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ELF: Simplify Target::isSizeReloc and add comments. 

All non-trivial relocation decisions need explanations like this
to help readers understand not only how relocations are handled but
why they are handled these ways. This is a start.

llvm-svn: 257119
This commit is contained in:
Rui Ueyama 2016-01-08 00:13:23 +00:00
parent b626231a50
commit 3a7c2f6f44
3 changed files with 12 additions and 11 deletions
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9
lld/ELF/InputSection.cpp
View File

@ -219,8 +219,13 @@ void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd,
} else if (!Target->needsCopyRel(Type, *Body) &&
isa<SharedSymbol<ELFT>>(*Body)) {
continue;
} else if (Target->isTlsDynReloc(Type, *Body) ||
Target->isSizeDynReloc(Type, *Body)) {
} else if (Target->isTlsDynReloc(Type, *Body)) {
continue;
} else if (Target->isSizeReloc(Type) && canBePreempted(Body, false)) {
// A SIZE relocation is supposed to set a symbol size, but if a symbol
// can be preempted, the size at runtime may be different than link time.
// If that's the case, we leave the field alone rather than filling it
// with a possibly incorrect value.
continue;
} else if (Config->EMachine == EM_MIPS) {
if (Type == R_MIPS_HI16 && Body == Config->MipsGpDisp)

12
lld/ELF/Target.cpp
View File

@ -139,7 +139,7 @@ public:
uint8_t *PairedLoc = nullptr) const override;
bool isRelRelative(uint32_t Type) const override;
bool isTlsOptimized(unsigned Type, const SymbolBody *S) const override;
bool isSizeDynReloc(uint32_t Type, const SymbolBody &S) const override;
bool isSizeReloc(uint32_t Type) const override;
unsigned relocateTlsOptimize(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
uint64_t P, uint64_t SA,
const SymbolBody &S) const override;
@ -269,9 +269,7 @@ unsigned TargetInfo::getPltRefReloc(unsigned Type) const { return PCRelReloc; }
bool TargetInfo::isRelRelative(uint32_t Type) const { return true; }
bool TargetInfo::isSizeDynReloc(uint32_t Type, const SymbolBody &S) const {
return false;
}
bool TargetInfo::isSizeReloc(uint32_t Type) const { return false; }
unsigned TargetInfo::relocateTlsOptimize(uint8_t *Loc, uint8_t *BufEnd,
uint32_t Type, uint64_t P, uint64_t SA,
@ -722,10 +720,8 @@ bool X86_64TargetInfo::isRelRelative(uint32_t Type) const {
}
}
bool X86_64TargetInfo::isSizeDynReloc(uint32_t Type,
const SymbolBody &S) const {
return (Type == R_X86_64_SIZE32 || Type == R_X86_64_SIZE64) &&
canBePreempted(&S, false);
bool X86_64TargetInfo::isSizeReloc(uint32_t Type) const {
return Type == R_X86_64_SIZE32 || Type == R_X86_64_SIZE64;
}
bool X86_64TargetInfo::isTlsOptimized(unsigned Type,

2
lld/ELF/Target.h
View File

@ -58,7 +58,7 @@ public:
uint64_t GotEntryAddr, uint64_t PltEntryAddr,
int32_t Index, unsigned RelOff) const = 0;
virtual bool isRelRelative(uint32_t Type) const;
virtual bool isSizeDynReloc(uint32_t Type, const SymbolBody &S) const;
virtual bool isSizeReloc(uint32_t Type) const;
virtual bool relocNeedsDynRelative(unsigned Type) const { return false; }
virtual bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const = 0;
virtual bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const = 0;