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MC: Emit symbols for R_X86_64_PLT32 relocation pointing to symbols with non-zero values. #138795

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MC: Emit symbols for R_X86_64_PLT32 relocation pointing to symbols with non-zero values. #138795

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e6c93d7
[𝘀𝗽𝗿] initial version
pcc May 7, 2025
08fc3d8
Rebase
pcc May 7, 2025
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3 changes: 2 additions & 1 deletion llvm/include/llvm/MC/MCELFObjectWriter.h
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Expand Up @@ -88,7 +88,8 @@ class MCELFObjectTargetWriter : public MCObjectTargetWriter {
virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const = 0;

virtual bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
virtual bool needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &Val, const MCSymbol &Sym,
unsigned Type) const;

virtual void sortRelocs(const MCAssembler &Asm,
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2 changes: 1 addition & 1 deletion llvm/lib/MC/ELFObjectWriter.cpp
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Expand Up @@ -1303,7 +1303,7 @@ bool ELFObjectWriter::useSectionSymbol(const MCAssembler &Asm,
if (Asm.isThumbFunc(Sym))
return false;

return !TargetObjectWriter->needsRelocateWithSymbol(Val, *Sym, Type);
return !TargetObjectWriter->needsRelocateWithSymbol(Asm, Val, *Sym, Type);
}

bool ELFObjectWriter::checkRelocation(MCContext &Ctx, SMLoc Loc,
Expand Down
3 changes: 2 additions & 1 deletion llvm/lib/MC/MCELFObjectTargetWriter.cpp
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Expand Up @@ -17,7 +17,8 @@ MCELFObjectTargetWriter::MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_,
: OSABI(OSABI_), ABIVersion(ABIVersion_), EMachine(EMachine_),
HasRelocationAddend(HasRelocationAddend_), Is64Bit(Is64Bit_) {}

bool MCELFObjectTargetWriter::needsRelocateWithSymbol(const MCValue &,
bool MCELFObjectTargetWriter::needsRelocateWithSymbol(const MCAssembler &,
const MCValue &,
const MCSymbol &,
unsigned Type) const {
return false;
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
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Expand Up @@ -38,7 +38,8 @@ class AArch64ELFObjectWriter : public MCELFObjectTargetWriter {
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
bool IsILP32;
};
Expand Down Expand Up @@ -534,7 +535,8 @@ unsigned AArch64ELFObjectWriter::getRelocType(MCContext &Ctx,
llvm_unreachable("Unimplemented fixup -> relocation");
}

bool AArch64ELFObjectWriter::needsRelocateWithSymbol(const MCValue &Val,
bool AArch64ELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &Val,
const MCSymbol &,
unsigned) const {
// For memory-tagged symbols, ensure that the relocation uses the symbol. For
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
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Expand Up @@ -39,7 +39,8 @@ namespace {
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;

bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};

Expand All @@ -50,7 +51,8 @@ ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
ELF::EM_ARM,
/*HasRelocationAddend*/ false) {}

bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCValue &,
bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &,
const MCSymbol &,
unsigned Type) const {
// FIXME: This is extremely conservative. This really needs to use an
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFObjectWriter.cpp
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Expand Up @@ -29,7 +29,8 @@ class CSKYELFObjectWriter : public MCELFObjectTargetWriter {

unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};

Expand Down Expand Up @@ -167,7 +168,8 @@ unsigned CSKYELFObjectWriter::getRelocType(MCContext &Ctx,
}
}

bool CSKYELFObjectWriter::needsRelocateWithSymbol(const MCValue &V,
bool CSKYELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &V,
const MCSymbol &,
unsigned Type) const {
switch (V.getSpecifier()) {
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/Lanai/MCTargetDesc/LanaiELFObjectWriter.cpp
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Expand Up @@ -26,7 +26,8 @@ class LanaiELFObjectWriter : public MCELFObjectTargetWriter {
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};

Expand Down Expand Up @@ -72,7 +73,8 @@ unsigned LanaiELFObjectWriter::getRelocType(MCContext & /*Ctx*/,
return Type;
}

bool LanaiELFObjectWriter::needsRelocateWithSymbol(const MCValue &,
bool LanaiELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &,
const MCSymbol &,
unsigned Type) const {
switch (Type) {
Expand Down
3 changes: 2 additions & 1 deletion llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchELFObjectWriter.cpp
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Expand Up @@ -26,7 +26,8 @@ class LoongArchELFObjectWriter : public MCELFObjectTargetWriter {

~LoongArchELFObjectWriter() override;

bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override {
return EnableRelax;
}
Expand Down
12 changes: 7 additions & 5 deletions llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
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Expand Up @@ -50,7 +50,8 @@ class MipsELFObjectWriter : public MCELFObjectTargetWriter {

unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
void sortRelocs(const MCAssembler &Asm,
std::vector<ELFRelocationEntry> &Relocs) override;
Expand Down Expand Up @@ -444,15 +445,16 @@ void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm,
Relocs[CopyTo++] = R.R;
}

bool MipsELFObjectWriter::needsRelocateWithSymbol(const MCValue &Val,
bool MipsELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const {
// If it's a compound relocation for N64 then we need the relocation if any
// sub-relocation needs it.
if (!isUInt<8>(Type))
return needsRelocateWithSymbol(Val, Sym, Type & 0xff) ||
needsRelocateWithSymbol(Val, Sym, (Type >> 8) & 0xff) ||
needsRelocateWithSymbol(Val, Sym, (Type >> 16) & 0xff);
return needsRelocateWithSymbol(Asm, Val, Sym, Type & 0xff) ||
needsRelocateWithSymbol(Asm, Val, Sym, (Type >> 8) & 0xff) ||
needsRelocateWithSymbol(Asm, Val, Sym, (Type >> 16) & 0xff);

