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//===- AsmExpr.cpp - Assembly file expressions ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "AsmExpr.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
using namespace llvm;
AsmExpr::~AsmExpr() {
}
bool AsmExpr::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, MCSymbol *RHS_A,
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;
MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
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 AsmExpr::EvaluateAsRelocatable(MCContext &Ctx, MCValue &Res) const {
switch (getKind()) {
default:
assert(0 && "Invalid assembly expression kind!");
case Constant:
Res = MCValue::get(cast<AsmConstantExpr>(this)->getValue());
return true;
case SymbolRef: {
MCSymbol *Sym = cast<AsmSymbolRefExpr>(this)->getSymbol();
if (const MCValue *Value = Ctx.GetSymbolValue(Sym))
Res = *Value;
else
Res = MCValue::get(Sym, 0, 0);
return true;
}
case Unary: {
const AsmUnaryExpr *AUE = cast<AsmUnaryExpr>(this);
MCValue Value;
if (!AUE->getSubExpr()->EvaluateAsRelocatable(Ctx, Value))
return false;
switch (AUE->getOpcode()) {
case AsmUnaryExpr::LNot:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(!Value.getConstant());
break;
case AsmUnaryExpr::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 AsmUnaryExpr::Not:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(~Value.getConstant());
break;
case AsmUnaryExpr::Plus:
Res = Value;
break;
}
return true;
}
case Binary: {
const AsmBinaryExpr *ABE = cast<AsmBinaryExpr>(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 AsmBinaryExpr::Sub:
// Negate RHS and add.
return EvaluateSymbolicAdd(LHSValue,
RHSValue.getSymB(), RHSValue.getSymA(),
-RHSValue.getConstant(),
Res);
case AsmBinaryExpr::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 AsmBinaryExpr::Add: Result = LHS + RHS; break;
case AsmBinaryExpr::And: Result = LHS & RHS; break;
case AsmBinaryExpr::Div: Result = LHS / RHS; break;
case AsmBinaryExpr::EQ: Result = LHS == RHS; break;
case AsmBinaryExpr::GT: Result = LHS > RHS; break;
case AsmBinaryExpr::GTE: Result = LHS >= RHS; break;
case AsmBinaryExpr::LAnd: Result = LHS && RHS; break;
case AsmBinaryExpr::LOr: Result = LHS || RHS; break;
case AsmBinaryExpr::LT: Result = LHS < RHS; break;
case AsmBinaryExpr::LTE: Result = LHS <= RHS; break;
case AsmBinaryExpr::Mod: Result = LHS % RHS; break;
case AsmBinaryExpr::Mul: Result = LHS * RHS; break;
case AsmBinaryExpr::NE: Result = LHS != RHS; break;
case AsmBinaryExpr::Or: Result = LHS | RHS; break;
case AsmBinaryExpr::Shl: Result = LHS << RHS; break;
case AsmBinaryExpr::Shr: Result = LHS >> RHS; break;
case AsmBinaryExpr::Sub: Result = LHS - RHS; break;
case AsmBinaryExpr::Xor: Result = LHS ^ RHS; break;
}
Res = MCValue::get(Result);
return true;
}
}
}
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