[llvm] r267307 - [MC/ELF] Implement support for GOTPCRELX/REX_GOTPCRELX.
Rafael Espíndola via llvm-commits
llvm-commits at lists.llvm.org
Sun Apr 24 11:13:13 PDT 2016
oops, just noticed you added it in r267308.
Thanks,
Rafael
On 24 April 2016 at 11:44, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
> Please add a case where we produce R_X86_64_GOTPCREL even when given the
> command line.
>
> Cheers,
> Rafael
>
> On Apr 23, 2016 9:09 PM, "Davide Italiano via llvm-commits"
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: davide
>> Date: Sat Apr 23 20:03:57 2016
>> New Revision: 267307
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=267307&view=rev
>> Log:
>> [MC/ELF] Implement support for GOTPCRELX/REX_GOTPCRELX.
>>
>> The option to control the emission of the new relocations
>> is -relax-relocations (blatantly copied from GNU as).
>> It can't be enabled by default because it breaks relatively
>> recent versions of ld.bfd/ld.gold (late 2015).
>>
>> Added:
>> llvm/trunk/test/MC/ELF/got-relaxed.s
>> Modified:
>> llvm/trunk/include/llvm/MC/MCAsmInfo.h
>> llvm/trunk/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
>> llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp
>>
>> Modified: llvm/trunk/include/llvm/MC/MCAsmInfo.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCAsmInfo.h?rev=267307&r1=267306&r2=267307&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/include/llvm/MC/MCAsmInfo.h (original)
>> +++ llvm/trunk/include/llvm/MC/MCAsmInfo.h Sat Apr 23 20:03:57 2016
>> @@ -363,6 +363,10 @@ protected:
>> /// expressions as logical rather than arithmetic.
>> bool UseLogicalShr;
>>
>> + // If true, emit GOTPCRELX/REX_GOTPCRELX instead of GOTPCREL, on
>> + // X86_64 ELF.
>> + bool RelaxELFRelocations;
>> +
>> public:
>> explicit MCAsmInfo();
>> virtual ~MCAsmInfo();
>> @@ -568,6 +572,8 @@ public:
>> }
>>
>> bool shouldUseLogicalShr() const { return UseLogicalShr; }
>> +
>> + bool canRelaxRelocations() const { return RelaxELFRelocations; }
>> };
>> }
>>
>>
>> Modified: llvm/trunk/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp?rev=267307&r1=267306&r2=267307&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
>> (original)
>> +++ llvm/trunk/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp Sat Apr
>> 23 20:03:57 2016
>> @@ -9,6 +9,7 @@
>>
>> #include "MCTargetDesc/X86FixupKinds.h"
>> #include "MCTargetDesc/X86MCTargetDesc.h"
>> +#include "llvm/MC/MCAsmInfo.h"
>> #include "llvm/MC/MCContext.h"
>> #include "llvm/MC/MCELFObjectWriter.h"
>> #include "llvm/MC/MCExpr.h"
>> @@ -84,10 +85,10 @@ static void checkIs32(MCContext &Ctx, SM
>> "32 bit reloc applied to a field with a different
>> size");
>> }
>>
>> -static unsigned getRelocType64(MCContext &Ctx, const MCFixup &Fixup,
>> +static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
>> MCSymbolRefExpr::VariantKind Modifier,
>> - X86_64RelType Type, bool IsPCRel) {
>> - SMLoc Loc = Fixup.getLoc();
>> + X86_64RelType Type, bool IsPCRel,
>> + unsigned Kind) {
>> switch (Modifier) {
>> default:
>> llvm_unreachable("Unimplemented");
>> @@ -173,7 +174,19 @@ static unsigned getRelocType64(MCContext
>> return ELF::R_X86_64_PLT32;
>> case MCSymbolRefExpr::VK_GOTPCREL:
>> checkIs32(Ctx, Loc, Type);
>> - return ELF::R_X86_64_GOTPCREL;
>> + // Older versions of ld.bfd/ld.gold/lld
>> + // do not support GOTPCRELX/REX_GOTPCRELX,
>> + // and we want to keep back-compatibility.
