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[MC] Move EH DWARF encodings from MC to CodeGen, NFC
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Summary:
The TType encoding, LSDA encoding, and personality encoding are all
passed explicitly by CodeGen to the assembler through .cfi_* directives,
so only the AsmPrinter needs to know about them.

The FDE CFI encoding however, controls the encoding of the label
implicitly created by the .cfi_startproc directive. That directive seems
to be special in that it doesn't take an encoding, so the assembler just
has to know how to encode one DSO-local label reference from .eh_frame
to .text.

As a result, it looks like MC will continue to have to know when the
large code model is in use. Perhaps we could invent a '.cfi_startproc
[large]' flag so that this knowledge doesn't need to pollute the
assembler.

Reviewers: davide, lliu0, JDevlieghere

Subscribers: hiraditya, fedor.sergeev, llvm-commits

Differential Revision: https://reviews.llvm.org/D50533

llvm-svn: 339397
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@rnk
rnk committed Aug 9, 2018
1 parent c6944f7 commit fce7f73
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Showing 5 changed files with 179 additions and 166 deletions.
14 changes: 5 additions & 9 deletions llvm/include/llvm/MC/MCObjectFileInfo.h
View file
Expand Up @@ -42,12 +42,11 @@ class MCObjectFileInfo {
/// dwarf unwind.
bool OmitDwarfIfHaveCompactUnwind;

/// PersonalityEncoding, LSDAEncoding, TTypeEncoding - Some encoding values
/// for EH.
unsigned PersonalityEncoding;
unsigned LSDAEncoding;
unsigned FDECFIEncoding;
unsigned TTypeEncoding;
/// FDE CFI encoding. Controls the encoding of the begin label in the
/// .eh_frame section. Unlike the LSDA encoding, personality encoding, and
/// type encodings, this is something that the assembler just "knows" about
/// its target
unsigned FDECFIEncoding = 0;

/// Compact unwind encoding indicating that we should emit only an EH frame.
unsigned CompactUnwindDwarfEHFrameOnly;
Expand Down Expand Up @@ -226,10 +225,7 @@ class MCObjectFileInfo {
return CommDirectiveSupportsAlignment;
}

unsigned getPersonalityEncoding() const { return PersonalityEncoding; }
unsigned getLSDAEncoding() const { return LSDAEncoding; }
unsigned getFDEEncoding() const { return FDECFIEncoding; }
unsigned getTTypeEncoding() const { return TTypeEncoding; }

unsigned getCompactUnwindDwarfEHFrameOnly() const {
return CompactUnwindDwarfEHFrameOnly;
Expand Down
10 changes: 10 additions & 0 deletions llvm/include/llvm/Target/TargetLoweringObjectFile.h
View file
Expand Up @@ -47,6 +47,12 @@ class TargetLoweringObjectFile : public MCObjectFileInfo {
bool SupportGOTPCRelWithOffset = true;
bool SupportDebugThreadLocalLocation = true;

/// PersonalityEncoding, LSDAEncoding, TTypeEncoding - Some encoding values
/// for EH.
unsigned PersonalityEncoding = 0;
unsigned LSDAEncoding = 0;
unsigned TTypeEncoding = 0;

/// This section contains the static constructor pointer list.
MCSection *StaticCtorSection = nullptr;

Expand Down Expand Up @@ -136,6 +142,10 @@ class TargetLoweringObjectFile : public MCObjectFileInfo {
const TargetMachine &TM,
MachineModuleInfo *MMI) const;

unsigned getPersonalityEncoding() const { return PersonalityEncoding; }
unsigned getLSDAEncoding() const { return LSDAEncoding; }
unsigned getTTypeEncoding() const { return TTypeEncoding; }

const MCExpr *getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding,
MCStreamer &Streamer) const;

Expand Down
156 changes: 156 additions & 0 deletions llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View file
Expand Up @@ -95,6 +95,156 @@ void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
const TargetMachine &TgtM) {
TargetLoweringObjectFile::Initialize(Ctx, TgtM);
TM = &TgtM;

bool Large = TgtM.getCodeModel() == CodeModel::Large;

switch (TgtM.getTargetTriple().getArch()) {
case Triple::arm:
case Triple::armeb:
case Triple::thumb:
case Triple::thumbeb:
if (Ctx.getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
break;
// Fallthrough if not using EHABI
LLVM_FALLTHROUGH;
case Triple::ppc:
case Triple::x86:
PersonalityEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_indirect |
dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
LSDAEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
TTypeEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
break;
case Triple::x86_64:
if (isPositionIndependent()) {
PersonalityEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
(Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
LSDAEncoding = dwarf::DW_EH_PE_pcrel |
(Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
(Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
} else {
PersonalityEncoding =
Large ? dwarf::DW_EH_PE_absptr : dwarf::DW_EH_PE_udata4;
LSDAEncoding = Large ? dwarf::DW_EH_PE_absptr : dwarf::DW_EH_PE_udata4;
TTypeEncoding = Large ? dwarf::DW_EH_PE_absptr : dwarf::DW_EH_PE_udata4;
}
break;
case Triple::hexagon:
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
if (isPositionIndependent()) {
PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
LSDAEncoding |= dwarf::DW_EH_PE_pcrel;
TTypeEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
}
break;
case Triple::aarch64:
case Triple::aarch64_be:
// The small model guarantees static code/data size < 4GB, but not where it
// will be in memory. Most of these could end up >2GB away so even a signed
// pc-relative 32-bit address is insufficient, theoretically.
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata8;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata8;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::lanai:
LSDAEncoding = dwarf::DW_EH_PE_absptr;
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
break;
case Triple::mips:
case Triple::mipsel:
case Triple::mips64:
case Triple::mips64el:
// MIPS uses indirect pointer to refer personality functions and types, so
// that the eh_frame section can be read-only. DW.ref.personality will be
// generated for relocation.
PersonalityEncoding = dwarf::DW_EH_PE_indirect;
// FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
// identify N64 from just a triple.
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
// We don't support PC-relative LSDA references in GAS so we use the default
// DW_EH_PE_absptr for those.

// FreeBSD must be explicit about the data size and using pcrel since it's
// assembler/linker won't do the automatic conversion that the Linux tools
// do.
if (TgtM.getTargetTriple().isOSFreeBSD()) {
PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
}
break;
case Triple::ppc64:
case Triple::ppc64le:
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_udata8;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_udata8;
break;
case Triple::sparcel:
case Triple::sparc:
if (isPositionIndependent()) {
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
LSDAEncoding = dwarf::DW_EH_PE_absptr;
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::sparcv9:
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::systemz:
// All currently-defined code models guarantee that 4-byte PC-relative
// values will be in range.
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
default:
break;
}
}

void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
Expand Down Expand Up @@ -684,6 +834,12 @@ void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
MachO::S_MOD_TERM_FUNC_POINTERS,
SectionKind::getData());
}

PersonalityEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel;
TTypeEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
}

void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
Expand Down

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