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[AsmPrinter][TLOF] 32-bit MachO support for replacing GOT equivalents 

Add MachO 32-bit (i.e. arm and x86) support for replacing global GOT equivalent
symbol accesses. Unlike 64-bit targets, there's no GOTPCREL relocation, and
access through a non_lazy_symbol_pointers section is used instead.

-- before

    _extgotequiv:
       .long _extfoo

    _delta:
       .long _extgotequiv-_delta

-- after

    _delta:
       .long L_extfoo$non_lazy_ptr-_delta

       .section __IMPORT,__pointers,non_lazy_symbol_pointers
    L_extfoo$non_lazy_ptr:
       .indirect_symbol _extfoo
       .long 0

llvm-svn: 231475
This commit is contained in:
Bruno Cardoso Lopes 2015-03-06 13:49:05 +00:00
parent 52b1391df6
commit 618c67a018
9 changed files with 177 additions and 22 deletions
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7
llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
View File

@ -88,6 +88,7 @@ public:
class TargetLoweringObjectFileMachO : public TargetLoweringObjectFile {
public:
virtual ~TargetLoweringObjectFileMachO() {}
TargetLoweringObjectFileMachO();
/// Extract the dependent library name from a linker option string. Returns
/// StringRef() if the option does not specify a library.
@ -122,6 +123,12 @@ public:
MCSymbol *getCFIPersonalitySymbol(const GlobalValue *GV, Mangler &Mang,
const TargetMachine &TM,
MachineModuleInfo *MMI) const override;
/// Get MachO PC relative GOT entry relocation
const MCExpr *getIndirectSymViaGOTPCRel(const MCSymbol *Sym,
const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI,
MCStreamer &Streamer) const override;
};

5
llvm/include/llvm/Target/TargetLoweringObjectFile.h
View File

@ -29,19 +29,20 @@ namespace llvm {
class MCSymbol;
class MCSymbolRefExpr;
class MCStreamer;
class MCValue;
class ConstantExpr;
class GlobalValue;
class TargetMachine;
class TargetLoweringObjectFile : public MCObjectFileInfo {
MCContext *Ctx;
const DataLayout *DL;
TargetLoweringObjectFile(
const TargetLoweringObjectFile&) = delete;
void operator=(const TargetLoweringObjectFile&) = delete;
protected:
const DataLayout *DL;
bool SupportIndirectSymViaGOTPCRel;
bool SupportGOTPCRelWithOffset;
@ -178,7 +179,9 @@ public:
/// \brief Get the target specific PC relative GOT entry relocation
virtual const MCExpr *getIndirectSymViaGOTPCRel(const MCSymbol *Sym,
const MCValue &MV,
int64_t Offset,
MachineModuleInfo *MMI,
MCStreamer &Streamer) const {
return nullptr;
}

9
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
View File

@ -2084,7 +2084,9 @@ static void handleIndirectSymViaGOTPCRel(AsmPrinter &AP, const MCExpr **ME,
//
// gotpcrelcst := <offset from @foo base> + <cst>
//
// Only encode <cst> if the target supports it.
// If gotpcrelcst is positive it means that we can safely fold the pc rel
// displacement into the GOTPCREL. We can also can have an extra offset <cst>
// if the target knows how to encode it.
//
int64_t GOTPCRelCst = Offset + MV.getConstant();
if (GOTPCRelCst < 0)
@ -2113,9 +2115,8 @@ static void handleIndirectSymViaGOTPCRel(AsmPrinter &AP, const MCExpr **ME,
unsigned NumUses = Result.second;
const GlobalValue *FinalGV = dyn_cast<GlobalValue>(GV->getOperand(0));
const MCSymbol *FinalSym = AP.getSymbol(FinalGV);
*ME = AP.getObjFileLowering().getIndirectSymViaGOTPCRel(FinalSym,
GOTPCRelCst,
AP.OutStreamer);
*ME = AP.getObjFileLowering().getIndirectSymViaGOTPCRel(
FinalSym, MV, Offset, AP.MMI, AP.OutStreamer);
// Update GOT equivalent usage information
--NumUses;

