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llvm-project/llvm/lib/MC/MCExpr.cpp
Fangrui Song 69d0078f16 MC: Generate relocation for a branch crossing linker-relaxable FT_Align fragment 
"Encode FT_Align in fragment's variable-size tail" or a neighbor change
caused a regression that was similar to the root cause of
ab0931b6389838cb5d7d11914063a1ddd84102f0
(See the new test (.text3 with a call at the start"))

For a FT_Align fragment, the offset between location A (with offset <=
FixedSize) and B (offset == FixedSize+VarSize) cannot be resolved.

In addition, delete unneeded condition `F->isLinkerRelaxable()`.

LoongArch linker relaxation is largely under-tested, but update it as well.
2025-07-26 21:19:48 -07:00

752 lines
26 KiB
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//===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCExpr.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
using namespace llvm;
#define DEBUG_TYPE "mcexpr"
namespace {
namespace stats {
STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
} // end namespace stats
} // end anonymous namespace
static int getPrecedence(MCBinaryExpr::Opcode Op) {
switch (Op) {
case MCBinaryExpr::Add:
case MCBinaryExpr::Sub:
return 1;
default:
return 0;
}
}
// VariantKind printing and formatting utilize MAI. operator<< (dump and some
// target code) specifies MAI as nullptr and should be avoided when MAI is
// needed.
void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI,
int SurroundingPrec) const {
constexpr int MaxPrec = 9;
switch (getKind()) {
case MCExpr::Target:
return cast<MCTargetExpr>(this)->printImpl(OS, MAI);
case MCExpr::Constant: {
auto Value = cast<MCConstantExpr>(*this).getValue();
auto PrintInHex = cast<MCConstantExpr>(*this).useHexFormat();
auto SizeInBytes = cast<MCConstantExpr>(*this).getSizeInBytes();
if (Value < 0 && MAI && !MAI->supportsSignedData())
PrintInHex = true;
if (PrintInHex)
switch (SizeInBytes) {
default:
OS << "0x" << Twine::utohexstr(Value);
break;
case 1:
OS << format("0x%02" PRIx64, Value);
break;
case 2:
OS << format("0x%04" PRIx64, Value);
break;
case 4:
OS << format("0x%08" PRIx64, Value);
break;
case 8:
OS << format("0x%016" PRIx64, Value);
break;
}
else
OS << Value;
return;
}
case MCExpr::SymbolRef: {
const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this);
const MCSymbol &Sym = SRE.getSymbol();
Sym.print(OS, MAI);
const MCSymbolRefExpr::VariantKind Kind = SRE.getKind();
if (Kind) {
if (!MAI) // should only be used by dump()
OS << "@<variant " << Kind << '>';
else if (MAI->useParensForSpecifier()) // ARM
OS << '(' << MAI->getSpecifierName(Kind) << ')';
else
OS << '@' << MAI->getSpecifierName(Kind);
}
return;
}
case MCExpr::Unary: {
const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
switch (UE.getOpcode()) {
case MCUnaryExpr::LNot: OS << '!'; break;
case MCUnaryExpr::Minus: OS << '-'; break;
case MCUnaryExpr::Not: OS << '~'; break;
case MCUnaryExpr::Plus: OS << '+'; break;
}
UE.getSubExpr()->print(OS, MAI, MaxPrec);
return;
}
case MCExpr::Binary: {
const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
// We want to avoid redundant parentheses for relocatable expressions like
// a-b+c.
//
// Print '(' if the current operator has lower precedence than the
// surrounding operator, or if the surrounding operator's precedence is
// unknown (set to HighPrecedence).
int Prec = getPrecedence(BE.getOpcode());
bool Paren = Prec < SurroundingPrec;
if (Paren)
OS << '(';
// Many operators' precedence is different from C. Set the precedence to
// HighPrecedence for unknown operators.
int SubPrec = Prec ? Prec : MaxPrec;
BE.getLHS()->print(OS, MAI, SubPrec);
switch (BE.getOpcode()) {
case MCBinaryExpr::Add:
// Print "X-42" instead of "X+-42".
