llvm/lib/MC/MCExpr.cpp

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//===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;
void MCExpr::print(raw_ostream &OS) const {
switch (getKind()) {
case MCExpr::Target:
return cast<MCTargetExpr>(this)->PrintImpl(OS);
case MCExpr::Constant:
OS << cast<MCConstantExpr>(*this).getValue();
return;
case MCExpr::SymbolRef: {
const MCSymbol &Sym = cast<MCSymbolRefExpr>(*this).getSymbol();
// Parenthesize names that start with $ so that they don't look like
// absolute names.
if (Sym.getName()[0] == '$')
OS << '(' << Sym << ')';
else
OS << Sym;
return;
}
case MCExpr::Unary: {
const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
switch (UE.getOpcode()) {
default: assert(0 && "Invalid opcode!");
case MCUnaryExpr::LNot: OS << '!'; break;
case MCUnaryExpr::Minus: OS << '-'; break;
case MCUnaryExpr::Not: OS << '~'; break;
case MCUnaryExpr::Plus: OS << '+'; break;
}
OS << *UE.getSubExpr();
return;
}
case MCExpr::Binary: {
const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
// Only print parens around the LHS if it is non-trivial.
if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
OS << *BE.getLHS();
} else {
OS << '(' << *BE.getLHS() << ')';
}
switch (BE.getOpcode()) {
default: assert(0 && "Invalid opcode!");
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();
return;
}
}
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::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::Shl: OS << "<<"; break;
case MCBinaryExpr::Shr: OS << ">>"; break;
case MCBinaryExpr::Sub: OS << '-'; break;
case MCBinaryExpr::Xor: OS << '^'; break;
}
// Only print parens around the LHS if it is non-trivial.
if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
OS << *BE.getRHS();
} else {
OS << '(' << *BE.getRHS() << ')';
}
return;
}
}
assert(0 && "Invalid expression kind!");
}
void MCExpr::dump() const {
print(dbgs());
dbgs() << '\n';
}
/* *** */
const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
const MCExpr *RHS, MCContext &Ctx) {
return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
}
const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
MCContext &Ctx) {
return new (Ctx) MCUnaryExpr(Opc, Expr);
}
const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
return new (Ctx) MCConstantExpr(Value);
}
const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
MCContext &Ctx) {
return new (Ctx) MCSymbolRefExpr(Sym);
}
const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, MCContext &Ctx) {
return Create(Ctx.GetOrCreateSymbol(Name), Ctx);
}
const MCSymbolRefExpr *MCSymbolRefExpr::CreateTemp(StringRef Name,
MCContext &Ctx) {
return Create(Ctx.GetOrCreateTemporarySymbol(Name), Ctx);
}
void MCTargetExpr::Anchor() {}
/* *** */
bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAsmLayout *Layout) const {
MCValue Value;
if (!EvaluateAsRelocatable(Value, Layout) || !Value.isAbsolute())
return false;
Res = Value.getConstant();
return true;
}
static bool EvaluateSymbolicAdd(const MCValue &LHS, const MCSymbol *RHS_A,
const MCSymbol *RHS_B, int64_t RHS_Cst,
MCValue &Res) {
// We can't add or subtract two symbols.
if ((LHS.getSymA() && RHS_A) ||
(LHS.getSymB() && RHS_B))
return false;
const MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
const MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
if (B) {
// If we have a negated symbol, then we must have also have a non-negated
// symbol in order to encode the expression. We can do this check later to
// permit expressions which eventually fold to a representable form -- such
// as (a + (0 - b)) -- if necessary.
if (!A)
return false;
}
Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);
return true;
}
bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
const MCAsmLayout *Layout) const {
switch (getKind()) {
case Target:
return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout);
case Constant:
Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
return true;
case SymbolRef: {
const MCSymbol &Sym = cast<MCSymbolRefExpr>(this)->getSymbol();
// Evaluate recursively if this is a variable.
if (Sym.isVariable()) {
if (!Sym.getValue()->EvaluateAsRelocatable(Res, Layout))
return false;
// Absolutize symbol differences between defined symbols when we have a
// layout object and the target requests it.
if (Layout && Res.getSymB() &&
Layout->getAssembler().getBackend().hasAbsolutizedSet() &&
Res.getSymA()->isDefined() && Res.getSymB()->isDefined()) {
MCSymbolData &A = Layout->getAssembler().getSymbolData(*Res.getSymA());
MCSymbolData &B = Layout->getAssembler().getSymbolData(*Res.getSymB());
Res = MCValue::get(+ A.getFragment()->getAddress() + A.getOffset()
- B.getFragment()->getAddress() - B.getOffset()
+ Res.getConstant());
}
return true;
}
Res = MCValue::get(&Sym, 0, 0);
return true;
}
case Unary: {
const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
MCValue Value;
if (!AUE->getSubExpr()->EvaluateAsRelocatable(Value, Layout))
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.getSymA() && !Value.getSymB())
return false;
Res = MCValue::get(Value.getSymB(), Value.getSymA(),
-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()->EvaluateAsRelocatable(LHSValue, Layout) ||
!ABE->getRHS()->EvaluateAsRelocatable(RHSValue, Layout))
return false;
// We only support a few operations on non-constant expressions, handle
// those first.
if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
switch (ABE->getOpcode()) {
default:
return false;
case MCBinaryExpr::Sub:
// Negate RHS and add.
return EvaluateSymbolicAdd(LHSValue,
RHSValue.getSymB(), RHSValue.getSymA(),
-RHSValue.getConstant(),
Res);
case MCBinaryExpr::Add:
return EvaluateSymbolicAdd(LHSValue,
RHSValue.getSymA(), RHSValue.getSymB(),
RHSValue.getConstant(),
Res);
}
}
// FIXME: We need target hooks for the evaluation. It may be limited in
// width, and gas defines the result of comparisons and right shifts
// differently from Apple as.
int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
int64_t Result = 0;
switch (ABE->getOpcode()) {
case MCBinaryExpr::Add: Result = LHS + RHS; break;
case MCBinaryExpr::And: Result = LHS & RHS; break;
case MCBinaryExpr::Div: 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::LT: Result = LHS < RHS; break;
case MCBinaryExpr::LTE: Result = LHS <= RHS; break;
case MCBinaryExpr::Mod: 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::Shl: Result = LHS << RHS; break;
case MCBinaryExpr::Shr: Result = LHS >> RHS; break;
case MCBinaryExpr::Sub: Result = LHS - RHS; break;
case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
}
Res = MCValue::get(Result);
return true;
}
}
assert(0 && "Invalid assembly expression kind!");
return false;
}