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036c130e90
Document that MCExpr::Div, Mod, and the comparison operators are all signed operators. Document that the comparison operators' results are target-dependent. Document that the behavior of shr is target-dependent. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95619 91177308-0d34-0410-b5e6-96231b3b80d8
288 lines
8.9 KiB
C++
288 lines
8.9 KiB
C++
//===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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void MCExpr::print(raw_ostream &OS) const {
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switch (getKind()) {
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case MCExpr::Target:
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return cast<MCTargetExpr>(this)->PrintImpl(OS);
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case MCExpr::Constant:
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OS << cast<MCConstantExpr>(*this).getValue();
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return;
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case MCExpr::SymbolRef: {
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const MCSymbol &Sym = cast<MCSymbolRefExpr>(*this).getSymbol();
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// Parenthesize names that start with $ so that they don't look like
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// absolute names.
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if (Sym.getName()[0] == '$')
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OS << '(' << Sym << ')';
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else
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OS << Sym;
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return;
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}
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case MCExpr::Unary: {
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const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
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switch (UE.getOpcode()) {
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default: assert(0 && "Invalid opcode!");
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case MCUnaryExpr::LNot: OS << '!'; break;
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case MCUnaryExpr::Minus: OS << '-'; break;
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case MCUnaryExpr::Not: OS << '~'; break;
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case MCUnaryExpr::Plus: OS << '+'; break;
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}
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OS << *UE.getSubExpr();
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return;
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}
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case MCExpr::Binary: {
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const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
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// Only print parens around the LHS if it is non-trivial.
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if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
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OS << *BE.getLHS();
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} else {
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OS << '(' << *BE.getLHS() << ')';
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}
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switch (BE.getOpcode()) {
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default: assert(0 && "Invalid opcode!");
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case MCBinaryExpr::Add:
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// Print "X-42" instead of "X+-42".
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if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
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if (RHSC->getValue() < 0) {
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OS << RHSC->getValue();
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return;
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}
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}
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OS << '+';
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break;
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case MCBinaryExpr::And: OS << '&'; break;
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case MCBinaryExpr::Div: OS << '/'; break;
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case MCBinaryExpr::EQ: OS << "=="; break;
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case MCBinaryExpr::GT: OS << '>'; break;
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case MCBinaryExpr::GTE: OS << ">="; break;
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case MCBinaryExpr::LAnd: OS << "&&"; break;
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case MCBinaryExpr::LOr: OS << "||"; break;
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case MCBinaryExpr::LT: OS << '<'; break;
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case MCBinaryExpr::LTE: OS << "<="; break;
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case MCBinaryExpr::Mod: OS << '%'; break;
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case MCBinaryExpr::Mul: OS << '*'; break;
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case MCBinaryExpr::NE: OS << "!="; break;
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case MCBinaryExpr::Or: OS << '|'; break;
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case MCBinaryExpr::Shl: OS << "<<"; break;
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case MCBinaryExpr::Shr: OS << ">>"; break;
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case MCBinaryExpr::Sub: OS << '-'; break;
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case MCBinaryExpr::Xor: OS << '^'; break;
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}
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// Only print parens around the LHS if it is non-trivial.
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if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
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OS << *BE.getRHS();
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} else {
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OS << '(' << *BE.getRHS() << ')';
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}
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return;
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}
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}
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assert(0 && "Invalid expression kind!");
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}
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void MCExpr::dump() const {
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print(dbgs());
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dbgs() << '\n';
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}
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/* *** */
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const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
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const MCExpr *RHS, MCContext &Ctx) {
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return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
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}
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const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
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MCContext &Ctx) {
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return new (Ctx) MCUnaryExpr(Opc, Expr);
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}
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const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
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return new (Ctx) MCConstantExpr(Value);
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}
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const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
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MCContext &Ctx) {
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return new (Ctx) MCSymbolRefExpr(Sym);
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}
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const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, MCContext &Ctx) {
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return Create(Ctx.GetOrCreateSymbol(Name), Ctx);
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}
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void MCTargetExpr::Anchor() {}
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/* *** */
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bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const {
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MCValue Value;
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if (!EvaluateAsRelocatable(Value) || !Value.isAbsolute())
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return false;
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Res = Value.getConstant();
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return true;
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}
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static bool EvaluateSymbolicAdd(const MCValue &LHS, const MCSymbol *RHS_A,
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const MCSymbol *RHS_B, int64_t RHS_Cst,
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MCValue &Res) {
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// We can't add or subtract two symbols.
