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//===- MC-X86Specific.cpp - X86-Specific code for MC ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements X86-specific parsing, encoding and decoding stuff for
// MC.
//
//===----------------------------------------------------------------------===//
#include "AsmParser.h"
#include "llvm/MC/MCInst.h"
using namespace llvm;
/// X86Operand - Instances of this class represent one X86 machine instruction.
struct AsmParser::X86Operand {
enum {
Register,
Immediate,
Memory
} Kind;
union {
struct {
unsigned RegNo;
} Reg;
struct {
// FIXME: Should be a general expression.
int64_t Val;
} Imm;
struct {
unsigned SegReg;
int64_t Disp; // FIXME: Should be a general expression.
unsigned BaseReg;
unsigned Scale;
unsigned ScaleReg;
} Mem;
};
static X86Operand CreateReg(unsigned RegNo) {
X86Operand Res;
Res.Kind = Register;
Res.Reg.RegNo = RegNo;
return Res;
}
static X86Operand CreateImm(int64_t Val) {
X86Operand Res;
Res.Kind = Immediate;
Res.Imm.Val = Val;
return Res;
}
static X86Operand CreateMem(unsigned SegReg, int64_t Disp, unsigned BaseReg,
unsigned Scale, unsigned ScaleReg) {
X86Operand Res;
Res.Kind = Memory;
Res.Mem.SegReg = SegReg;
Res.Mem.Disp = Disp;
Res.Mem.BaseReg = BaseReg;
Res.Mem.Scale = Scale;
Res.Mem.ScaleReg = ScaleReg;
return Res;
}
void AddToMCInst(MCInst &I) {
// FIXME: Add in x86 order here.
}
};
bool AsmParser::ParseX86Operand(X86Operand &Op) {
switch (Lexer.getKind()) {
default:
return ParseX86MemOperand(Op);
case asmtok::Register:
// FIXME: Decode reg #.
// FIXME: if a segment register, this could either be just the seg reg, or
// the start of a memory operand.
Op = X86Operand::CreateReg(123);
Lexer.Lex(); // Eat register.
return false;
case asmtok::Dollar: {
// $42 -> immediate.
Lexer.Lex();
int64_t Val;
if (ParseExpression(Val))
return TokError("expected integer constant");
Op = X86Operand::CreateReg(Val);
return false;
case asmtok::Star:
Lexer.Lex(); // Eat the star.
if (Lexer.is(asmtok::Register)) {
Op = X86Operand::CreateReg(123);
Lexer.Lex(); // Eat register.
} else if (ParseX86MemOperand(Op))
return true;
// FIXME: Note that these are 'dereferenced' so that clients know the '*' is
// there.
return false;
}
}
}
/// ParseX86MemOperand: segment: disp(basereg, indexreg, scale)
bool AsmParser::ParseX86MemOperand(X86Operand &Op) {
// FIXME: If SegReg ':' (e.g. %gs:), eat and remember.
unsigned SegReg = 0;
// We have to disambiguate a parenthesized expression "(4+5)" from the start
// of a memory operand with a missing displacement "(%ebx)" or "(,%eax)". The
// only way to do this without lookahead is to eat the ( and see what is after
// it.
int64_t Disp = 0;
if (Lexer.isNot(asmtok::LParen)) {
if (ParseExpression(Disp)) return true;
// After parsing the base expression we could either have a parenthesized
// memory address or not. If not, return now. If so, eat the (.
if (Lexer.isNot(asmtok::LParen)) {
Op = X86Operand::CreateMem(SegReg, Disp, 0, 0, 0);
return false;
}
// Eat the '('.
Lexer.Lex();
} else {
// Okay, we have a '('. We don't know if this is an expression or not, but
// so we have to eat the ( to see beyond it.
Lexer.Lex(); // Eat the '('.
if (Lexer.is(asmtok::Register) || Lexer.is(asmtok::Comma)) {
// Nothing to do here, fall into the code below with the '(' part of the
// memory operand consumed.
} else {
// It must be an parenthesized expression, parse it now.
if (ParseParenExpr(Disp) ||
ParseBinOpRHS(1, Disp))
return true;
// After parsing the base expression we could either have a parenthesized
// memory address or not. If not, return now. If so, eat the (.
if (Lexer.isNot(asmtok::LParen)) {
Op = X86Operand::CreateMem(SegReg, Disp, 0, 0, 0);
return false;
}
// Eat the '('.
Lexer.Lex();
}
}
// If we reached here, then we just ate the ( of the memory operand. Process
// the rest of the memory operand.
unsigned BaseReg = 0, ScaleReg = 0, Scale = 0;
if (Lexer.is(asmtok::Register)) {
BaseReg = 123; // FIXME: decode reg #
Lexer.Lex(); // eat the register.
}
if (Lexer.is(asmtok::Comma)) {
Lexer.Lex(); // eat the comma.
if (Lexer.is(asmtok::Register)) {
ScaleReg = 123; // FIXME: decode reg #
Lexer.Lex(); // eat the register.
Scale = 1; // If not specified, the scale defaults to 1.
}
if (Lexer.is(asmtok::Comma)) {
Lexer.Lex(); // eat the comma.
// If present, get and validate scale amount.
if (Lexer.is(asmtok::IntVal)) {
int64_t ScaleVal = Lexer.getCurIntVal();
if (ScaleVal != 1 && ScaleVal != 2 && ScaleVal != 4 && ScaleVal != 8)
return TokError("scale factor in address must be 1, 2, 4 or 8");
Lexer.Lex(); // eat the scale.
Scale = (unsigned)ScaleVal;
}
}
}
// Ok, we've eaten the memory operand, verify we have a ')' and eat it too.
if (Lexer.isNot(asmtok::RParen))
return TokError("unexpected token in memory operand");
Lexer.Lex(); // Eat the ')'.
Op = X86Operand::CreateMem(SegReg, Disp, BaseReg, Scale, ScaleReg);
return false;
}
/// ParseX86InstOperands - Parse the operands of an X86 instruction and return
/// them as the operands of an MCInst.
bool AsmParser::ParseX86InstOperands(MCInst &Inst) {
// If no operands are present, just return.
if (Lexer.is(asmtok::EndOfStatement))
return false;
// Read the first operand.
X86Operand Op;
if (ParseX86Operand(Op))
return true;
Op.AddToMCInst(Inst);
while (Lexer.is(asmtok::Comma)) {
Lexer.Lex(); // Eat the comma.
// Parse and remember the operand.
Op = X86Operand();
if (ParseX86Operand(Op))
return true;
Op.AddToMCInst(Inst);
}
return false;
}
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