66
llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View File

@ -31,6 +31,7 @@
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
@ -431,6 +432,11 @@ TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
// MachO
//===----------------------------------------------------------------------===//
TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
: TargetLoweringObjectFile() {
SupportIndirectSymViaGOTPCRel = true;
}
/// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
/// option string. Returns StringRef() if the option does not specify a library.
StringRef TargetLoweringObjectFileMachO::
@ -705,6 +711,66 @@ MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
return SSym;
}
const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
// Although MachO 32-bit targets do not explictly have a GOTPCREL relocation
// as 64-bit do, we replace the GOT equivalent by accessing the final symbol
// through a non_lazy_ptr stub instead. One advantage is that it allows the
// computation of deltas to final external symbols. Example:
//
// _extgotequiv:
// .long _extfoo
//
// _delta:
// .long _extgotequiv-_delta
//
// is transformed to:
//
// _delta:
// .long L_extfoo$non_lazy_ptr-(_delta+0)
//
// .section __IMPORT,__pointers,non_lazy_symbol_pointers
// L_extfoo$non_lazy_ptr:
// .indirect_symbol _extfoo
// .long 0
//
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCContext &Ctx = getContext();
// The offset must consider the original displacement from the base symbol
// since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
Offset = -MV.getConstant();
const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
// Access the final symbol via sym$non_lazy_ptr and generate the appropriated
// non_lazy_ptr stubs.
SmallString<128> Name;
StringRef Suffix = "$non_lazy_ptr";
Name += DL->getPrivateGlobalPrefix();
Name += Sym->getName();
Name += Suffix;
MCSymbol *Stub = Ctx.GetOrCreateSymbol(Name);
MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
if (!StubSym.getPointer())
StubSym = MachineModuleInfoImpl::
StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
const MCExpr *BSymExpr =
MCSymbolRefExpr::Create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
const MCExpr *LHS =
MCSymbolRefExpr::Create(Stub, MCSymbolRefExpr::VK_None, Ctx);
if (!Offset)
return MCBinaryExpr::CreateSub(LHS, BSymExpr, Ctx);
const MCExpr *RHS =
MCBinaryExpr::CreateAdd(BSymExpr, MCConstantExpr::Create(Offset, Ctx), Ctx);
return MCBinaryExpr::CreateSub(LHS, RHS, Ctx);
}
//===----------------------------------------------------------------------===//
// COFF
//===----------------------------------------------------------------------===//

7
llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
View File

@ -13,6 +13,7 @@
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Dwarf.h"
using namespace llvm;
using namespace dwarf;
@ -25,7 +26,6 @@ void AArch64_ELFTargetObjectFile::Initialize(MCContext &Ctx,
AArch64_MachoTargetObjectFile::AArch64_MachoTargetObjectFile()
: TargetLoweringObjectFileMachO() {
SupportIndirectSymViaGOTPCRel = true;
SupportGOTPCRelWithOffset = false;
}
@ -58,7 +58,10 @@ MCSymbol *AArch64_MachoTargetObjectFile::getCFIPersonalitySymbol(
}
const MCExpr *AArch64_MachoTargetObjectFile::getIndirectSymViaGOTPCRel(
const MCSymbol *Sym, int64_t Offset, MCStreamer &Streamer) const {
const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
assert((Offset+MV.getConstant() == 0) &&
"Arch64 does not support GOT PC rel with extra offset");
// On ARM64 Darwin, we can reference symbols with foo@GOT-., which
// is an indirect pc-relative reference.
const MCExpr *Res =

7
llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
View File

@ -36,9 +36,10 @@ public:
const TargetMachine &TM,
MachineModuleInfo *MMI) const override;
const MCExpr *
getIndirectSymViaGOTPCRel(const MCSymbol *Sym, int64_t Offset,
MCStreamer &Streamer) const override;
const MCExpr *getIndirectSymViaGOTPCRel(const MCSymbol *Sym,
const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI,
MCStreamer &Streamer) const override;
};
} // end namespace llvm

12
llvm/lib/Target/X86/X86TargetObjectFile.cpp
View File

@ -15,17 +15,13 @@
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Target/TargetLowering.h"
using namespace llvm;
using namespace dwarf;
X86_64MachoTargetObjectFile::X86_64MachoTargetObjectFile()
: TargetLoweringObjectFileMachO() {
SupportIndirectSymViaGOTPCRel = true;
}
const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
const TargetMachine &TM, MachineModuleInfo *MMI,
@ -52,13 +48,15 @@ MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol(
}
const MCExpr *X86_64MachoTargetObjectFile::getIndirectSymViaGOTPCRel(
const MCSymbol *Sym, int64_t Offset, MCStreamer &Streamer) const {
const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
// On Darwin/X86-64, we need to use foo@GOTPCREL+4 to access the got entry
// from a data section. In case there's an additional offset, then use
// foo@GOTPCREL+4+<offset>.
unsigned FinalOff = Offset+MV.getConstant()+4;
const MCExpr *Res =
MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext());
const MCExpr *Off = MCConstantExpr::Create(Offset+4, getContext());
const MCExpr *Off = MCConstantExpr::Create(FinalOff, getContext());
return MCBinaryExpr::CreateAdd(Res, Off, getContext());
}

