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[ELF][ARM] Add getPCBias()

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ThunkCreator::getThunk and ThunkCreator::normalizeExistingThunk
currently assume that the implicit addends are -8 for ARM and -4 for
Thumb. In D70637, ThunkCreator::getThunk will need to take care of the
relocation addend explicitly.

Add the utility function getPCBias() as a prerequisite so that the getThunk change in D70637
can be more general.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D70690
This commit is contained in:
Fangrui Song 2019-11-25 11:02:56 -08:00
parent a048bf87fb
commit 3d9b1128d6
1 changed files with 18 additions and 2 deletions
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20
lld/ELF/Relocations.cpp
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@ -1763,6 +1763,19 @@ static bool isThunkSectionCompatible(InputSection *source,
return true;
}
static int64_t getPCBias(RelType type) {
if (config->emachine != EM_ARM)
return 0;
switch (type) {
case R_ARM_THM_JUMP19:
case R_ARM_THM_JUMP24:
case R_ARM_THM_CALL:
return 4;
default:
return 8;
}
}
std::pair<Thunk *, bool> ThunkCreator::getThunk(InputSection *isec,
Relocation &rel, uint64_t src) {
std::vector<Thunk *> *thunkVec = nullptr;
@ -1779,7 +1792,9 @@ std::pair<Thunk *, bool> ThunkCreator::getThunk(InputSection *isec,
for (Thunk *t : *thunkVec)
if (isThunkSectionCompatible(isec, t->getThunkTargetSym()->section) &&
t->isCompatibleWith(*isec, rel) &&
target->inBranchRange(rel.type, src, t->getThunkTargetSym()->getVA()))
target->inBranchRange(rel.type, src,
t->getThunkTargetSym()->getVA(rel.addend) +
getPCBias(rel.type)))
return std::make_pair(t, false);
// No existing compatible Thunk in range, create a new one
@ -1794,7 +1809,8 @@ std::pair<Thunk *, bool> ThunkCreator::getThunk(InputSection *isec,
// relocation back to its original non-Thunk target.
bool ThunkCreator::normalizeExistingThunk(Relocation &rel, uint64_t src) {
if (Thunk *t = thunks.lookup(rel.sym)) {
if (target->inBranchRange(rel.type, src, rel.sym->getVA()))
if (target->inBranchRange(rel.type, src,
rel.sym->getVA(rel.addend) + getPCBias(rel.type)))
return true;
rel.sym = &t->destination;
if (rel.sym->isInPlt())