c56f1d34bc
Given a thread-local symbol x with global-dynamic access, the generated
code to obtain x's address is:
Instruction Relocation Symbol
addis ra,r2,x@got@tlsgd@ha R_PPC64_GOT_TLSGD16_HA x
addi r3,ra,x@got@tlsgd@l R_PPC64_GOT_TLSGD16_L x
bl __tls_get_addr(x@tlsgd) R_PPC64_TLSGD x
R_PPC64_REL24 __tls_get_addr
nop
<use address in r3>
The implementation borrows from the medium code model work for introducing
special forms of ADDIS and ADDI into the DAG representation. This is made
slightly more complicated by having to introduce a call to the external
function __tls_get_addr. Using the full call machinery is overkill and,
more importantly, makes it difficult to add a special relocation. So I've
introduced another opcode GET_TLS_ADDR to represent the function call, and
surrounded it with register copies to set up the parameter and return value.
Most of the code is pretty straightforward. I ran into one peculiarity
when I introduced a new PPC opcode BL8_NOP_ELF_TLSGD, which is just like
BL8_NOP_ELF except that it takes another parameter to represent the symbol
("x" above) that requires a relocation on the call. Something in the
TblGen machinery causes BL8_NOP_ELF and BL8_NOP_ELF_TLSGD to be treated
identically during the emit phase, so this second operand was never
visited to generate relocations. This is the reason for the slightly
messy workaround in PPCMCCodeEmitter.cpp:getDirectBrEncoding().
Two new tests are included to demonstrate correct external assembly and
correct generation of relocations using the integrated assembler.
Comments welcome!
Thanks,
Bill
llvm-svn: 169910
209 lines
6.8 KiB
C++
209 lines
6.8 KiB
C++
//===-- PPCELFObjectWriter.cpp - PPC ELF Writer ---------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/PPCMCTargetDesc.h"
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#include "MCTargetDesc/PPCFixupKinds.h"
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/ErrorHandling.h"
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using namespace llvm;
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namespace {
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class PPCELFObjectWriter : public MCELFObjectTargetWriter {
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public:
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PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI);
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virtual ~PPCELFObjectWriter();
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protected:
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virtual unsigned getRelocTypeInner(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const;
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virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
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bool IsPCRel, bool IsRelocWithSymbol,
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int64_t Addend) const;
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virtual const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const;
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virtual void adjustFixupOffset(const MCFixup &Fixup, uint64_t &RelocOffset);
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};
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}
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PPCELFObjectWriter::PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI)
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: MCELFObjectTargetWriter(Is64Bit, OSABI,
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Is64Bit ? ELF::EM_PPC64 : ELF::EM_PPC,
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/*HasRelocationAddend*/ true) {}
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PPCELFObjectWriter::~PPCELFObjectWriter() {
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}
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unsigned PPCELFObjectWriter::getRelocTypeInner(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const
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{
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MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
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MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
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// determine the type of the relocation
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unsigned Type;
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if (IsPCRel) {
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switch ((unsigned)Fixup.getKind()) {
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default:
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llvm_unreachable("Unimplemented");
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case PPC::fixup_ppc_br24:
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Type = ELF::R_PPC_REL24;
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break;
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case FK_PCRel_4:
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Type = ELF::R_PPC_REL32;
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break;
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}
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} else {
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switch ((unsigned)Fixup.getKind()) {
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default: llvm_unreachable("invalid fixup kind!");
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case PPC::fixup_ppc_br24:
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Type = ELF::R_PPC_ADDR24;
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break;
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case PPC::fixup_ppc_brcond14:
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Type = ELF::R_PPC_ADDR14; // XXX: or BRNTAKEN?_
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break;
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case PPC::fixup_ppc_ha16:
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switch (Modifier) {
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default: llvm_unreachable("Unsupported Modifier");
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case MCSymbolRefExpr::VK_PPC_TPREL16_HA:
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Type = ELF::R_PPC_TPREL16_HA;
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break;
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case MCSymbolRefExpr::VK_None:
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Type = ELF::R_PPC_ADDR16_HA;
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break;
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case MCSymbolRefExpr::VK_PPC_TOC16_HA:
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Type = ELF::R_PPC64_TOC16_HA;
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break;
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case MCSymbolRefExpr::VK_PPC_GOT_TLSGD16_HA:
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Type = ELF::R_PPC64_GOT_TLSGD16_HA;
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break;
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}
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break;
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case PPC::fixup_ppc_lo16:
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switch (Modifier) {
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default: llvm_unreachable("Unsupported Modifier");
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case MCSymbolRefExpr::VK_PPC_TPREL16_LO:
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Type = ELF::R_PPC_TPREL16_LO;
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break;
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case MCSymbolRefExpr::VK_None:
