llvm/lib/MC/MCObjectWriter.cpp
Rafael Espindola 0eba49c22e Fix pr24486.
This extends the work done in r233995 so that now getFragment (in addition to
getSection) also works for variable symbols.

With that the existing logic to decide if a-b can be computed works even if
a or b are variables. Given that, the expression evaluation can avoid expanding
variables as aggressively and that in turn lets the relocation code see the
original variable.

In order for this to work with the asm streamer, there is now a dummy fragment
per section. It is used to assign a section to a symbol when no other fragment
exists.

This patch is a joint work by Maxim Ostapenko andy myself.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249303 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-05 12:07:05 +00:00

56 lines
1.8 KiB
C++

//===- lib/MC/MCObjectWriter.cpp - MCObjectWriter 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/MCAssembler.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSymbol.h"
using namespace llvm;
MCObjectWriter::~MCObjectWriter() {
}
bool MCObjectWriter::isSymbolRefDifferenceFullyResolved(
const MCAssembler &Asm, const MCSymbolRefExpr *A, const MCSymbolRefExpr *B,
bool InSet) const {
// Modified symbol references cannot be resolved.
if (A->getKind() != MCSymbolRefExpr::VK_None ||
B->getKind() != MCSymbolRefExpr::VK_None)
return false;
const MCSymbol &SA = A->getSymbol();
const MCSymbol &SB = B->getSymbol();
if (SA.isUndefined() || SB.isUndefined())
return false;
if (!SA.getFragment() || !SB.getFragment())
return false;
return isSymbolRefDifferenceFullyResolvedImpl(Asm, SA, SB, InSet);
}
bool MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
const MCAssembler &Asm, const MCSymbol &A, const MCSymbol &B,
bool InSet) const {
return isSymbolRefDifferenceFullyResolvedImpl(Asm, A, *B.getFragment(), InSet,
false);
}
bool MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
bool InSet, bool IsPCRel) const {
const MCSection &SecA = SymA.getSection();
const MCSection &SecB = *FB.getParent();
// On ELF and COFF A - B is absolute if A and B are in the same section.
return &SecA == &SecB;
}
bool MCObjectWriter::isWeak(const MCSymbol &) const { return false; }