if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
if (RHSC->getValue() < 0) {
OS << RHSC->getValue();
if (Paren)
OS << ')';
return;
}
}
OS << '+';
break;
case MCBinaryExpr::AShr: OS << ">>"; break;
case MCBinaryExpr::And: OS << '&'; break;
case MCBinaryExpr::Div: OS << '/'; break;
case MCBinaryExpr::EQ: OS << "=="; break;
case MCBinaryExpr::GT: OS << '>'; break;
case MCBinaryExpr::GTE: OS << ">="; break;
case MCBinaryExpr::LAnd: OS << "&&"; break;
case MCBinaryExpr::LOr: OS << "||"; break;
case MCBinaryExpr::LShr: OS << ">>"; break;
case MCBinaryExpr::LT: OS << '<'; break;
case MCBinaryExpr::LTE: OS << "<="; break;
case MCBinaryExpr::Mod: OS << '%'; break;
case MCBinaryExpr::Mul: OS << '*'; break;
case MCBinaryExpr::NE: OS << "!="; break;
case MCBinaryExpr::Or: OS << '|'; break;
case MCBinaryExpr::OrNot: OS << '!'; break;
case MCBinaryExpr::Shl: OS << "<<"; break;
case MCBinaryExpr::Sub: OS << '-'; break;
case MCBinaryExpr::Xor: OS << '^'; break;
}
BE.getRHS()->print(OS, MAI, SubPrec + 1);
if (Paren)
OS << ')';
return;
}
case MCExpr::Specifier: {
auto &SE = cast<MCSpecifierExpr>(*this);
if (MAI)
return MAI->printSpecifierExpr(OS, SE);
// Used by dump features like -show-inst. Regular MCAsmStreamer output must
// set MAI.
OS << "specifier(" << SE.getSpecifier() << ',';
SE.getSubExpr()->print(OS, nullptr);
OS << ')';
return;
}
}
llvm_unreachable("Invalid expression kind!");
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void MCExpr::dump() const {
print(dbgs(), nullptr);
dbgs() << '\n';
}
#endif
/* *** */
const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS,
const MCExpr *RHS, MCContext &Ctx,
SMLoc Loc) {
return new (Ctx) MCBinaryExpr(Opc, LHS, RHS, Loc);
}
const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr,
MCContext &Ctx, SMLoc Loc) {
return new (Ctx) MCUnaryExpr(Opc, Expr, Loc);
}
const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx,
bool PrintInHex,
unsigned SizeInBytes) {
return new (Ctx) MCConstantExpr(Value, PrintInHex, SizeInBytes);
}
/* *** */
MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, Spec specifier,
const MCAsmInfo *MAI, SMLoc Loc)
: MCExpr(MCExpr::SymbolRef, Loc, specifier), Symbol(Symbol) {
assert(Symbol);
}
const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym,
uint16_t specifier,
MCContext &Ctx, SMLoc Loc) {
return new (Ctx) MCSymbolRefExpr(Sym, specifier, Ctx.getAsmInfo(), Loc);
}
/* *** */
void MCTargetExpr::anchor() {}
/* *** */
bool MCExpr::evaluateAsAbsolute(int64_t &Res) const {
return evaluateAsAbsolute(Res, nullptr, false);
}
bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
return evaluateAsAbsolute(Res, &Asm, false);
}
bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm) const {
return evaluateAsAbsolute(Res, Asm, false);
}
bool MCExpr::evaluateKnownAbsolute(int64_t &Res, const MCAssembler &Asm) const {
return evaluateAsAbsolute(Res, &Asm, true);
}
bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
bool InSet) const {
MCValue Value;
// Fast path constants.
if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
Res = CE->getValue();
return true;
}
bool IsRelocatable = evaluateAsRelocatableImpl(Value, Asm, InSet);
Res = Value.getConstant();
// Value with RefKind (e.g. %hi(0xdeadbeef) in MIPS) is not considered
// absolute (the value is unknown at parse time), even if it might be resolved
// by evaluateFixup.
return IsRelocatable && Value.isAbsolute() && Value.getSpecifier() == 0;
}
/// Helper method for \see EvaluateSymbolAdd().
static void attemptToFoldSymbolOffsetDifference(const MCAssembler *Asm,
bool InSet, const MCSymbol *&A,
const MCSymbol *&B,
int64_t &Addend) {
if (!A || !B)
return;
const MCSymbol &SA = *A, &SB = *B;
if (SA.isUndefined() || SB.isUndefined())
return;
if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(SA, SB, InSet))
return;
auto FinalizeFolding = [&]() {
// Pointers to Thumb symbols need to have their low-bit set to allow
// for interworking.
if (Asm->isThumbFunc(&SA))
Addend |= 1;
// Clear the symbol expr pointers to indicate we have folded these
// operands.