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if ((LHS.getSymA() && RHS_A) ||
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(LHS.getSymB() && RHS_B))
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return false;
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const MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
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const MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
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if (B) {
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// If we have a negated symbol, then we must have also have a non-negated
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// symbol in order to encode the expression. We can do this check later to
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// permit expressions which eventually fold to a representable form -- such
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// as (a + (0 - b)) -- if necessary.
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if (!A)
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return false;
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}
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Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);
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return true;
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}
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bool MCExpr::EvaluateAsRelocatable(MCValue &Res) const {
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switch (getKind()) {
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case Target:
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return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res);
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case Constant:
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Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
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return true;
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case SymbolRef: {
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const MCSymbol &Sym = cast<MCSymbolRefExpr>(this)->getSymbol();
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// Evaluate recursively if this is a variable.
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if (Sym.isVariable())
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return Sym.getValue()->EvaluateAsRelocatable(Res);
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Res = MCValue::get(&Sym, 0, 0);
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return true;
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}
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case Unary: {
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const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
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MCValue Value;
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if (!AUE->getSubExpr()->EvaluateAsRelocatable(Value))
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return false;
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switch (AUE->getOpcode()) {
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case MCUnaryExpr::LNot:
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if (!Value.isAbsolute())
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return false;
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Res = MCValue::get(!Value.getConstant());
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break;
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case MCUnaryExpr::Minus:
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/// -(a - b + const) ==> (b - a - const)
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if (Value.getSymA() && !Value.getSymB())
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return false;
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Res = MCValue::get(Value.getSymB(), Value.getSymA(),
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-Value.getConstant());
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break;
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case MCUnaryExpr::Not:
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if (!Value.isAbsolute())
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return false;
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Res = MCValue::get(~Value.getConstant());
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break;
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case MCUnaryExpr::Plus:
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Res = Value;
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break;
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}
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return true;
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}
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case Binary: {
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const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
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MCValue LHSValue, RHSValue;
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if (!ABE->getLHS()->EvaluateAsRelocatable(LHSValue) ||
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!ABE->getRHS()->EvaluateAsRelocatable(RHSValue))
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return false;
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// We only support a few operations on non-constant expressions, handle
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// those first.
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if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
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switch (ABE->getOpcode()) {
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default:
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return false;
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case MCBinaryExpr::Sub:
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// Negate RHS and add.
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return EvaluateSymbolicAdd(LHSValue,
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RHSValue.getSymB(), RHSValue.getSymA(),
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-RHSValue.getConstant(),
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Res);
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case MCBinaryExpr::Add:
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return EvaluateSymbolicAdd(LHSValue,
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RHSValue.getSymA(), RHSValue.getSymB(),
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RHSValue.getConstant(),
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Res);
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}
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}
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// FIXME: We need target hooks for the evaluation. It may be limited in
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// width, and gas defines the result of comparisons and right shifts
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// differently from Apple as.
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int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
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int64_t Result = 0;
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switch (ABE->getOpcode()) {
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case MCBinaryExpr::Add: Result = LHS + RHS; break;
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case MCBinaryExpr::And: Result = LHS & RHS; break;
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case MCBinaryExpr::Div: Result = LHS / RHS; break;
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case MCBinaryExpr::EQ: Result = LHS == RHS; break;
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case MCBinaryExpr::GT: Result = LHS > RHS; break;
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case MCBinaryExpr::GTE: Result = LHS >= RHS; break;
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case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
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case MCBinaryExpr::LOr: Result = LHS || RHS; break;
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case MCBinaryExpr::LT: Result = LHS < RHS; break;
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case MCBinaryExpr::LTE: Result = LHS <= RHS; break;
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case MCBinaryExpr::Mod: Result = LHS % RHS; break;
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case MCBinaryExpr::Mul: Result = LHS * RHS; break;
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case MCBinaryExpr::NE: Result = LHS != RHS; break;
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case MCBinaryExpr::Or: Result = LHS | RHS; break;
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case MCBinaryExpr::Shl: Result = LHS << RHS; break;
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case MCBinaryExpr::Shr: Result = LHS >> RHS; break;
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case MCBinaryExpr::Sub: Result = LHS - RHS; break;
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case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
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}
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Res = MCValue::get(Result);
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return true;
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}
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}
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assert(0 && "Invalid assembly expression kind!");
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return false;
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}
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