llvm-6502/lib/MC/MCObjectStreamer.cpp
Rafael Espindola 5d4918dbd1 There are two reasons why we might want to use
foo = a - b
.long foo
instead of just
.long a - b

First, on darwin9 64 bits the assembler produces the wrong result. Second,
if "a" is the end of the section all darwin assemblers (9, 10 and mc) will not
consider a - b to be a constant but will if the dummy foo is created.

Split how we handle these cases. The first one is something MC should take care
of. The second one has to be handled by the caller.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120889 91177308-0d34-0410-b5e6-96231b3b80d8
2010-12-04 03:21:47 +00:00

222 lines
7.5 KiB
C++

//===- lib/MC/MCObjectStreamer.cpp - Object File MCStreamer Interface -----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;
MCObjectStreamer::MCObjectStreamer(MCContext &Context, TargetAsmBackend &TAB,
raw_ostream &_OS, MCCodeEmitter *_Emitter,
bool _PadSectionToAlignment)
: MCStreamer(Context), Assembler(new MCAssembler(Context, TAB,
*_Emitter,
_PadSectionToAlignment,
_OS)),
CurSectionData(0)
{
}
MCObjectStreamer::~MCObjectStreamer() {
delete &Assembler->getBackend();
delete &Assembler->getEmitter();
delete Assembler;
}
MCFragment *MCObjectStreamer::getCurrentFragment() const {
assert(getCurrentSectionData() && "No current section!");
if (!getCurrentSectionData()->empty())
return &getCurrentSectionData()->getFragmentList().back();
return 0;
}
MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() const {
MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
if (!F)
F = new MCDataFragment(getCurrentSectionData());
return F;
}
const MCExpr *MCObjectStreamer::AddValueSymbols(const MCExpr *Value) {
switch (Value->getKind()) {
case MCExpr::Target: llvm_unreachable("Can't handle target exprs yet!");
case MCExpr::Constant:
break;
case MCExpr::Binary: {
const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
AddValueSymbols(BE->getLHS());
AddValueSymbols(BE->getRHS());
break;
}
case MCExpr::SymbolRef:
Assembler->getOrCreateSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
break;
case MCExpr::Unary:
AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
break;
}
return Value;
}
void MCObjectStreamer::EmitValue(const MCExpr *Value, unsigned Size,
unsigned AddrSpace) {
assert(AddrSpace == 0 && "Address space must be 0!");
MCDataFragment *DF = getOrCreateDataFragment();
// Avoid fixups when possible.
int64_t AbsValue;
if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue, &getAssembler())) {
EmitIntValue(AbsValue, Size, AddrSpace);
return;
}
DF->addFixup(MCFixup::Create(DF->getContents().size(),
AddValueSymbols(Value),
MCFixup::getKindForSize(Size, false)));
DF->getContents().resize(DF->getContents().size() + Size, 0);
}
void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
assert(CurSection && "Cannot emit before setting section!");
Symbol->setSection(*CurSection);
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
// FIXME: This is wasteful, we don't necessarily need to create a data
// fragment. Instead, we should mark the symbol as pointing into the data
// fragment if it exists, otherwise we should just queue the label and set its
// fragment pointer when we emit the next fragment.
MCDataFragment *F = getOrCreateDataFragment();
assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
SD.setFragment(F);
SD.setOffset(F->getContents().size());
}
void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value,
unsigned AddrSpace) {
int64_t IntValue;
if (Value->EvaluateAsAbsolute(IntValue, &getAssembler())) {
EmitULEB128IntValue(IntValue, AddrSpace);
return;
}
new MCLEBFragment(*Value, false, getCurrentSectionData());
}
void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value,
unsigned AddrSpace) {
int64_t IntValue;
if (Value->EvaluateAsAbsolute(IntValue, &getAssembler())) {
EmitSLEB128IntValue(IntValue, AddrSpace);
return;
}
new MCLEBFragment(*Value, true, getCurrentSectionData());
}
void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
const MCSymbol *Symbol) {
report_fatal_error("This file format doesn't support weak aliases.");
}
void MCObjectStreamer::SwitchSection(const MCSection *Section) {
assert(Section && "Cannot switch to a null section!");
// If already in this section, then this is a noop.
if (Section == CurSection) return;
PrevSection = CurSection;
CurSection = Section;
CurSectionData = &getAssembler().getOrCreateSectionData(*Section);
}
void MCObjectStreamer::EmitInstruction(const MCInst &Inst) {
// Scan for values.
for (unsigned i = Inst.getNumOperands(); i--; )
if (Inst.getOperand(i).isExpr())
AddValueSymbols(Inst.getOperand(i).getExpr());
getCurrentSectionData()->setHasInstructions(true);
// Now that a machine instruction has been assembled into this section, make
// a line entry for any .loc directive that has been seen.
MCLineEntry::Make(this, getCurrentSection());
// If this instruction doesn't need relaxation, just emit it as data.
if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
EmitInstToData(Inst);
return;
}
// Otherwise, if we are relaxing everything, relax the instruction as much as
// possible and emit it as data.
if (getAssembler().getRelaxAll()) {
MCInst Relaxed;
getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
EmitInstToData(Relaxed);
return;
}
// Otherwise emit to a separate fragment.
EmitInstToFragment(Inst);
}
void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst) {
MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
raw_svector_ostream VecOS(IF->getCode());
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups());
}
void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
const MCSymbol *LastLabel,
const MCSymbol *Label) {
if (!LastLabel) {
int PointerSize = getAssembler().getBackend().getPointerSize();
EmitDwarfSetLineAddr(LineDelta, Label, PointerSize);
return;
}
MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
const MCExpr *LabelRef =
MCSymbolRefExpr::Create(Label, Variant, getContext());
const MCExpr *LastLabelRef =
MCSymbolRefExpr::Create(LastLabel, Variant, getContext());
const MCExpr *AddrDelta =
MCBinaryExpr::Create(MCBinaryExpr::Sub, LabelRef, LastLabelRef,
getContext());
int64_t Res;
if (AddrDelta->EvaluateAsAbsolute(Res, &getAssembler())) {
MCDwarfLineAddr::Emit(this, LineDelta, Res);
return;
}
new MCDwarfLineAddrFragment(LineDelta, *AddrDelta, getCurrentSectionData());
}
void MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
unsigned char Value) {
new MCOrgFragment(*Offset, Value, getCurrentSectionData());
}
void MCObjectStreamer::Finish() {
getAssembler().Finish();
}