A = B = nullptr;
};
const MCFragment *FA = SA.getFragment();
const MCFragment *FB = SB.getFragment();
const MCSection &SecA = *FA->getParent();
const MCSection &SecB = *FB->getParent();
if (&SecA != &SecB)
return;
// When layout is available, we can generally compute the difference using the
// getSymbolOffset path, which also avoids the possible slow fragment walk.
// However, linker relaxation may cause incorrect fold of A-B if A and B are
// separated by a linker-relaxable fragment. If the section contains
// linker-relaxable instruction and InSet is false (not expressions in
// directive like .size/.fill), disable the fast path.
bool Layout = Asm->hasLayout();
if (Layout && (InSet || !SecA.isLinkerRelaxable())) {
// If both symbols are in the same fragment, return the difference of their
// offsets. canGetFragmentOffset(FA) may be false.
if (FA == FB && !SA.isVariable() && !SB.isVariable()) {
Addend += SA.getOffset() - SB.getOffset();
return FinalizeFolding();
}
// Eagerly evaluate when layout is finalized.
Addend += Asm->getSymbolOffset(SA) - Asm->getSymbolOffset(SB);
FinalizeFolding();
} else {
// When layout is not finalized, our ability to resolve differences between
// symbols is limited to specific cases where the fragments between two
// symbols (including the fragments the symbols are defined in) are
// fixed-size fragments so the difference can be calculated. For example,
// this is important when the Subtarget is changed and a new MCFragment
// is created in the case of foo: instr; .arch_extension ext; instr .if . -
// foo.
if (SA.isVariable() || SB.isVariable())
return;
// Try to find a constant displacement from FA to FB, add the displacement
// between the offset in FA of SA and the offset in FB of SB.
bool Reverse = false;
if (FA == FB)
Reverse = SA.getOffset() < SB.getOffset();
else
Reverse = FA->getLayoutOrder() < FB->getLayoutOrder();
uint64_t SAOffset = SA.getOffset(), SBOffset = SB.getOffset();
int64_t Displacement = SA.getOffset() - SB.getOffset();
if (Reverse) {
std::swap(FA, FB);
std::swap(SAOffset, SBOffset);
Displacement *= -1;
}
// Track whether B is before a relaxable instruction/alignment and whether A
// is after a relaxable instruction/alignment. If SA and SB are separated by
// a linker-relaxable instruction/alignment, the difference cannot be
// resolved as it may be changed by the linker.
bool BBeforeRelax = false, AAfterRelax = false;
for (auto F = FB; F; F = F->getNext()) {
if (F && F->isLinkerRelaxable()) {
if (&*F != FB || SBOffset != F->getSize())
BBeforeRelax = true;
if (&*F != FA || SAOffset == F->getSize())
AAfterRelax = true;
if (BBeforeRelax && AAfterRelax)
return;
}
if (&*F == FA) {
// If FA and FB belong to the same subsection, the loop will find FA and
// we can resolve the difference.
Addend += Reverse ? -Displacement : Displacement;
FinalizeFolding();
return;
}
int64_t Num;
if (F->getKind() == MCFragment::FT_Data) {
Displacement += F->getFixedSize();
} else if ((F->getKind() == MCFragment::FT_Relaxable ||
F->getKind() == MCFragment::FT_Align) &&
Asm->hasFinalLayout()) {
// Before finishLayout, a relaxable fragment's size is indeterminate.
// After layout, during relocation generation, it can be treated as a
// data fragment.
Displacement += F->getSize();
} else if (auto *FF = dyn_cast<MCFillFragment>(F);
FF && FF->getNumValues().evaluateAsAbsolute(Num)) {
Displacement += Num * FF->getValueSize();
} else {
return;
}
}
}
}
// Evaluate the sum of two relocatable expressions.
