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llvm-mirror/lib/MC/MCSectionCOFF.cpp
Rafael Espindola 34f7950ebf Fix a few issues with comdat handling on COFF.
* Section association cannot use just the section name as many
sections can have the same name. With this patch, the comdat symbol in
an assoc section is interpreted to mean a symbol in the associated
section and the mapping is discovered from it.

* Comdat symbols were not being set correctly. Instead we were getting
whatever was output first for that section.

A consequence is that associative sections now must use .section to
set the association. Using .linkonce would not work since it is not
possible to change a sections comdat symbol (it is used to decide if
we should create a new section or reuse an existing one).

This includes r210298, which was reverted because it was asserting
on an associated section having the same comdat as the associated
section.

llvm-svn: 210367
2014-06-06 19:26:12 +00:00

105 lines
3.0 KiB
C++

//===- lib/MC/MCSectionCOFF.cpp - COFF Code Section Representation --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
MCSectionCOFF::~MCSectionCOFF() {} // anchor.
// ShouldOmitSectionDirective - Decides whether a '.section' directive
// should be printed before the section name
bool MCSectionCOFF::ShouldOmitSectionDirective(StringRef Name,
const MCAsmInfo &MAI) const {
if (COMDATSymbol)
return false;
// FIXME: Does .section .bss/.data/.text work everywhere??
if (Name == ".text" || Name == ".data" || Name == ".bss")
return true;
return false;
}
void MCSectionCOFF::setSelection(int Selection) const {
assert(Selection != 0 && "invalid COMDAT selection type");
this->Selection = Selection;
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
}
void MCSectionCOFF::PrintSwitchToSection(const MCAsmInfo &MAI,
raw_ostream &OS,
const MCExpr *Subsection) const {
// standard sections don't require the '.section'
if (ShouldOmitSectionDirective(SectionName, MAI)) {
OS << '\t' << getSectionName() << '\n';
return;
}
OS << "\t.section\t" << getSectionName() << ",\"";
if (getKind().isText())
OS << 'x';
else if (getKind().isBSS())
OS << 'b';
if (getKind().isWriteable())
OS << 'w';
else
OS << 'r';
if (getCharacteristics() & COFF::IMAGE_SCN_MEM_DISCARDABLE)
OS << 'n';
if (getCharacteristics() & COFF::IMAGE_SCN_CNT_INITIALIZED_DATA)
OS << 'd';
OS << '"';
if (getCharacteristics() & COFF::IMAGE_SCN_LNK_COMDAT) {
OS << ",";
switch (Selection) {
case COFF::IMAGE_COMDAT_SELECT_NODUPLICATES:
OS << "one_only,";
break;
case COFF::IMAGE_COMDAT_SELECT_ANY:
OS << "discard,";
break;
case COFF::IMAGE_COMDAT_SELECT_SAME_SIZE:
OS << "same_size,";
break;
case COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH:
OS << "same_contents,";
break;
case COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE:
OS << "associative,";
break;
case COFF::IMAGE_COMDAT_SELECT_LARGEST:
OS << "largest,";
break;
case COFF::IMAGE_COMDAT_SELECT_NEWEST:
OS << "newest,";
break;
default:
assert (0 && "unsupported COFF selection type");
break;
}
assert(COMDATSymbol);
OS << *COMDATSymbol;
}
OS << '\n';
}
bool MCSectionCOFF::UseCodeAlign() const {
return getKind().isText();
}
bool MCSectionCOFF::isVirtualSection() const {
return getCharacteristics() & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;
}