diff options
Diffstat (limited to 'lib/MC/MCExpr.cpp')
-rw-r--r-- | lib/MC/MCExpr.cpp | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/lib/MC/MCExpr.cpp b/lib/MC/MCExpr.cpp new file mode 100644 index 0000000..0f3e053 --- /dev/null +++ b/lib/MC/MCExpr.cpp @@ -0,0 +1,286 @@ +//===- 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/MCContext.h" +#include "llvm/MC/MCSymbol.h" +#include "llvm/MC/MCValue.h" +#include "llvm/Support/raw_ostream.h" +using namespace llvm; + +void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI) const { + switch (getKind()) { + 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.print(OS, MAI); + OS << ')'; + } else { + Sym.print(OS, MAI); + } + 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; + } + UE.getSubExpr()->print(OS, MAI); + 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())) { + BE.getLHS()->print(OS, MAI); + } else { + OS << '('; + BE.getLHS()->print(OS, MAI); + OS << ')'; + } + + 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())) { + BE.getRHS()->print(OS, MAI); + } else { + OS << '('; + BE.getRHS()->print(OS, MAI); + OS << ')'; + } + return; + } + } + + assert(0 && "Invalid expression kind!"); +} + +void MCExpr::dump() const { + print(errs(), 0); + errs() << '\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(const StringRef &Name, + MCContext &Ctx) { + return Create(Ctx.GetOrCreateSymbol(Name), Ctx); +} + + +/* *** */ + +bool MCExpr::EvaluateAsAbsolute(MCContext &Ctx, int64_t &Res) const { + MCValue Value; + + if (!EvaluateAsRelocatable(Ctx, Value) || !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(MCContext &Ctx, MCValue &Res) const { + switch (getKind()) { + case Constant: + Res = MCValue::get(cast<MCConstantExpr>(this)->getValue()); + return true; + + case SymbolRef: { + const MCSymbol &Sym = cast<MCSymbolRefExpr>(this)->getSymbol(); + if (const MCValue *Value = Ctx.GetSymbolValue(&Sym)) + Res = *Value; + else + Res = MCValue::get(&Sym, 0, 0); + return true; + } + + case Unary: { + const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this); + MCValue Value; + + if (!AUE->getSubExpr()->EvaluateAsRelocatable(Ctx, Value)) + 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(Ctx, LHSValue) || + !ABE->getRHS()->EvaluateAsRelocatable(Ctx, RHSValue)) + 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 differently from Apple + // as (the result is sign extended). + 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; +} |