[llvm] r267307 - [MC/ELF] Implement support for GOTPCRELX/REX_GOTPCRELX.
Rafael Espíndola via llvm-commits
llvm-commits at lists.llvm.org
Sun Apr 24 08:44:00 PDT 2016
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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