_module.globals);
ret += exportSection(functionIDs);
map<string, pair<size_t, size_t>> subModulePosAndSize;
for (auto const& [name, module]: _module.subModules)
{
// TODO should we prefix and / or shorten the name?
bytes data = BinaryTransform::run(module);
size_t const length = data.size();
ret += customSection(name, move(data));
// Skip all the previous sections and the size field of this current custom section.
size_t const offset = ret.size() - length;
subModulePosAndSize[name] = {offset, length};
}
for (auto const& [name, data]: _module.customSections)
{
size_t const length = data.size();
ret += customSection(name, data);
// Skip all the previous sections and the size field of this current custom section.
size_t const offset = ret.size() - length;
subModulePosAndSize[name] = {offset, length};
}
BinaryTransform bt(
move(globalIDs),
move(functionIDs),
move(functionTypes),
move(subModulePosAndSize)
);
ret += bt.codeSection(_module.functions);
return ret;
}
bytes BinaryTransform::operator()(Literal const& _literal)
{
return std::visit(GenericVisitor{
[&](uint32_t _value) -> bytes { return toBytes(Opcode::I32Const) + lebEncodeSigned(static_cast<int32_t>(_value)); },
[&](uint64_t _value) -> bytes { return toBytes(Opcode::I64Const) + lebEncodeSigned(static_cast<int64_t>(_value)); },
}, _literal.value);
}
bytes BinaryTransform::operator()(StringLiteral const&)
{
// StringLiteral is a special AST element used for certain builtins.
// It is not mapped to actual WebAssembly, and should be processed in visit(BuiltinCall).
yulAssert(false, "");
}
bytes BinaryTransform::operator()(LocalVariable const& _variable)
{
return toBytes(Opcode::LocalGet) + lebEncode(m_locals.at(_variable.name));
}
bytes BinaryTransform::operator()(GlobalVariable const& _variable)
{
return toBytes(Opcode::GlobalGet) + lebEncode(m_globalIDs.at(_variable.name));
}
bytes BinaryTransform::operator()(BuiltinCall const& _call)
{
// We need to avoid visiting the arguments of `dataoffset` and `datasize` because
// they are references to object names that should not end up in the code.
if (_call.functionName == "dataoffset")
{
string name = get<StringLiteral>(_call.arguments.at(0)).value;
// TODO: support the case where name refers to the current object
yulAssert(m_subModulePosAndSize.count(name), "");
return toBytes(Opcode::I64Const) + lebEncodeSigned(static_cast<int64_t>(m_subModulePosAndSize.at(name).first));
}
else if (_call.functionName == "datasize")
{
string name = get<StringLiteral>(_call.arguments.at(0)).value;
// TODO: support the case where name refers to the current object
yulAssert(m_subModulePosAndSize.count(name), "");
return toBytes(Opcode::I64Const) + lebEncodeSigned(static_cast<int64_t>(m_subModulePosAndSize.at(name).second));
}
yulAssert(builtins.count(_call.functionName), "Builtin " + _call.functionName + " not found");
// NOTE: the dialect ensures we have the right amount of arguments
bytes args = visit(_call.arguments);
bytes ret = move(args) + toBytes(builtins.at(_call.functionName));
if (
_call.functionName.find(".load") != string::npos ||
_call.functionName.find(".store") != string::npos
)
// Alignment hint and offset. Interpreters ignore the alignment. JITs/AOTs can take it
// into account to generate more efficient code but if the hint is invalid it could
// actually be more expensive. It's best to hint at 1-byte alignment if we don't plan
// to control the memory layout accordingly.