>> + if (!Ctx.getAsmInfo()->canRelaxRelocations())
>> + return ELF::R_X86_64_GOTPCREL;
>> + switch (Kind) {
>> + default:
>> + return ELF::R_X86_64_GOTPCREL;
>> + case X86::reloc_riprel_4byte:
>> + return ELF::R_X86_64_GOTPCRELX;
>> + case X86::reloc_riprel_4byte_movq_load:
>> + return ELF::R_X86_64_REX_GOTPCRELX;
>> + }
>> }
>> }
>>
>> @@ -259,7 +272,8 @@ unsigned X86ELFObjectWriter::getRelocTyp
>> MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
>> X86_64RelType Type = getType64(Fixup.getKind(), Modifier, IsPCRel);
>> if (getEMachine() == ELF::EM_X86_64)
>> - return getRelocType64(Ctx, Fixup, Modifier, Type, IsPCRel);
>> + return getRelocType64(Ctx, Fixup.getLoc(), Modifier, Type, IsPCRel,
>> + Fixup.getKind());
>>
>> assert((getEMachine() == ELF::EM_386 || getEMachine() == ELF::EM_IAMCU)
>> &&
>> "Unsupported ELF machine type.");
>>
>> Modified: llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp?rev=267307&r1=267306&r2=267307&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp (original)
>> +++ llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp Sat Apr 23
>> 20:03:57 2016
>> @@ -35,6 +35,10 @@ AsmWriterFlavor("x86-asm-syntax", cl::in
>> clEnumValEnd));
>>
>> static cl::opt<bool>
>> +RelaxELFRel("relax-relocations", cl::init(false),
>> + cl::desc("Emit R_X86_64_GOTPCRELX instead of R_X86_64_GOTPCREL"));
>> +
>> +static cl::opt<bool>
>> MarkedJTDataRegions("mark-data-regions", cl::init(false),
>> cl::desc("Mark code section jump table data regions."),
>> cl::Hidden);
>> @@ -111,6 +115,8 @@ X86ELFMCAsmInfo::X86ELFMCAsmInfo(const T
>> // Always enable the integrated assembler by default.
>> // Clang also enabled it when the OS is Solaris but that is redundant
>> here.
>> UseIntegratedAssembler = true;
>> +
>> + RelaxELFRelocations = RelaxELFRel;
>> }
>>
>> const MCExpr *
>>
>> Added: llvm/trunk/test/MC/ELF/got-relaxed.s
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/got-relaxed.s?rev=267307&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/MC/ELF/got-relaxed.s (added)
>> +++ llvm/trunk/test/MC/ELF/got-relaxed.s Sat Apr 23 20:03:57 2016
>> @@ -0,0 +1,18 @@
>> +// RUN: llvm-mc -filetype=obj -relax-relocations -triple
>> x86_64-pc-linux-gnu %s -o - | llvm-readobj -r -t | FileCheck %s
>> +
>> +// Test that this produces the correct relaxed relocations.
>> +
>> + movl foo at GOT, %eax
>> + movl foo at GOTPCREL(%rip), %eax
>> + movq foo at GOTPCREL(%rip), %rax
>> +
>> +// CHECK: Relocations [
>> +// CHECK: Section ({{[^ ]+}}) .rela.text {
>> +// CHECK-NEXT: 0x{{[^ ]+}} R_X86_64_GOT32 foo 0x{{[^ ]+}}
>> +// CHECK-NEXT: 0x{{[^ ]+}} R_X86_64_GOTPCRELX foo 0x{{[^ ]+}}
>> +// CHECK-NEXT: 0x{{[^ ]+}} R_X86_64_REX_GOTPCRELX foo 0x{{[^ ]+}}
>> +// CHECK-NEXT: }
>> +// CHECK-NEXT: ]
>> +
>> +// CHECK: Symbols [
>> +// CHECK-NOT: _GLOBAL_OFFSET_TABLE_
>>
>>
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