switch (Type) {
default:
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
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Expand Up @@ -28,7 +28,8 @@ namespace {
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;

bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};
}
Expand Down Expand Up @@ -488,7 +489,8 @@ unsigned PPCELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
return Type;
}

bool PPCELFObjectWriter::needsRelocateWithSymbol(const MCValue &,
bool PPCELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &,
const MCSymbol &Sym,
unsigned Type) const {
switch (Type) {
Expand Down
3 changes: 2 additions & 1 deletion llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
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Expand Up @@ -27,7 +27,8 @@ class RISCVELFObjectWriter : public MCELFObjectTargetWriter {

// Return true if the given relocation must be with a symbol rather than
// section plus offset.
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override {
// TODO: this is very conservative, update once RISC-V psABI requirements
// are clarified.
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
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Expand Up @@ -33,7 +33,8 @@ namespace {
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;

bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};
}
Expand Down Expand Up @@ -144,7 +145,8 @@ unsigned SparcELFObjectWriter::getRelocType(MCContext &Ctx,
return ELF::R_SPARC_NONE;
}

bool SparcELFObjectWriter::needsRelocateWithSymbol(const MCValue &,
bool SparcELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &,
const MCSymbol &,
unsigned Type) const {
switch (Type) {
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/SystemZ/MCTargetDesc/SystemZELFObjectWriter.cpp
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Expand Up @@ -34,7 +34,8 @@ class SystemZELFObjectWriter : public MCELFObjectTargetWriter {
// Override MCELFObjectTargetWriter.
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};

Expand Down Expand Up @@ -215,7 +216,8 @@ unsigned SystemZELFObjectWriter::getRelocType(MCContext &Ctx,
}
}

bool SystemZELFObjectWriter::needsRelocateWithSymbol(const MCValue &V,
bool SystemZELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &V,
const MCSymbol &Sym,
unsigned Type) const {
switch (V.getSpecifier()) {
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/VE/MCTargetDesc/VEELFObjectWriter.cpp
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Expand Up @@ -32,7 +32,8 @@ class VEELFObjectWriter : public MCELFObjectTargetWriter {
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;

bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};
} // namespace
Expand Down Expand Up @@ -146,7 +147,8 @@ unsigned VEELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
return ELF::R_VE_NONE;
}

bool VEELFObjectWriter::needsRelocateWithSymbol(const MCValue &,
bool VEELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &,
const MCSymbol &,
unsigned Type) const {
switch (Type) {
Expand Down
10 changes: 7 additions & 3 deletions llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
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Expand Up @@ -11,6 +11,7 @@
#include "MCTargetDesc/X86MCTargetDesc.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
Expand All @@ -33,7 +34,8 @@ class X86ELFObjectWriter : public MCELFObjectTargetWriter {
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};

Expand Down Expand Up @@ -386,7 +388,8 @@ unsigned X86ELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
return getRelocType32(Ctx, Fixup.getLoc(), Specifier, RelType, IsPCRel, Kind);
}

bool X86ELFObjectWriter::needsRelocateWithSymbol(const MCValue &V,
bool X86ELFObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &V,
const MCSymbol &Sym,
unsigned Type) const {
switch (V.getSpecifier()) {
Expand All @@ -396,7 +399,8 @@ bool X86ELFObjectWriter::needsRelocateWithSymbol(const MCValue &V,
case X86MCExpr::VK_GOTPCREL_NORELAX:
return true;
default:
return false;
return Type == ELF::R_X86_64_PLT32 &&
(Asm.getFragmentOffset(*Sym.getFragment()) + Sym.getOffset()) != 0;
}
}

Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/Target/Xtensa/MCTargetDesc/XtensaELFObjectWriter.cpp
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Expand Up @@ -32,7 +32,8 @@ class XtensaObjectWriter : public MCELFObjectTargetWriter {
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCValue &Val, const MCSymbol &Sym,
bool needsRelocateWithSymbol(const MCAssembler &Asm, const MCValue &Val,
const MCSymbol &Sym,
unsigned Type) const override;
};
} // namespace
Expand Down Expand Up @@ -60,7 +61,8 @@ llvm::createXtensaObjectWriter(uint8_t OSABI, bool IsLittleEndian) {
return std::make_unique<XtensaObjectWriter>(OSABI);
}

bool XtensaObjectWriter::needsRelocateWithSymbol(const MCValue &,
bool XtensaObjectWriter::needsRelocateWithSymbol(const MCAssembler &Asm,
const MCValue &,
const MCSymbol &,
unsigned Type) const {
return false;
Expand Down
14 changes: 14 additions & 0 deletions llvm/test/MC/ELF/plt-temporary.s
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@@ -0,0 +1,14 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -r - | FileCheck %s

// Test that this produces a R_X86_64_PLT32 pointing to .Lfoo
// instead of the section symbol.

.section .text.a,"ax",@progbits
jmp .Lfoo

.text
ret
.Lfoo:
ret

// CHECK: R_X86_64_PLT32 .Lfoo 0xFFFFFFFFFFFFFFFC