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MC/Mach-O: Factor out isScatteredFixupFullyResolvedSimple predicate, and fix some corner cases.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98924 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Dunbar
2010-03-19 03:18:12 +00:00
parent 2386985663
commit 939f8d7ca2
2 changed files with 125 additions and 60 deletions
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67
lib/MC/MCAssembler.cpp
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@ -1010,6 +1010,44 @@ MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
MCAssembler::~MCAssembler() {
}
static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
const MCAsmFixup &Fixup,
const MCDataFragment *DF,
const MCValue Target,
const MCSection *BaseSection) {
// The effective fixup address is
// addr(atom(A)) + offset(A)
// - addr(atom(B)) - offset(B)
// - addr(<base symbol>) + <fixup offset from base symbol>
// and the offsets are not relocatable, so the fixup is fully resolved when
// addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
//
// The simple (Darwin, except on x86_64) way of dealing with this was to
// assume that any reference to a temporary symbol *must* be a temporary
// symbol in the same atom, unless the sections differ. Therefore, any PCrel
// relocation to a temporary symbol (in the same section) is fully
// resolved. This also works in conjunction with absolutized .set, which
// requires the compiler to use .set to absolutize the differences between
// symbols which the compiler knows to be assembly time constants, so we don't
// need to worry about consider symbol differences fully resolved.
// Non-relative fixups are only resolved if constant.
if (!BaseSection)
return Target.isAbsolute();
// Otherwise, relative fixups are only resolved if not a difference and the
// target is a temporary in the same section.
if (Target.isAbsolute() || Target.getSymB())
return false;
const MCSymbol *A = &Target.getSymA()->getSymbol();
if (!A->isTemporary() || !A->isInSection() ||
&A->getSection() != BaseSection)
return false;
return true;
}
bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
// Non-temporary labels should always be visible to the linker.
if (!SD->getSymbol().isTemporary())
@ -1036,34 +1074,33 @@ bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout, MCAsmFixup &Fixup,
Value = Target.getConstant();
// FIXME: This "resolved" check isn't quite right. The assumption is that if
// we have a PCrel access to a temporary, then that temporary is in the same
// atom, and so the value is resolved. We need explicit atom's to implement
// this more precisely.
bool IsResolved = true, IsPCRel = isFixupKindPCRel(Fixup.Kind);
if (const MCSymbolRefExpr *A = Target.getSymA()) {
if (A->getSymbol().isDefined())
Value += getSymbolData(A->getSymbol()).getAddress();
else
IsResolved = false;
// With scattered symbols, we assume anything that isn't a PCrel temporary
// access can have an arbitrary value.
if (getBackend().hasScatteredSymbols() &&
(!IsPCRel || !A->getSymbol().isTemporary()))
IsResolved = false;
}
if (const MCSymbolRefExpr *B = Target.getSymB()) {
if (B->getSymbol().isDefined())
Value -= getSymbolData(B->getSymbol()).getAddress();
else
IsResolved = false;
}
// With scattered symbols, we assume anything that isn't a PCrel temporary
// access can have an arbitrary value.
if (getBackend().hasScatteredSymbols() &&
(!IsPCRel || !B->getSymbol().isTemporary()))
IsResolved = false;
// If we are using scattered symbols, determine whether this value is actually
// resolved; scattering may cause atoms to move.
if (IsResolved && getBackend().hasScatteredSymbols()) {
if (getBackend().hasReliableSymbolDifference()) {
llvm_report_error("FIXME: Not yet implemented");
} else {
const MCSection *BaseSection = 0;
if (IsPCRel)
BaseSection = &DF->getParent()->getSection();
IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, DF, Target,
BaseSection);
}
}
if (IsPCRel)