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087aad44cb37b361e8ed84f197138b366c764f9a
llvm-6502/lib/CodeGen/AsmPrinter/DwarfTableException.cpp
Bill Wendling 087aad44cb Remove a flag that would set the ".eh" symbol as .globl. MachO was the only one 
who used this flag, and it now emits CFI and doesn't emit this anymore. All
other targets left this flag "false".
<rdar://problem/8486371>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130918 91177308-0d34-0410-b5e6-96231b3b80d8
2011-05-05 06:49:15 +00:00

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//===-- CodeGen/AsmPrinter/DwarfTableException.cpp - Dwarf Exception Impl --==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing DWARF exception info into asm files.
// The implementation emits all the necessary tables "by hands".
//
//===----------------------------------------------------------------------===//
#include "DwarfException.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
using namespace llvm;
DwarfTableException::DwarfTableException(AsmPrinter *A)
: DwarfException(A),
shouldEmitTable(false), shouldEmitMoves(false),
shouldEmitTableModule(false), shouldEmitMovesModule(false) {}
DwarfTableException::~DwarfTableException() {}
/// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
/// is shared among many Frame Description Entries. There is at least one CIE
/// in every non-empty .debug_frame section.
void DwarfTableException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
// Size and sign of stack growth.
int stackGrowth = Asm->getTargetData().getPointerSize();
if (Asm->TM.getFrameLowering()->getStackGrowthDirection() ==
TargetFrameLowering::StackGrowsDown)
stackGrowth *= -1;
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
// Begin eh frame section.
Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
MCSymbol *EHFrameSym;
if (TLOF.isFunctionEHFrameSymbolPrivate())
EHFrameSym = Asm->GetTempSymbol("EH_frame", Index);
else
EHFrameSym = Asm->OutContext.GetOrCreateSymbol(Twine("EH_frame") +
Twine(Index));
Asm->OutStreamer.EmitLabel(EHFrameSym);
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("section_eh_frame", Index));
// Define base labels.
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common", Index));
// Define the eh frame length.
Asm->OutStreamer.AddComment("Length of Common Information Entry");
Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_frame_common_end", Index),
Asm->GetTempSymbol("eh_frame_common_begin", Index),
4);
// EH frame header.
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_begin",Index));
Asm->OutStreamer.AddComment("CIE Identifier Tag");
Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
Asm->OutStreamer.AddComment("DW_CIE_VERSION");
Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
// The personality presence indicates that language specific information will
// show up in the eh frame. Find out how we are supposed to lower the
// personality function reference:
unsigned LSDAEncoding = TLOF.getLSDAEncoding();
unsigned FDEEncoding = TLOF.getFDEEncoding(false);
unsigned PerEncoding = TLOF.getPersonalityEncoding();
char Augmentation[6] = { 0 };
unsigned AugmentationSize = 0;
char *APtr = Augmentation + 1;
if (PersonalityFn) {
// There is a personality function.
*APtr++ = 'P';
AugmentationSize += 1 + Asm->GetSizeOfEncodedValue(PerEncoding);
}
if (UsesLSDA[Index]) {
// An LSDA pointer is in the FDE augmentation.
*APtr++ = 'L';
++AugmentationSize;
}
if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
// A non-default pointer encoding for the FDE.
*APtr++ = 'R';
++AugmentationSize;
}
if (APtr != Augmentation + 1)
Augmentation[0] = 'z';
Asm->OutStreamer.AddComment("CIE Augmentation");
Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);
// Round out reader.
Asm->EmitULEB128(1, "CIE Code Alignment Factor");
Asm->EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
Asm->OutStreamer.AddComment("CIE Return Address Column");
const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo();
const TargetFrameLowering *TFI = Asm->TM.getFrameLowering();
Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
if (Augmentation[0]) {
Asm->EmitULEB128(AugmentationSize, "Augmentation Size");
// If there is a personality, we need to indicate the function's location.
if (PersonalityFn) {
Asm->EmitEncodingByte(PerEncoding, "Personality");
Asm->OutStreamer.AddComment("Personality");
Asm->EmitReference(PersonalityFn, PerEncoding);
}
if (UsesLSDA[Index])
Asm->EmitEncodingByte(LSDAEncoding, "LSDA");
if (FDEEncoding != dwarf::DW_EH_PE_absptr)
Asm->EmitEncodingByte(FDEEncoding, "FDE");
}
// Indicate locations of general callee saved registers in frame.
std::vector<MachineMove> Moves;
TFI->getInitialFrameState(Moves);
Asm->EmitFrameMoves(Moves, 0, true);
// On Darwin the linker honors the alignment of eh_frame, which means it must
// be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
// holes which confuse readers of eh_frame.
Asm->EmitAlignment(Asm->getTargetData().getPointerSize() == 4 ? 2 : 3);
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_end", Index));
}
/// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
void DwarfTableException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
"Should not emit 'available externally' functions at all");
const Function *TheFunc = EHFrameInfo.function;
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned LSDAEncoding = TLOF.getLSDAEncoding();
unsigned FDEEncoding = TLOF.getFDEEncoding(false);
Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
// If corresponding function is weak definition, this should be too.
if (TheFunc->isWeakForLinker() && Asm->MAI->getWeakDefDirective())
Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
MCSA_WeakDefinition);
// If corresponding function is hidden, this should be too.
if (TheFunc->hasHiddenVisibility())
if (MCSymbolAttr HiddenAttr = Asm->MAI->getHiddenVisibilityAttr())
Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
HiddenAttr);
// If there are no calls then you can't unwind. This may mean we can omit the
// EH Frame, but some environments do not handle weak absolute symbols. If
// UnwindTablesMandatory is set we cannot do this optimization; the unwind
// info is to be available for non-EH uses.
if (!EHFrameInfo.adjustsStack && !UnwindTablesMandatory &&
(!TheFunc->isWeakForLinker() ||
!Asm->MAI->getWeakDefDirective() ||
TLOF.getSupportsWeakOmittedEHFrame())) {
Asm->OutStreamer.EmitAssignment(EHFrameInfo.FunctionEHSym,
MCConstantExpr::Create(0, Asm->OutContext));
// This name has no connection to the function, so it might get
// dead-stripped when the function is not, erroneously. Prohibit
// dead-stripping unconditionally.
if (Asm->MAI->hasNoDeadStrip())
Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
MCSA_NoDeadStrip);
} else {
Asm->OutStreamer.EmitLabel(EHFrameInfo.FunctionEHSym);
// EH frame header.
