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6c4b40def77622a5cf62a219ef4af63dc876e144
clang-p2996/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
Stefan Pintilie 6c4b40def7 [PowerPC][Future] Add Support For Functions That Do Not Use A TOC. 
On PowerPC most functions require a valid TOC pointer.

This is the case because either the function itself needs to use this
pointer to access the TOC or because other functions that are called
from that function expect a valid TOC pointer in the register R2.
The main exception to this is leaf functions that do not access the TOC
since they are guaranteed not to need a valid TOC pointer.

This patch introduces a feature that will allow more functions to not
require a valid TOC pointer in R2.

Differential Revision: https://reviews.llvm.org/D73664
2020-04-08 08:07:35 -05:00

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//===-- PPCELFObjectWriter.cpp - PPC ELF Writer ---------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/PPCFixupKinds.h"
#include "MCTargetDesc/PPCMCExpr.h"
#include "MCTargetDesc/PPCMCTargetDesc.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
namespace {
class PPCELFObjectWriter : public MCELFObjectTargetWriter {
public:
PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI);
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
bool needsRelocateWithSymbol(const MCSymbol &Sym,
unsigned Type) const override;
};
}
PPCELFObjectWriter::PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI)
: MCELFObjectTargetWriter(Is64Bit, OSABI,
Is64Bit ? ELF::EM_PPC64 : ELF::EM_PPC,
/*HasRelocationAddend*/ true) {}
static MCSymbolRefExpr::VariantKind getAccessVariant(const MCValue &Target,
const MCFixup &Fixup) {
const MCExpr *Expr = Fixup.getValue();
if (Expr->getKind() != MCExpr::Target)
return Target.getAccessVariant();
switch (cast<PPCMCExpr>(Expr)->getKind()) {
case PPCMCExpr::VK_PPC_None:
return MCSymbolRefExpr::VK_None;
case PPCMCExpr::VK_PPC_LO:
return MCSymbolRefExpr::VK_PPC_LO;
case PPCMCExpr::VK_PPC_HI:
return MCSymbolRefExpr::VK_PPC_HI;
case PPCMCExpr::VK_PPC_HA:
return MCSymbolRefExpr::VK_PPC_HA;
case PPCMCExpr::VK_PPC_HIGH:
return MCSymbolRefExpr::VK_PPC_HIGH;
case PPCMCExpr::VK_PPC_HIGHA:
return MCSymbolRefExpr::VK_PPC_HIGHA;
case PPCMCExpr::VK_PPC_HIGHERA:
return MCSymbolRefExpr::VK_PPC_HIGHERA;
case PPCMCExpr::VK_PPC_HIGHER:
return MCSymbolRefExpr::VK_PPC_HIGHER;
case PPCMCExpr::VK_PPC_HIGHEST:
return MCSymbolRefExpr::VK_PPC_HIGHEST;
case PPCMCExpr::VK_PPC_HIGHESTA:
return MCSymbolRefExpr::VK_PPC_HIGHESTA;
}
llvm_unreachable("unknown PPCMCExpr kind");
}
unsigned PPCELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
MCFixupKind Kind = Fixup.getKind();
if (Kind >= FirstLiteralRelocationKind)
return Kind - FirstLiteralRelocationKind;
MCSymbolRefExpr::VariantKind Modifier = getAccessVariant(Target, Fixup);
// determine the type of the relocation
unsigned Type;
if (IsPCRel) {
switch (Fixup.getTargetKind()) {
default:
llvm_unreachable("Unimplemented");
case PPC::fixup_ppc_br24:
case PPC::fixup_ppc_br24abs:
case PPC::fixup_ppc_br24_notoc:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC_REL24;
break;
case MCSymbolRefExpr::VK_PLT:
Type = ELF::R_PPC_PLTREL24;
break;
case MCSymbolRefExpr::VK_PPC_LOCAL:
Type = ELF::R_PPC_LOCAL24PC;
break;
case MCSymbolRefExpr::VK_PPC_NOTOC:
Type = ELF::R_PPC64_REL24_NOTOC;
break;
}
break;
case PPC::fixup_ppc_brcond14:
case PPC::fixup_ppc_brcond14abs:
Type = ELF::R_PPC_REL14;
break;
case PPC::fixup_ppc_half16:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC_REL16;
break;
case MCSymbolRefExpr::VK_PPC_LO:
Type = ELF::R_PPC_REL16_LO;
break;
case MCSymbolRefExpr::VK_PPC_HI:
Type = ELF::R_PPC_REL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_HA:
Type = ELF::R_PPC_REL16_HA;
break;
}
break;
case PPC::fixup_ppc_half16ds:
Target.print(errs());
errs() << '\n';
report_fatal_error("Invalid PC-relative half16ds relocation");
case FK_Data_4:
case FK_PCRel_4:
Type = ELF::R_PPC_REL32;
break;
case FK_Data_8:
case FK_PCRel_8:
Type = ELF::R_PPC64_REL64;