9
llvm/lib/Target/X86/X86TargetObjectFile.h
View File

@ -19,8 +19,6 @@ namespace llvm {
/// x86-64.
class X86_64MachoTargetObjectFile : public TargetLoweringObjectFileMachO {
public:
X86_64MachoTargetObjectFile();
const MCExpr *
getTTypeGlobalReference(const GlobalValue *GV, unsigned Encoding,
Mangler &Mang, const TargetMachine &TM,
@ -33,9 +31,10 @@ namespace llvm {
const TargetMachine &TM,
MachineModuleInfo *MMI) const override;
const MCExpr *
getIndirectSymViaGOTPCRel(const MCSymbol *Sym, int64_t Offset,
MCStreamer &Streamer) const override;
const MCExpr *getIndirectSymViaGOTPCRel(const MCSymbol *Sym,
const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI,
MCStreamer &Streamer) const override;
};
/// \brief This implemenatation is used for X86 ELF targets that don't

77
llvm/test/MC/MachO/cstexpr-gotpcrel-32.ll Normal file
View File

@ -0,0 +1,77 @@
; RUN: llc -mtriple=i386-apple-darwin %s -o %t
; RUN: FileCheck %s < %t
; RUN: FileCheck %s -check-prefix=GOT-EQUIV < %t
; RUN: llc -mtriple=arm-apple-darwin %s -o %t
; RUN: FileCheck %s < %t
; RUN: FileCheck %s -check-prefix=GOT-EQUIV < %t
; GOT equivalent globals references can be replaced by the GOT entry of the
; final symbol instead.
%struct.data = type { i32, %struct.anon }
%struct.anon = type { i32, i32 }
; Check that these got equivalent symbols are never emitted or used
; GOT-EQUIV-NOT: _localgotequiv
; GOT-EQUIV-NOT: _extgotequiv
@localfoo = global i32 42
@localgotequiv = private unnamed_addr constant i32* @localfoo
@extfoo = external global i32
@extgotequiv = private unnamed_addr constant i32* @extfoo
; Don't replace GOT equivalent usage within instructions and emit the GOT
; equivalent since it can't be replaced by the GOT entry. @bargotequiv is
; used by an instruction inside @t0.
;
; CHECK: l_bargotequiv:
; CHECK-NEXT: .long _extbar
@extbar = external global i32
@bargotequiv = private unnamed_addr constant i32* @extbar
@table = global [4 x %struct.data] [
; CHECK-LABEL: _table
%struct.data { i32 1, %struct.anon { i32 2, i32 3 } },
; Test GOT equivalent usage inside nested constant arrays.
; CHECK: .long 5
; CHECK-NOT: l_localgotequiv-(_table+20)
; CHECK-NEXT: L_localfoo$non_lazy_ptr-(_table+20)
%struct.data { i32 4, %struct.anon { i32 5,
i32 sub (i32 ptrtoint (i32** @localgotequiv to i32),
i32 ptrtoint (i32* getelementptr inbounds ([4 x %struct.data]* @table, i32 0, i32 1, i32 1, i32 1) to i32))}
},
; CHECK: .long 5
; CHECK-NOT: l_extgotequiv-(_table+32)
; CHECK-NEXT: L_extfoo$non_lazy_ptr-(_table+32)
%struct.data { i32 4, %struct.anon { i32 5,
i32 sub (i32 ptrtoint (i32** @extgotequiv to i32),
i32 ptrtoint (i32* getelementptr inbounds ([4 x %struct.data]* @table, i32 0, i32 2, i32 1, i32 1) to i32))}
},
; Test support for arbitrary constants into the GOTPCREL offset
; CHECK: .long 5
; CHECK-NOT: (l_extgotequiv-(_table+44))+24
; CHECK-NEXT: L_extfoo$non_lazy_ptr-(_table+20)
%struct.data { i32 4, %struct.anon { i32 5,
i32 add (i32 sub (i32 ptrtoint (i32** @extgotequiv to i32),
i32 ptrtoint (i32* getelementptr inbounds ([4 x %struct.data]* @table, i32 0, i32 3, i32 1, i32 1) to i32)),
i32 24)}
}
], align 16
; Test multiple uses of GOT equivalents.
; CHECK-LABEL: _delta
; CHECK: .long L_extfoo$non_lazy_ptr-_delta
@delta = global i32 sub (i32 ptrtoint (i32** @extgotequiv to i32),
i32 ptrtoint (i32* @delta to i32))
; CHECK-LABEL: _deltaplus:
; CHECK: .long L_localfoo$non_lazy_ptr-(_deltaplus-55)
@deltaplus = global i32 add (i32 sub (i32 ptrtoint (i32** @localgotequiv to i32),
i32 ptrtoint (i32* @deltaplus to i32)),
i32 55)
define i32 @t0(i32 %a) {
%x = add i32 sub (i32 ptrtoint (i32** @bargotequiv to i32),
i32 ptrtoint (i32 (i32)* @t0 to i32)), %a
ret i32 %x
}