Asm->OutStreamer.AddComment("Length of Frame Information Entry");
Asm->EmitLabelDifference(
Asm->GetTempSymbol("eh_frame_end", EHFrameInfo.Number),
Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number), 4);
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_begin",
EHFrameInfo.Number));
Asm->OutStreamer.AddComment("FDE CIE offset");
Asm->EmitLabelDifference(
Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number),
Asm->GetTempSymbol("eh_frame_common",
EHFrameInfo.PersonalityIndex), 4);
MCSymbol *EHFuncBeginSym =
Asm->GetTempSymbol("eh_func_begin", EHFrameInfo.Number);
Asm->OutStreamer.AddComment("FDE initial location");
Asm->EmitReference(EHFuncBeginSym, FDEEncoding);
Asm->OutStreamer.AddComment("FDE address range");
Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_func_end",
EHFrameInfo.Number),
EHFuncBeginSym,
Asm->GetSizeOfEncodedValue(FDEEncoding));
// If there is a personality and landing pads then point to the language
// specific data area in the exception table.
if (MMI->getPersonalities()[0] != NULL) {
unsigned Size = Asm->GetSizeOfEncodedValue(LSDAEncoding);
Asm->EmitULEB128(Size, "Augmentation size");
Asm->OutStreamer.AddComment("Language Specific Data Area");
if (EHFrameInfo.hasLandingPads)
Asm->EmitReference(Asm->GetTempSymbol("exception", EHFrameInfo.Number),
LSDAEncoding);
else
Asm->OutStreamer.EmitIntValue(0, Size/*size*/, 0/*addrspace*/);
} else {
Asm->EmitULEB128(0, "Augmentation size");
}
// Indicate locations of function specific callee saved registers in frame.
Asm->EmitFrameMoves(EHFrameInfo.Moves, EHFuncBeginSym, true);
// On Darwin the linker honors the alignment of eh_frame, which means it
// must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
// get holes which confuse readers of eh_frame.
Asm->EmitAlignment(Asm->getTargetData().getPointerSize() == 4 ? 2 : 3);
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_end",
EHFrameInfo.Number));
// If the function is marked used, this table should be also. We cannot
// make the mark unconditional in this case, since retaining the table also
// retains the function in this case, and there is code around that depends
// on unused functions (calling undefined externals) being dead-stripped to
// link correctly. Yes, there really is.
if (MMI->isUsedFunction(EHFrameInfo.function))
if (Asm->MAI->hasNoDeadStrip())
Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
MCSA_NoDeadStrip);
}
Asm->OutStreamer.AddBlankLine();
}
/// EndModule - Emit all exception information that should come after the
/// content.
void DwarfTableException::EndModule() {
if (!Asm->MAI->isExceptionHandlingDwarf())
return;
if (!shouldEmitMovesModule && !shouldEmitTableModule)
return;
const std::vector<const Function*> &Personalities = MMI->getPersonalities();
for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
EmitCIE(Personalities[I], I);
for (std::vector<FunctionEHFrameInfo>::iterator
I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
EmitFDE(*I);
}
/// BeginFunction - Gather pre-function exception information. Assumes it's
/// being emitted immediately after the function entry point.
void DwarfTableException::BeginFunction(const MachineFunction *MF) {
shouldEmitTable = shouldEmitMoves = false;
// If any landing pads survive, we need an EH table.
shouldEmitTable = !MMI->getLandingPads().empty();
// See if we need frame move info.
shouldEmitMoves =
!Asm->MF->getFunction()->doesNotThrow() || UnwindTablesMandatory;
if (shouldEmitMoves || shouldEmitTable)
// Assumes in correct section after the entry point.
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
Asm->getFunctionNumber()));
shouldEmitTableModule |= shouldEmitTable;
shouldEmitMovesModule |= shouldEmitMoves;
}
/// EndFunction - Gather and emit post-function exception information.
///
void DwarfTableException::EndFunction() {
if (!shouldEmitMoves && !shouldEmitTable) return;
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
Asm->getFunctionNumber()));
// Record if this personality index uses a landing pad.
bool HasLandingPad = !MMI->getLandingPads().empty();
UsesLSDA[MMI->getPersonalityIndex()] |= HasLandingPad;
// Map all labels and get rid of any dead landing pads.
MMI->TidyLandingPads();
if (HasLandingPad)
EmitExceptionTable();
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
MCSymbol *FunctionEHSym =
Asm->GetSymbolWithGlobalValueBase(Asm->MF->getFunction(), ".eh",
TLOF.isFunctionEHFrameSymbolPrivate());
// Save EH frame information
EHFrames.
push_back(FunctionEHFrameInfo(FunctionEHSym,
Asm->getFunctionNumber(),
MMI->getPersonalityIndex(),
Asm->MF->getFrameInfo()->adjustsStack(),
!MMI->getLandingPads().empty(),
MMI->getFrameMoves(),
Asm->MF->getFunction()));
}
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