break;
}
} else {
switch (Fixup.getTargetKind()) {
default: llvm_unreachable("invalid fixup kind!");
case PPC::fixup_ppc_br24abs:
Type = ELF::R_PPC_ADDR24;
break;
case PPC::fixup_ppc_brcond14abs:
Type = ELF::R_PPC_ADDR14; // XXX: or BRNTAKEN?_
break;
case PPC::fixup_ppc_half16:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC_ADDR16;
break;
case MCSymbolRefExpr::VK_PPC_LO:
Type = ELF::R_PPC_ADDR16_LO;
break;
case MCSymbolRefExpr::VK_PPC_HI:
Type = ELF::R_PPC_ADDR16_HI;
break;
case MCSymbolRefExpr::VK_PPC_HA:
Type = ELF::R_PPC_ADDR16_HA;
break;
case MCSymbolRefExpr::VK_PPC_HIGH:
Type = ELF::R_PPC64_ADDR16_HIGH;
break;
case MCSymbolRefExpr::VK_PPC_HIGHA:
Type = ELF::R_PPC64_ADDR16_HIGHA;
break;
case MCSymbolRefExpr::VK_PPC_HIGHER:
Type = ELF::R_PPC64_ADDR16_HIGHER;
break;
case MCSymbolRefExpr::VK_PPC_HIGHERA:
Type = ELF::R_PPC64_ADDR16_HIGHERA;
break;
case MCSymbolRefExpr::VK_PPC_HIGHEST:
Type = ELF::R_PPC64_ADDR16_HIGHEST;
break;
case MCSymbolRefExpr::VK_PPC_HIGHESTA:
Type = ELF::R_PPC64_ADDR16_HIGHESTA;
break;
case MCSymbolRefExpr::VK_GOT:
Type = ELF::R_PPC_GOT16;
break;
case MCSymbolRefExpr::VK_PPC_GOT_LO:
Type = ELF::R_PPC_GOT16_LO;
break;
case MCSymbolRefExpr::VK_PPC_GOT_HI:
Type = ELF::R_PPC_GOT16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_HA:
Type = ELF::R_PPC_GOT16_HA;
break;
case MCSymbolRefExpr::VK_PPC_TOC:
Type = ELF::R_PPC64_TOC16;
break;
case MCSymbolRefExpr::VK_PPC_TOC_LO:
Type = ELF::R_PPC64_TOC16_LO;
break;
case MCSymbolRefExpr::VK_PPC_TOC_HI:
Type = ELF::R_PPC64_TOC16_HI;
break;
case MCSymbolRefExpr::VK_PPC_TOC_HA:
Type = ELF::R_PPC64_TOC16_HA;
break;
case MCSymbolRefExpr::VK_TPREL:
Type = ELF::R_PPC_TPREL16;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_LO:
Type = ELF::R_PPC_TPREL16_LO;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HI:
Type = ELF::R_PPC_TPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HA:
Type = ELF::R_PPC_TPREL16_HA;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
Type = ELF::R_PPC64_TPREL16_HIGH;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
Type = ELF::R_PPC64_TPREL16_HIGHA;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
Type = ELF::R_PPC64_TPREL16_HIGHER;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
Type = ELF::R_PPC64_TPREL16_HIGHERA;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
Type = ELF::R_PPC64_TPREL16_HIGHEST;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
Type = ELF::R_PPC64_TPREL16_HIGHESTA;
break;
case MCSymbolRefExpr::VK_DTPREL:
Type = ELF::R_PPC64_DTPREL16;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
Type = ELF::R_PPC64_DTPREL16_LO;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
Type = ELF::R_PPC64_DTPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
Type = ELF::R_PPC64_DTPREL16_HA;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
Type = ELF::R_PPC64_DTPREL16_HIGH;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
Type = ELF::R_PPC64_DTPREL16_HIGHA;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
Type = ELF::R_PPC64_DTPREL16_HIGHER;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
Type = ELF::R_PPC64_DTPREL16_HIGHERA;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
Type = ELF::R_PPC64_DTPREL16_HIGHEST;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
Type = ELF::R_PPC64_DTPREL16_HIGHESTA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
if (is64Bit())
Type = ELF::R_PPC64_GOT_TLSGD16;
else
Type = ELF::R_PPC_GOT_TLSGD16;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
Type = ELF::R_PPC64_GOT_TLSGD16_LO;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
Type = ELF::R_PPC64_GOT_TLSGD16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
Type = ELF::R_PPC64_GOT_TLSGD16_HA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
if (is64Bit())
Type = ELF::R_PPC64_GOT_TLSLD16;
else
Type = ELF::R_PPC_GOT_TLSLD16;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
Type = ELF::R_PPC64_GOT_TLSLD16_LO;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
Type = ELF::R_PPC64_GOT_TLSLD16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