ret += bytes{{0, 0}}; // 2^0 == 1-byte alignment
return ret;
}
bytes BinaryTransform::operator()(FunctionCall const& _call)
{
return visit(_call.arguments) + toBytes(Opcode::Call) + lebEncode(m_functionIDs.at(_call.functionName));
}
bytes BinaryTransform::operator()(LocalAssignment const& _assignment)
{
return
std::visit(*this, *_assignment.value) +
toBytes(Opcode::LocalSet) +
lebEncode(m_locals.at(_assignment.variableName));
}
bytes BinaryTransform::operator()(GlobalAssignment const& _assignment)
{
return
std::visit(*this, *_assignment.value) +
toBytes(Opcode::GlobalSet) +
lebEncode(m_globalIDs.at(_assignment.variableName));
}
bytes BinaryTransform::operator()(If const& _if)
{
bytes result =
std::visit(*this, *_if.condition) +
toBytes(Opcode::If) +
toBytes(ValueType::Void);
m_labels.emplace_back();
result += visit(_if.statements);
if (_if.elseStatements)
result += toBytes(Opcode::Else) + visit(*_if.elseStatements);
m_labels.pop_back();
result += toBytes(Opcode::End);
return result;
}
bytes BinaryTransform::operator()(Loop const& _loop)
{
bytes result = toBytes(Opcode::Loop) + toBytes(ValueType::Void);
m_labels.emplace_back(_loop.labelName);
result += visit(_loop.statements);
m_labels.pop_back();
result += toBytes(Opcode::End);
return result;
}
bytes BinaryTransform::operator()(Branch const& _branch)
{
return toBytes(Opcode::Br) + encodeLabelIdx(_branch.label.name);
}
bytes BinaryTransform::operator()(BranchIf const& _branchIf)
{
bytes result = std::visit(*this, *_branchIf.condition);
result += toBytes(Opcode::BrIf) + encodeLabelIdx(_branchIf.label.name);
return result;
}
bytes BinaryTransform::operator()(Return const&)
{
// Note that this does not work if the function returns a value.
return toBytes(Opcode::Return);
}
bytes BinaryTransform::operator()(Block const& _block)
{
m_labels.emplace_back(_block.labelName);
bytes result =
toBytes(Opcode::Block) +
toBytes(ValueType::Void) +
visit(_block.statements) +
toBytes(Opcode::End);
m_labels.pop_back();
return result;
}
bytes BinaryTransform::operator()(FunctionDefinition const& _function)
{
bytes ret;
vector<pair<size_t, ValueType>> localEntries = groupLocalVariables(_function.locals);
ret += lebEncode(localEntries.size());
for (pair<size_t, ValueType> const& entry: localEntries)
{
ret += lebEncode(entry.first);
ret += toBytes(entry.second);
}
m_locals.clear();
size_t varIdx = 0;
for (size_t i = 0; i < _function.parameters.size(); ++i)
m_locals[_function.parameters[i].name] = varIdx++;
for (size_t i = 0; i < _function.locals.size(); ++i)
m_locals[_function.locals[i].variableName] = varIdx++;
yulAssert(m_labels.empty(), "Stray labels.");
ret += visit(_function.body);
ret += toBytes(Opcode::End);
yulAssert(m_labels.empty(), "Stray labels.");
return prefixSize(move(ret));
}
BinaryTransform::Type BinaryTransform::typeOf(FunctionImport const& _import)
{
return {
encodeTypes(_import.paramTypes),
encodeTypes(_import.returnType ? vector<wasm::Type>(1, *_import.returnType) : vector<wasm::Type>())
};
}
BinaryTransform::Type BinaryTransform::typeOf(FunctionDefinition const& _funDef)
{
return {
encodeTypes(_funDef.parameters),
encodeTypes(_funDef.returnType ? vector<wasm::Type>(1, *_funDef.returnType) : vector<wasm::Type>())
};
}
uint8_t BinaryTransform::encodeType(wasm::Type _type)
{
return uint8_t(toValueType(_type));
}
vector<uint8_t> BinaryTransform::encodeTypes(vector<wasm::Type> const& _types)
{
vector<uint8_t> result;
for (wasm::Type t: _types)
result.emplace_back(encodeType(t));
return result;
}
vector<uint8_t> BinaryTransform::encodeTypes(wasm::TypedNameList const& _typedNameList)
{
vector<uint8_t> result;
for (TypedName const& typedName: _typedNameList)
result.emplace_back(encodeType(typedName.type));
return result;
}
map<BinaryTransform::Type, vector<string>> BinaryTransform::typeToFunctionMap(
vector<wasm::FunctionImport> const& _imports,
vector<wasm::FunctionDefinition> const& _functions
)
{
map<Type, vector<string>> types;
for (auto const& import: _imports)
types[typeOf(import)].emplace_back(import.internalName);
for (auto const& fun: _functions)
types[typeOf(fun)].emplace_back(fun.name);
return types;
}
map<string, size_t> BinaryTransform::enumerateGlobals(Module const& _module)
{
map<string, size_t> globals;
for (size_t i = 0; i < _module.globals.size(); ++i)
globals[_module.globals[i].variableName] = i;
return globals;
}
map<string, size_t> BinaryTransform::enumerateFunctions(Module const& _module)
