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// SPDX-License-Identifier: GPL-3.0-or-later
#include "rcc/MC/MCFixup.h"
#include <algorithm>
#include <array>
#include <cstdint>
#include <limits>
#include <utility>
#include <vector>
namespace rcc::mc {
namespace {
[[nodiscard]] Expected<std::int64_t> checkedAdd(std::int64_t Left, std::int64_t Right) {
std::int64_t Result = 0;
if (__builtin_add_overflow(Left, Right, &Result))
return makeUnexpected(ErrorCode::RelocationFailed, "MC expression addition overflows");
return Result;
}
[[nodiscard]] Expected<std::int64_t> checkedSubtract(std::int64_t Left, std::int64_t Right) {
std::int64_t Result = 0;
if (__builtin_sub_overflow(Left, Right, &Result))
return makeUnexpected(ErrorCode::RelocationFailed, "MC expression subtraction overflows");
return Result;
}
[[nodiscard]] Expected<MCValue> combineLinearValues(const MCValue &Left, const MCValue &Right,
bool SubtractRight) {
struct SymbolTerm final {
MCSymbolRef Symbol;
int Coefficient = 0;
};
std::vector<SymbolTerm> Terms;
const auto AddTerm = [&Terms](const MCSymbolRef &Symbol, int Coefficient) -> Expected<void> {
if (!Symbol)
return {};
const auto Position = std::ranges::find(Terms, Symbol, &SymbolTerm::Symbol);
if (Position == Terms.end()) {
Terms.push_back(SymbolTerm{.Symbol = Symbol, .Coefficient = Coefficient});
return {};
}
Position->Coefficient += Coefficient;
if (Position->Coefficient < -1 || Position->Coefficient > 1) {
return makeUnexpected(ErrorCode::RelocationFailed,
"MC expression has a symbol coefficient outside -1 to 1");
}
if (Position->Coefficient == 0)
Terms.erase(Position);
return {};
};
for (const auto &[Symbol, Coefficient] : std::array<std::pair<MCSymbolRef, int>, 4>{
std::pair{Left.AddSymbol, 1},
std::pair{Left.SubtractSymbol, -1},
std::pair{Right.AddSymbol, SubtractRight ? -1 : 1},
std::pair{Right.SubtractSymbol, SubtractRight ? 1 : -1},
}) {
auto Added = AddTerm(Symbol, Coefficient);
if (!Added)
return std::unexpected(Added.error());
}
MCValue Result;
for (const SymbolTerm &Term : Terms) {
MCSymbolRef &Destination = Term.Coefficient > 0 ? Result.AddSymbol : Result.SubtractSymbol;
if (Destination) {
return makeUnexpected(ErrorCode::RelocationFailed,
"MC expression contains more than one symbol with the same sign");
}
Destination = Term.Symbol;
}
auto Addend = SubtractRight ? checkedSubtract(Left.Addend, Right.Addend)
: checkedAdd(Left.Addend, Right.Addend);
if (!Addend)
return std::unexpected(Addend.error());
Result.Addend = *Addend;
return Result;
}
[[nodiscard]] Expected<MCValue> evaluate(const MCExpr &Expression, std::size_t Depth) {
if (Depth > 256)
return makeUnexpected(ErrorCode::RelocationFailed, "MC expression exceeds its depth limit");
switch (Expression.kind()) {
case MCExpr::Kind::Constant:
return MCValue{.AddSymbol = {},
.SubtractSymbol = {},
.Addend = *Expression.getIf<std::int64_t>(),
.TargetKind = 0};
case MCExpr::Kind::SymbolRef:
return MCValue{.AddSymbol = Expression.getIf<MCSymbolRefExpr>()->Symbol,
.SubtractSymbol = {},
.Addend = 0,
.TargetKind = 0};
case MCExpr::Kind::Target: {
const auto &Target = *Expression.getIf<MCTargetExpr>();
auto Result = evaluate(*Target.Operand, Depth + 1);
if (!Result)
return std::unexpected(Result.error());
if (Result->TargetKind != 0) {
return makeUnexpected(ErrorCode::RelocationFailed,
"nested target MC expressions are not relocatable");
}
Result->TargetKind = Target.Kind;
return Result;
}
case MCExpr::Kind::Unary: {
const auto &Unary = *Expression.getIf<MCUnaryExpr>();
auto Operand = evaluate(*Unary.Operand, Depth + 1);
if (!Operand)
return std::unexpected(Operand.error());
if (Unary.Operator == MCUnaryOperator::Plus)
return Operand;
if (Unary.Operator == MCUnaryOperator::Minus && Operand->isAbsolute()) {
if (Operand->Addend == std::numeric_limits<std::int64_t>::min()) {
return makeUnexpected(ErrorCode::RelocationFailed, "MC expression negation overflows");
}
Operand->Addend = -Operand->Addend;
return Operand;
}
const auto Absolute = Expression.evaluateAbsolute();
if (!Absolute) {
return makeUnexpected(ErrorCode::RelocationFailed,
"symbolic unary MC expression is not relocatable");
}
return MCValue{.AddSymbol = {}, .SubtractSymbol = {}, .Addend = *Absolute, .TargetKind = 0};
}
case MCExpr::Kind::Binary: {
const auto &Binary = *Expression.getIf<MCBinaryExpr>();
if (Binary.Operator != MCBinaryOperator::Add && Binary.Operator != MCBinaryOperator::Subtract) {
const auto Absolute = Expression.evaluateAbsolute();
if (!Absolute) {
return makeUnexpected(ErrorCode::RelocationFailed,
"symbolic binary MC expression is not relocatable");
}
return MCValue{.AddSymbol = {}, .SubtractSymbol = {}, .Addend = *Absolute, .TargetKind = 0};
}
auto Left = evaluate(*Binary.Left, Depth + 1);
auto Right = evaluate(*Binary.Right, Depth + 1);
if (!Left)
return std::unexpected(Left.error());
if (!Right)
return std::unexpected(Right.error());
if (Left->TargetKind != 0 || Right->TargetKind != 0) {
return makeUnexpected(ErrorCode::RelocationFailed,
"target MC expression cannot participate in outer arithmetic");
}
return combineLinearValues(*Left, *Right, Binary.Operator == MCBinaryOperator::Subtract);
}
}
return makeUnexpected(ErrorCode::InternalError, "MC expression has an invalid kind");
}
} // namespace
Expected<void> MCFixup::verify() const {
if (Kind == fixup_kind::None)
return makeUnexpected(ErrorCode::InvalidArgument, "MC fixup has no kind");
if (!Value)
return makeUnexpected(ErrorCode::InvalidArgument, "MC fixup has no value expression");
auto Verification = Value->verify();
if (!Verification)
return std::unexpected(Verification.error());
return {};
}
Expected<MCValue> evaluateAsRelocatable(const MCExpr &Expression) {
auto Verification = Expression.verify();
if (!Verification)
return std::unexpected(Verification.error());
return evaluate(Expression, 0);
}
} // namespace rcc::mc
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