Type = ELF::R_PPC64_GOT_TLSLD16_HA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
/* We don't have R_PPC64_GOT_TPREL16, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_TPREL16_DS. */
Type = ELF::R_PPC64_GOT_TPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
/* We don't have R_PPC64_GOT_TPREL16_LO, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_TPREL16_LO_DS. */
Type = ELF::R_PPC64_GOT_TPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
Type = ELF::R_PPC64_GOT_TPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
/* We don't have R_PPC64_GOT_DTPREL16, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_DTPREL16_DS. */
Type = ELF::R_PPC64_GOT_DTPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
/* We don't have R_PPC64_GOT_DTPREL16_LO, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_DTPREL16_LO_DS. */
Type = ELF::R_PPC64_GOT_DTPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
Type = ELF::R_PPC64_GOT_TPREL16_HA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
Type = ELF::R_PPC64_GOT_DTPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
Type = ELF::R_PPC64_GOT_DTPREL16_HA;
break;
}
break;
case PPC::fixup_ppc_half16ds:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC64_ADDR16_DS;
break;
case MCSymbolRefExpr::VK_PPC_LO:
Type = ELF::R_PPC64_ADDR16_LO_DS;
break;
case MCSymbolRefExpr::VK_GOT:
Type = ELF::R_PPC64_GOT16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_LO:
Type = ELF::R_PPC64_GOT16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_TOC:
Type = ELF::R_PPC64_TOC16_DS;
break;
case MCSymbolRefExpr::VK_PPC_TOC_LO:
Type = ELF::R_PPC64_TOC16_LO_DS;
break;
case MCSymbolRefExpr::VK_TPREL:
Type = ELF::R_PPC64_TPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_LO:
Type = ELF::R_PPC64_TPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_DTPREL:
Type = ELF::R_PPC64_DTPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
Type = ELF::R_PPC64_DTPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
Type = ELF::R_PPC64_GOT_TPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
Type = ELF::R_PPC64_GOT_TPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
Type = ELF::R_PPC64_GOT_DTPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
Type = ELF::R_PPC64_GOT_DTPREL16_LO_DS;
break;
}
break;
case PPC::fixup_ppc_nofixup:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_PPC_TLSGD:
if (is64Bit())
Type = ELF::R_PPC64_TLSGD;
else
Type = ELF::R_PPC_TLSGD;
break;
case MCSymbolRefExpr::VK_PPC_TLSLD:
if (is64Bit())
Type = ELF::R_PPC64_TLSLD;
else
Type = ELF::R_PPC_TLSLD;
break;
case MCSymbolRefExpr::VK_PPC_TLS:
if (is64Bit())
Type = ELF::R_PPC64_TLS;
else
Type = ELF::R_PPC_TLS;
break;
}
break;
case FK_Data_8:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_PPC_TOCBASE:
Type = ELF::R_PPC64_TOC;
break;
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC64_ADDR64;
break;
case MCSymbolRefExpr::VK_PPC_DTPMOD:
Type = ELF::R_PPC64_DTPMOD64;
break;
case MCSymbolRefExpr::VK_TPREL:
Type = ELF::R_PPC64_TPREL64;
break;
case MCSymbolRefExpr::VK_DTPREL:
Type = ELF::R_PPC64_DTPREL64;
break;
}
break;
case FK_Data_4:
Type = ELF::R_PPC_ADDR32;
break;
case FK_Data_2:
Type = ELF::R_PPC_ADDR16;
break;
}
}
return Type;
}
bool PPCELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
unsigned Type) const {
switch (Type) {
default:
return false;
case ELF::R_PPC_REL24:
case ELF::R_PPC64_REL24_NOTOC:
// If the target symbol has a local entry point, we must keep the
// target symbol to preserve that information for the linker.
// The "other" values are stored in the last 6 bits of the second byte.
// The traditional defines for STO values assume the full byte and thus
// the shift to pack it.
unsigned Other = cast<MCSymbolELF>(Sym).getOther() << 2;
return (Other & ELF::STO_PPC64_LOCAL_MASK) != 0;
}
}
std::unique_ptr<MCObjectTargetWriter>
llvm::createPPCELFObjectWriter(bool Is64Bit, uint8_t OSABI) {
return std::make_unique<PPCELFObjectWriter>(Is64Bit, OSABI);
}
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