{
map<string, size_t> functions;
size_t funID = 0;
for (FunctionImport const& fun: _module.imports)
functions[fun.internalName] = funID++;
for (FunctionDefinition const& fun: _module.functions)
functions[fun.name] = funID++;
return functions;
}
map<string, size_t> BinaryTransform::enumerateFunctionTypes(map<Type, vector<string>> const& _typeToFunctionMap)
{
map<string, size_t> functionTypes;
size_t typeID = 0;
for (vector<string> const& funNames: _typeToFunctionMap | boost::adaptors::map_values)
{
for (string const& name: funNames)
functionTypes[name] = typeID;
++typeID;
}
return functionTypes;
}
bytes BinaryTransform::typeSection(map<BinaryTransform::Type, vector<string>> const& _typeToFunctionMap)
{
bytes result;
size_t index = 0;
for (Type const& type: _typeToFunctionMap | boost::adaptors::map_keys)
{
result += toBytes(ValueType::Function);
result += lebEncode(type.first.size()) + type.first;
result += lebEncode(type.second.size()) + type.second;
index++;
}
return makeSection(Section::TYPE, lebEncode(index) + move(result));
}
bytes BinaryTransform::importSection(
vector<FunctionImport> const& _imports,
map<string, size_t> const& _functionTypes
)
{
bytes result = lebEncode(_imports.size());
for (FunctionImport const& import: _imports)
{
uint8_t importKind = 0; // function
result +=
encodeName(import.module) +
encodeName(import.externalName) +
toBytes(importKind) +
lebEncode(_functionTypes.at(import.internalName));
}
return makeSection(Section::IMPORT, move(result));
}
bytes BinaryTransform::functionSection(
vector<FunctionDefinition> const& _functions,
map<string, size_t> const& _functionTypes
)
{
bytes result = lebEncode(_functions.size());
for (auto const& fun: _functions)
result += lebEncode(_functionTypes.at(fun.name));
return makeSection(Section::FUNCTION, move(result));
}
bytes BinaryTransform::memorySection()
{
bytes result = lebEncode(1);
result.push_back(static_cast<uint8_t>(LimitsKind::Min));
result.push_back(1); // initial length
return makeSection(Section::MEMORY, move(result));
}
bytes BinaryTransform::globalSection(vector<wasm::GlobalVariableDeclaration> const& _globals)
{
bytes result = lebEncode(_globals.size());
for (wasm::GlobalVariableDeclaration const& global: _globals)
{
ValueType globalType = toValueType(global.type);
result +=
toBytes(globalType) +
lebEncode(static_cast<uint8_t>(Mutability::Var)) +
toBytes(constOpcodeFor(globalType)) +
lebEncodeSigned(0) +
toBytes(Opcode::End);
}
return makeSection(Section::GLOBAL, move(result));
}
bytes BinaryTransform::exportSection(map<string, size_t> const& _functionIDs)
{
bool hasMain = _functionIDs.count("main");
bytes result = lebEncode(hasMain ? 2 : 1);
result += encodeName("memory") + toBytes(Export::Memory) + lebEncode(0);
if (hasMain)
result += encodeName("main") + toBytes(Export::Function) + lebEncode(_functionIDs.at("main"));
return makeSection(Section::EXPORT, move(result));
}
bytes BinaryTransform::customSection(string const& _name, bytes _data)
{
bytes result = encodeName(_name) + move(_data);
return makeSection(Section::CUSTOM, move(result));
}
bytes BinaryTransform::codeSection(vector<wasm::FunctionDefinition> const& _functions)
{
bytes result = lebEncode(_functions.size());
for (FunctionDefinition const& fun: _functions)
result += (*this)(fun);
return makeSection(Section::CODE, move(result));
}
bytes BinaryTransform::visit(vector<Expression> const& _expressions)
{
bytes result;
for (auto const& expr: _expressions)
result += std::visit(*this, expr);
return result;
}
bytes BinaryTransform::visitReversed(vector<Expression> const& _expressions)
{
bytes result;
for (auto const& expr: _expressions | boost::adaptors::reversed)
result += std::visit(*this, expr);
return result;
}
bytes BinaryTransform::encodeLabelIdx(string const& _label) const
{
yulAssert(!_label.empty(), "Empty label.");
size_t depth = 0;
for (string const& label: m_labels | boost::adaptors::reversed)
if (label == _label)
return lebEncode(depth);
else
++depth;
yulAssert(false, "Label not found.");
}
bytes BinaryTransform::encodeName(string const& _name)
{
// UTF-8 is allowed here by the Wasm spec, but since all names here should stem from
// Solidity or Yul identifiers or similar, non-ascii characters ending up here
// is a very bad sign.
for (char c: _name)
yulAssert(uint8_t(c) <= 0x7f, "Non-ascii character found.");
return lebEncode(_name.size()) + asBytes(_name);
}