//
// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
//
// This routine attempts to aggressively fold the operands such that the result
// is representable in an MCValue, but may not always succeed.
//
// LHS_A and RHS_A might have relocation specifiers while LHS_B and RHS_B
// cannot have specifiers.
//
// \returns True on success, false if the result is not representable in an
// MCValue.
// NOTE: This function can be used before layout is done (see the object
// streamer for example) and having the Asm argument lets us avoid relaxations
// early.
bool MCExpr::evaluateSymbolicAdd(const MCAssembler *Asm, bool InSet,
const MCValue &LHS, const MCValue &RHS,
MCValue &Res) {
const MCSymbol *LHS_A = LHS.getAddSym();
const MCSymbol *LHS_B = LHS.getSubSym();
int64_t LHS_Cst = LHS.getConstant();
const MCSymbol *RHS_A = RHS.getAddSym();
const MCSymbol *RHS_B = RHS.getSubSym();
int64_t RHS_Cst = RHS.getConstant();
// Fold the result constant immediately.
int64_t Result_Cst = LHS_Cst + RHS_Cst;
// If we have a layout, we can fold resolved differences.
if (Asm && !LHS.getSpecifier() && !RHS.getSpecifier()) {
// While LHS_A-LHS_B and RHS_A-RHS_B from recursive calls have already been
// folded, reassociating terms in
// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
// might bring more opportunities.
if (LHS_A && RHS_B) {
attemptToFoldSymbolOffsetDifference(Asm, InSet, LHS_A, RHS_B, Result_Cst);
}
if (RHS_A && LHS_B) {
attemptToFoldSymbolOffsetDifference(Asm, InSet, RHS_A, LHS_B, Result_Cst);
}
}
// We can't represent the addition or subtraction of two symbols.
if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
return false;
// At this point, we have at most one additive symbol and one subtractive
// symbol -- find them.
auto *A = LHS_A ? LHS_A : RHS_A;
auto *B = LHS_B ? LHS_B : RHS_B;
auto Spec = LHS.getSpecifier();
if (!Spec)
Spec = RHS.getSpecifier();
Res = MCValue::get(A, B, Result_Cst, Spec);
return true;
}
bool MCExpr::evaluateAsRelocatable(MCValue &Res, const MCAssembler *Asm) const {
return evaluateAsRelocatableImpl(Res, Asm, false);
}
bool MCExpr::evaluateAsValue(MCValue &Res, const MCAssembler &Asm) const {
return evaluateAsRelocatableImpl(Res, &Asm, true);
}
bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
bool InSet) const {
++stats::MCExprEvaluate;
switch (getKind()) {
case Target:
return cast<MCTargetExpr>(this)->evaluateAsRelocatableImpl(Res, Asm);
case Constant:
Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
return true;
case SymbolRef: {
const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
MCSymbol &Sym = const_cast<MCSymbol &>(SRE->getSymbol());
const auto Kind = SRE->getKind();
bool Layout = Asm && Asm->hasLayout();
// If the symbol is equated, resolve the inner expression.
// However, when two IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY symbols reference
// each other, we retain the equated symbol to avoid a cyclic definition
// error.
if (Sym.isResolving()) {
if (Asm && Asm->hasFinalLayout()) {
Asm->getContext().reportError(
Sym.getVariableValue()->getLoc(),
"cyclic dependency detected for symbol '" + Sym.getName() + "'");
Sym.setVariableValue(MCConstantExpr::create(0, Asm->getContext()));
}
return false;
}
if (Sym.isVariable() && (Kind == 0 || Layout) && !Sym.isWeakExternal()) {
Sym.setIsResolving(true);
auto _ = make_scope_exit([&] { Sym.setIsResolving(false); });
bool IsMachO =
Asm && Asm->getContext().getAsmInfo()->hasSubsectionsViaSymbols();
if (!Sym.getVariableValue()->evaluateAsRelocatableImpl(Res, Asm,
InSet || IsMachO))
return false;
// When generating relocations, if Sym resolves to a symbol relative to a
// section, relocations are generated against Sym. Treat label differences
// as constants.
