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[mips] Make TTypeEncoding indirect to allow .eh_frame to be read-only.

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Summary:
Following on from r209907 which made personality encodings indirect, do the
same for TType encodings. This fixes the case where a try/catch block needs
to generate references to, for example, std::exception in the
.gcc_except_table.

This commit uses DW_EH_PE_sdata8 for N64 as far as is possible at the moment.
However, it is possible to end up with DW_EH_PE_sdata4 when a TargetMachine is
not available. There's no risk of issues with inconsistency here since the
tables are self describing but it does mean there is a small chance of the
PC-relative offset being out of range for particularly large programs.

Reviewers: petarj

Reviewed By: petarj

Subscribers: srhines, joerg, tberghammer, llvm-commits

Differential Revision: http://reviews.llvm.org/D9669

llvm-svn: 238190
This commit is contained in:
Daniel Sanders 2015-05-26 10:19:18 +00:00
parent 1160fba49a
commit adc4fb19a2
5 changed files with 48 additions and 11 deletions
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2
include/llvm/MC/MCObjectFileInfo.h
View File

@ -352,6 +352,8 @@ private:
///
void InitEHFrameSection();
virtual unsigned SelectMipsTTypeEncoding() const;
public:
const Triple &getTargetTriple() const { return TT; }
};

17
lib/MC/MCObjectFileInfo.cpp
View File

@ -324,10 +324,13 @@ void MCObjectFileInfo::InitELFMCObjectFileInfo(Triple T) {
case Triple::mipsel:
case Triple::mips64:
case Triple::mips64el:
// MIPS uses indirect pointer to refer personality functions, so that the
// eh_frame section can be read-only. DW.ref.personality will be generated
// for relocation.
// 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;
TTypeEncoding = SelectMipsTTypeEncoding();
// We don't support PC-relative LSDA references in GAS so we use the default
// DW_EH_PE_absptr for those.
break;
case Triple::ppc64:
case Triple::ppc64le:
@ -793,3 +796,11 @@ void MCObjectFileInfo::InitEHFrameSection() {
COFF::IMAGE_SCN_MEM_WRITE,
SectionKind::getDataRel());
}
unsigned MCObjectFileInfo::SelectMipsTTypeEncoding() const {
// FIXME: The N64 ABI ought to use DW_EH_PE_sdata8 but we can't
// identify N64 from just a triple. We currently fix this by
// overriding this function in MipsTargetObjectFile.
return dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
}

8
lib/Target/Mips/MipsTargetObjectFile.cpp
View File

@ -37,6 +37,7 @@ ExternSData("mextern-sdata", cl::Hidden,
cl::init(true));
void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
this->TM = &static_cast<const MipsTargetMachine &>(TM);
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);
@ -45,7 +46,6 @@ void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
SmallBSSSection = getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
this->TM = &static_cast<const MipsTargetMachine &>(TM);
}
// A address must be loaded from a small section if its size is less than the
@ -146,3 +146,9 @@ MipsTargetObjectFile::getSectionForConstant(SectionKind Kind,
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::getSectionForConstant(Kind, C);
}
unsigned MipsTargetObjectFile::SelectMipsTTypeEncoding() const {
return dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
(TM->getABI().ArePtrs64bit() ? dwarf::DW_EH_PE_sdata8
: dwarf::DW_EH_PE_sdata4);
}

2
lib/Target/Mips/MipsTargetObjectFile.h
View File

@ -41,6 +41,8 @@ class MipsTargetMachine;
MCSection *getSectionForConstant(SectionKind Kind,
const Constant *C) const override;
unsigned SelectMipsTTypeEncoding() const override;
};
} // end namespace llvm

30
test/CodeGen/Mips/ehframe-indirect.ll
View File

@ -1,9 +1,11 @@
; RUN: llc -mtriple=mipsel-linux-gnu < %s | FileCheck -check-prefix=ALL -check-prefix=O32 %s
; RUN: llc -mtriple=mipsel-linux-android < %s | FileCheck -check-prefix=ALL -check-prefix=O32 %s
; RUN: llc -mtriple=mips64el-linux-gnu -target-abi=n32 < %s | FileCheck -check-prefix=ALL -check-prefix=N32 %s
; RUN: llc -mtriple=mips64el-linux-android -target-abi=n32 < %s | FileCheck -check-prefix=ALL -check-prefix=N32 %s
; RUN: llc -mtriple=mips64el-linux-gnu < %s | FileCheck -check-prefix=ALL -check-prefix=N64 %s
; RUN: llc -mtriple=mips64el-linux-android < %s | FileCheck -check-prefix=ALL -check-prefix=N64 %s
; RUN: llc -mtriple=mipsel-linux-gnu < %s -asm-verbose | FileCheck -check-prefix=ALL -check-prefix=O32 %s
; RUN: llc -mtriple=mipsel-linux-android < %s -asm-verbose | FileCheck -check-prefix=ALL -check-prefix=O32 %s
; RUN: llc -mtriple=mips64el-linux-gnu -target-abi=n32 < %s -asm-verbose | FileCheck -check-prefix=ALL -check-prefix=N32 %s
; RUN: llc -mtriple=mips64el-linux-android -target-abi=n32 < %s -asm-verbose | FileCheck -check-prefix=ALL -check-prefix=N32 %s
; RUN: llc -mtriple=mips64el-linux-gnu < %s -asm-verbose | FileCheck -check-prefix=ALL -check-prefix=N64 %s
; RUN: llc -mtriple=mips64el-linux-android < %s -asm-verbose | FileCheck -check-prefix=ALL -check-prefix=N64 %s
@_ZTISt9exception = external constant i8*
define i32 @main() {
; ALL: .cfi_startproc
@ -16,7 +18,9 @@ entry:
lpad:
%0 = landingpad { i8*, i32 } personality i8*
bitcast (i32 (...)* @__gxx_personality_v0 to i8*) catch i8* null
bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
catch i8* null
catch i8* bitcast (i8** @_ZTISt9exception to i8*)
ret i32 0
cont:
@ -28,6 +32,18 @@ declare i32 @__gxx_personality_v0(...)
declare void @foo()
; ALL: GCC_except_table{{[0-9]+}}:
; O32: .byte 155 # @TType Encoding = indirect pcrel sdata4
; N32: .byte 155 # @TType Encoding = indirect pcrel sdata4
; N64: .byte 156 # @TType Encoding = indirect pcrel sdata8
; ALL: $[[PC_LABEL:tmp[0-9]+]]:
; O32: .4byte ($_ZTISt9exception.DW.stub)-($[[PC_LABEL]])
; N32: .4byte ($_ZTISt9exception.DW.stub)-($[[PC_LABEL]])
; N64: .8byte ($_ZTISt9exception.DW.stub)-($[[PC_LABEL]])
; ALL: $_ZTISt9exception.DW.stub:
; O32: .4byte _ZTISt9exception
; N32: .4byte _ZTISt9exception
; N64: .8byte _ZTISt9exception
; ALL: .hidden DW.ref.__gxx_personality_v0
; ALL: .weak DW.ref.__gxx_personality_v0
; ALL: .section .data.DW.ref.__gxx_personality_v0,"aGw",@progbits,DW.ref.__gxx_personality_v0,comdat