- // x86_64 almost always uses external relocations, except when there is no
- // symbol to use as a base address (a local symbol with no preceeding
- // non-local symbol).
- if (Base) {
- Index = Base->getIndex();
- IsExtern = 1;
-
- // Add the local offset, if needed.
- if (Base != &SD)
- Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base);
- } else if (Symbol->isInSection()) {
- // The index is the section ordinal (1-based).
- Index = SD.getFragment()->getParent()->getOrdinal() + 1;
- IsExtern = 0;
- Value += Layout.getSymbolAddress(&SD);
-
- if (IsPCRel)
- Value -= FixupAddress + (1 << Log2Size);
- } else {
- report_fatal_error("unsupported relocation of undefined symbol '" +
- Symbol->getName() + "'");
- }
-
- MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
- if (IsPCRel) {
- if (IsRIPRel) {
- if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
- // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
- // rewrite the movq to an leaq at link time if the symbol ends up in
- // the same linkage unit.
- if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
- Type = RIT_X86_64_GOTLoad;
- else
- Type = RIT_X86_64_GOT;
- } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
- Type = RIT_X86_64_TLV;
- } else if (Modifier != MCSymbolRefExpr::VK_None) {
- report_fatal_error("unsupported symbol modifier in relocation");
- } else {
- Type = RIT_X86_64_Signed;
-
- // The Darwin x86_64 relocation format has a problem where it cannot
- // encode an address (L<foo> + <constant>) which is outside the atom
- // containing L<foo>. Generally, this shouldn't occur but it does
- // happen when we have a RIPrel instruction with data following the
- // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
- // adjustment Darwin x86_64 uses, the offset is still negative and
- // the linker has no way to recognize this.
- //
- // To work around this, Darwin uses several special relocation types
- // to indicate the offsets. However, the specification or
- // implementation of these seems to also be incomplete; they should
- // adjust the addend as well based on the actual encoded instruction
- // (the additional bias), but instead appear to just look at the
- // final offset.
- switch (-(Target.getConstant() + (1LL << Log2Size))) {
- case 1: Type = RIT_X86_64_Signed1; break;
- case 2: Type = RIT_X86_64_Signed2; break;
- case 4: Type = RIT_X86_64_Signed4; break;
- }
- }
- } else {
- if (Modifier != MCSymbolRefExpr::VK_None)
- report_fatal_error("unsupported symbol modifier in branch "
- "relocation");
-
- Type = RIT_X86_64_Branch;
- }
- } else {
- if (Modifier == MCSymbolRefExpr::VK_GOT) {
- Type = RIT_X86_64_GOT;
- } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
- // GOTPCREL is allowed as a modifier on non-PCrel instructions, in
- // which case all we do is set the PCrel bit in the relocation entry;
- // this is used with exception handling, for example. The source is
- // required to include any necessary offset directly.
- Type = RIT_X86_64_GOT;
- IsPCRel = 1;
- } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
- report_fatal_error("TLVP symbol modifier should have been rip-rel");
- } else if (Modifier != MCSymbolRefExpr::VK_None)
- report_fatal_error("unsupported symbol modifier in relocation");
- else
- Type = RIT_X86_64_Unsigned;
- }