auto *A = Res.getAddSym();
auto *B = Res.getSubSym();
if (InSet || !(A && !B && A->isInSection())) {
if (Kind) {
if (Res.isAbsolute()) {
Res = MCValue::get(&Sym, nullptr, 0, Kind);
return true;
}
// If the reference has a variant kind, we can only handle expressions
// which evaluate exactly to a single unadorned symbol. Attach the
// original VariantKind to SymA of the result.
if (Res.getSpecifier() || !Res.getAddSym() || Res.getSubSym() ||
Res.getConstant())
return false;
Res.Specifier = Kind;
}
if (!IsMachO)
return true;
// FIXME: This is small hack. Given
// a = b + 4
// .long a
// the OS X assembler will completely drop the 4. We should probably
// include it in the relocation or produce an error if that is not
// possible.
// Allow constant expressions.
if (!A && !B)
return true;
// Allows aliases with zero offset.
if (Res.getConstant() == 0 && (!A || !B))
return true;
}
}
Res = MCValue::get(&Sym, nullptr, 0, Kind);
return true;
}
case Unary: {
const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
MCValue Value;
if (!AUE->getSubExpr()->evaluateAsRelocatableImpl(Value, Asm, InSet))
return false;
switch (AUE->getOpcode()) {
case MCUnaryExpr::LNot:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(!Value.getConstant());
break;
case MCUnaryExpr::Minus:
/// -(a - b + const) ==> (b - a - const)
if (Value.getAddSym() && !Value.getSubSym())
return false;
// The cast avoids undefined behavior if the constant is INT64_MIN.
Res = MCValue::get(Value.getSubSym(), Value.getAddSym(),
-(uint64_t)Value.getConstant());
break;
case MCUnaryExpr::Not:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(~Value.getConstant());
break;
case MCUnaryExpr::Plus:
Res = Value;
break;
}
return true;
}
case Binary: {
const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
MCValue LHSValue, RHSValue;
if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, InSet) ||
!ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, InSet)) {
// Check if both are Target Expressions, see if we can compare them.
if (const MCTargetExpr *L = dyn_cast<MCTargetExpr>(ABE->getLHS())) {
if (const MCTargetExpr *R = dyn_cast<MCTargetExpr>(ABE->getRHS())) {
switch (ABE->getOpcode()) {
case MCBinaryExpr::EQ:
Res = MCValue::get(L->isEqualTo(R) ? -1 : 0);
return true;
case MCBinaryExpr::NE:
Res = MCValue::get(L->isEqualTo(R) ? 0 : -1);
return true;
default:
break;
}
}
}
return false;
}
// We only support a few operations on non-constant expressions, handle
// those first.
auto Op = ABE->getOpcode();
int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
switch (Op) {
default:
return false;
case MCBinaryExpr::Add:
case MCBinaryExpr::Sub:
if (Op == MCBinaryExpr::Sub) {
std::swap(RHSValue.SymA, RHSValue.SymB);
RHSValue.Cst = -(uint64_t)RHSValue.Cst;
}
if (RHSValue.isAbsolute()) {
LHSValue.Cst += RHSValue.Cst;
Res = LHSValue;
return true;
}
if (LHSValue.isAbsolute()) {
RHSValue.Cst += LHSValue.Cst;
Res = RHSValue;
return true;
}
if (LHSValue.SymB && LHSValue.Specifier)
return false;
if (RHSValue.SymB && RHSValue.Specifier)
return false;
return evaluateSymbolicAdd(Asm, InSet, LHSValue, RHSValue, Res);
}
}
// FIXME: We need target hooks for the evaluation. It may be limited in
// width, and gas defines the result of comparisons differently from
// Apple as.
int64_t Result = 0;
switch (Op) {
case MCBinaryExpr::AShr: Result = LHS >> RHS; break;
case MCBinaryExpr::Add: Result = LHS + RHS; break;
case MCBinaryExpr::And: Result = LHS & RHS; break;
case MCBinaryExpr::Div:
case MCBinaryExpr::Mod:
// Handle division by zero. gas just emits a warning and keeps going,
// we try to be stricter.