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Type = ELF::R_PPC_ADDR16_LO;
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break;
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case MCSymbolRefExpr::VK_PPC_TOC16_LO:
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Type = ELF::R_PPC64_TOC16_LO;
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break;
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case MCSymbolRefExpr::VK_PPC_GOT_TLSGD16_LO:
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Type = ELF::R_PPC64_GOT_TLSGD16_LO;
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break;
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}
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break;
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case PPC::fixup_ppc_lo14:
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Type = ELF::R_PPC_ADDR14;
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break;
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case PPC::fixup_ppc_toc:
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Type = ELF::R_PPC64_TOC;
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break;
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case PPC::fixup_ppc_toc16:
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Type = ELF::R_PPC64_TOC16;
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break;
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case PPC::fixup_ppc_toc16_ds:
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switch (Modifier) {
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default: llvm_unreachable("Unsupported Modifier");
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case MCSymbolRefExpr::VK_PPC_TOC_ENTRY:
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Type = ELF::R_PPC64_TOC16_DS;
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break;
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case MCSymbolRefExpr::VK_PPC_TOC16_LO:
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Type = ELF::R_PPC64_TOC16_LO_DS;
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break;
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case MCSymbolRefExpr::VK_PPC_GOT_TPREL16_DS:
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Type = ELF::R_PPC64_GOT_TPREL16_DS;
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break;
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}
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break;
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case PPC::fixup_ppc_tlsreg:
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Type = ELF::R_PPC64_TLS;
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break;
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case PPC::fixup_ppc_tlsgd:
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Type = ELF::R_PPC64_TLSGD;
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break;
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case FK_Data_8:
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switch (Modifier) {
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default: llvm_unreachable("Unsupported Modifier");
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case MCSymbolRefExpr::VK_PPC_TOC:
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Type = ELF::R_PPC64_TOC;
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break;
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case MCSymbolRefExpr::VK_None:
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Type = ELF::R_PPC64_ADDR64;
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break;
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}
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break;
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case FK_Data_4:
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Type = ELF::R_PPC_ADDR32;
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break;
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case FK_Data_2:
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Type = ELF::R_PPC_ADDR16;
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break;
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}
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}
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return Type;
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}
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unsigned PPCELFObjectWriter::GetRelocType(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel,
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bool IsRelocWithSymbol,
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int64_t Addend) const {
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return getRelocTypeInner(Target, Fixup, IsPCRel);
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}
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const MCSymbol *PPCELFObjectWriter::undefinedExplicitRelSym(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const {
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assert(Target.getSymA() && "SymA cannot be 0");
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const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol();
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unsigned RelocType = getRelocTypeInner(Target, Fixup, IsPCRel);
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// The .odp creation emits a relocation against the symbol ".TOC." which
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// create a R_PPC64_TOC relocation. However the relocation symbol name
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// in final object creation should be NULL, since the symbol does not
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// really exist, it is just the reference to TOC base for the current
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// object file.
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bool EmitThisSym = RelocType != ELF::R_PPC64_TOC;
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if (EmitThisSym && !Symbol.isTemporary())
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return &Symbol;
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return NULL;
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}
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void PPCELFObjectWriter::
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adjustFixupOffset(const MCFixup &Fixup, uint64_t &RelocOffset) {
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switch ((unsigned)Fixup.getKind()) {
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case PPC::fixup_ppc_ha16:
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case PPC::fixup_ppc_lo16:
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case PPC::fixup_ppc_toc16:
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case PPC::fixup_ppc_toc16_ds:
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RelocOffset += 2;
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break;
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default:
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break;
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}
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}
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MCObjectWriter *llvm::createPPCELFObjectWriter(raw_ostream &OS,
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bool Is64Bit,
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uint8_t OSABI) {
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MCELFObjectTargetWriter *MOTW = new PPCELFObjectWriter(Is64Bit, OSABI);
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return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
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}
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