// FIXME: Currently the caller of this function has no way to understand
// we're bailing out because of 'division by zero'. Therefore, it will
// emit a 'expected relocatable expression' error. It would be nice to
// change this code to emit a better diagnostic.
if (RHS == 0)
return false;
if (ABE->getOpcode() == MCBinaryExpr::Div)
Result = LHS / RHS;
else
Result = LHS % RHS;
break;
case MCBinaryExpr::EQ: Result = LHS == RHS; break;
case MCBinaryExpr::GT: Result = LHS > RHS; break;
case MCBinaryExpr::GTE: Result = LHS >= RHS; break;
case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
case MCBinaryExpr::LOr: Result = LHS || RHS; break;
case MCBinaryExpr::LShr: Result = uint64_t(LHS) >> uint64_t(RHS); break;
case MCBinaryExpr::LT: Result = LHS < RHS; break;
case MCBinaryExpr::LTE: Result = LHS <= RHS; break;
case MCBinaryExpr::Mul: Result = LHS * RHS; break;
case MCBinaryExpr::NE: Result = LHS != RHS; break;
case MCBinaryExpr::Or: Result = LHS | RHS; break;
case MCBinaryExpr::OrNot: Result = LHS | ~RHS; break;
case MCBinaryExpr::Shl: Result = uint64_t(LHS) << uint64_t(RHS); break;
case MCBinaryExpr::Sub: Result = LHS - RHS; break;
case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
}
switch (Op) {
default:
Res = MCValue::get(Result);
break;
case MCBinaryExpr::EQ:
case MCBinaryExpr::GT:
case MCBinaryExpr::GTE:
case MCBinaryExpr::LT:
case MCBinaryExpr::LTE:
case MCBinaryExpr::NE:
// A comparison operator returns a -1 if true and 0 if false.
Res = MCValue::get(Result ? -1 : 0);
break;
}
return true;
}
case Specifier:
// Fold the expression during relocation generation. As parse time Asm might
// be null, and targets should not rely on the folding.
return Asm && Asm->getContext().getAsmInfo()->evaluateAsRelocatableImpl(
cast<MCSpecifierExpr>(*this), Res, Asm);
}
llvm_unreachable("Invalid assembly expression kind!");
}
MCFragment *MCExpr::findAssociatedFragment() const {
switch (getKind()) {
case Target:
// We never look through target specific expressions.
return cast<MCTargetExpr>(this)->findAssociatedFragment();
case Constant:
return MCSymbol::AbsolutePseudoFragment;
case SymbolRef: {
auto &Sym =
const_cast<MCSymbol &>(cast<MCSymbolRefExpr>(this)->getSymbol());
if (Sym.Fragment)
return Sym.Fragment;
if (Sym.isResolving())
return MCSymbol::AbsolutePseudoFragment;
Sym.setIsResolving(true);
auto *F = Sym.getFragment();
Sym.setIsResolving(false);
return F;
}
case Unary:
return cast<MCUnaryExpr>(this)->getSubExpr()->findAssociatedFragment();
case Binary: {
const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
MCFragment *LHS_F = BE->getLHS()->findAssociatedFragment();
MCFragment *RHS_F = BE->getRHS()->findAssociatedFragment();
// If either is absolute, return the other.
if (LHS_F == MCSymbol::AbsolutePseudoFragment)
return RHS_F;
if (RHS_F == MCSymbol::AbsolutePseudoFragment)
return LHS_F;
// Not always correct, but probably the best we can do without more context.
if (BE->getOpcode() == MCBinaryExpr::Sub)
return MCSymbol::AbsolutePseudoFragment;
// Otherwise, return the first non-null fragment.
return LHS_F ? LHS_F : RHS_F;
}
case Specifier:
return cast<MCSpecifierExpr>(this)->getSubExpr()->findAssociatedFragment();
}
llvm_unreachable("Invalid assembly expression kind!");
}
const MCSpecifierExpr *MCSpecifierExpr::create(const MCExpr *Expr, Spec S,
MCContext &Ctx, SMLoc Loc) {
return new (Ctx) MCSpecifierExpr(Expr, S, Loc);
}
const MCSpecifierExpr *MCSpecifierExpr::create(const MCSymbol *Sym, Spec S,
MCContext &Ctx, SMLoc Loc) {
return new (Ctx) MCSpecifierExpr(MCSymbolRefExpr::create(Sym, Ctx), S, Loc);
}
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