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1) Proper emit displacements for x86, using absolute relocations where necessary

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for ELF to work.  
2) RIP addressing: Use SIB bytes for absolute relocations where RegBase=0, 
IndexReg=0.
3) The JIT can get the real address of cstpools and jmptables during
code emission, fix that for object code emission

llvm-svn: 78129
This commit is contained in:
Bruno Cardoso Lopes 2009-08-05 00:11:21 +00:00
parent a8cb86c0f5
commit 21bb984953
6 changed files with 77 additions and 31 deletions
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7
include/llvm/CodeGen/JITCodeEmitter.h
View File

@ -289,6 +289,13 @@ public:
return CurBufferPtr-BufferBegin;
}
/// earlyResolveAddresses - True if the code emitter can use symbol addresses
/// during code emission time. The JIT is capable of doing this because it
/// creates jump tables or constant pools in memory on the fly while the
/// object code emitters rely on a linker to have real addresses and should
/// use relocations instead.
bool earlyResolveAddresses() const { return true; }
/// addRelocation - Whenever a relocatable address is needed, it should be
/// noted with this interface.
virtual void addRelocation(const MachineRelocation &MR) = 0;

7
include/llvm/CodeGen/MachineCodeEmitter.h
View File

@ -280,6 +280,13 @@ public:
return CurBufferPtr-BufferBegin;
}
/// earlyResolveAddresses - True if the code emitter can use symbol addresses
/// during code emission time. The JIT is capable of doing this because it
/// creates jump tables or constant pools in memory on the fly while the
/// object code emitters rely on a linker to have real addresses and should
/// use relocations instead.
virtual bool earlyResolveAddresses() const = 0;
/// addRelocation - Whenever a relocatable address is needed, it should be
/// noted with this interface.
virtual void addRelocation(const MachineRelocation &MR) = 0;

7
include/llvm/CodeGen/ObjectCodeEmitter.h
View File

@ -109,6 +109,13 @@ public:
/// noted with this interface.
void addRelocation(const MachineRelocation& relocation);
/// earlyResolveAddresses - True if the code emitter can use symbol addresses
/// during code emission time. The JIT is capable of doing this because it
/// creates jump tables or constant pools in memory on the fly while the
/// object code emitters rely on a linker to have real addresses and should
/// use relocations instead.
bool earlyResolveAddresses() const { return false; }
/// startFunction - This callback is invoked when the specified function is
/// about to be code generated. This initializes the BufferBegin/End/Ptr
/// fields.

66
lib/Target/X86/X86CodeEmitter.cpp
View File

@ -87,7 +87,7 @@ template<class CodeEmitter>
intptr_t PCAdj = 0);
void emitDisplacementField(const MachineOperand *RelocOp, int DispVal,
intptr_t PCAdj = 0);
intptr_t Adj = 0, bool IsPCRel = true);
void emitRegModRMByte(unsigned ModRMReg, unsigned RegOpcodeField);
void emitRegModRMByte(unsigned RegOpcodeField);
@ -175,7 +175,7 @@ void Emitter<CodeEmitter>::emitGlobalAddress(GlobalValue *GV, unsigned Reloc,
intptr_t PCAdj /* = 0 */,
bool NeedStub /* = false */,
bool Indirect /* = false */) {
intptr_t RelocCST = 0;
intptr_t RelocCST = Disp;
if (Reloc == X86::reloc_picrel_word)
RelocCST = PICBaseOffset;
else if (Reloc == X86::reloc_pcrel_word)
@ -309,34 +309,42 @@ static bool gvNeedsNonLazyPtr(const MachineOperand &GVOp,
template<class CodeEmitter>
void Emitter<CodeEmitter>::emitDisplacementField(const MachineOperand *RelocOp,
int DispVal, intptr_t PCAdj) {
int DispVal,
intptr_t Adj /* = 0 */,
bool IsPCRel /* = true */) {
// If this is a simple integer displacement that doesn't require a relocation,
// emit it now.
if (!RelocOp) {
emitConstant(DispVal, 4);
return;
}
// Otherwise, this is something that requires a relocation. Emit it as such
// now.
if (RelocOp->isGlobal()) {
// In 64-bit static small code model, we could potentially emit absolute.
// But it's probably not beneficial.
// But it's probably not beneficial. If the MCE supports using RIP directly
// do it, otherwise fallback to absolute (this is determined by IsPCRel).
// 89 05 00 00 00 00 mov %eax,0(%rip) # PC-relative
// 89 04 25 00 00 00 00 mov %eax,0x0 # Absolute
unsigned rt = Is64BitMode ? X86::reloc_pcrel_word
unsigned rt = Is64BitMode ?
(IsPCRel ? X86::reloc_pcrel_word : X86::reloc_absolute_word_sext)
: (IsPIC ? X86::reloc_picrel_word : X86::reloc_absolute_word);
bool NeedStub = isa<Function>(RelocOp->getGlobal());
bool Indirect = gvNeedsNonLazyPtr(*RelocOp, TM);
emitGlobalAddress(RelocOp->getGlobal(), rt, RelocOp->getOffset(),
PCAdj, NeedStub, Indirect);
Adj, NeedStub, Indirect);
} else if (RelocOp->isCPI()) {
unsigned rt = Is64BitMode ? X86::reloc_pcrel_word : X86::reloc_picrel_word;
unsigned rt = Is64BitMode ?
(IsPCRel ? X86::reloc_pcrel_word : X86::reloc_absolute_word_sext)
: (IsPCRel ? X86::reloc_picrel_word : X86::reloc_absolute_word);
emitConstPoolAddress(RelocOp->getIndex(), rt,
RelocOp->getOffset(), PCAdj);
RelocOp->getOffset(), Adj);
} else if (RelocOp->isJTI()) {
unsigned rt = Is64BitMode ? X86::reloc_pcrel_word : X86::reloc_picrel_word;
emitJumpTableAddress(RelocOp->getIndex(), rt, PCAdj);
unsigned rt = Is64BitMode ?
(IsPCRel ? X86::reloc_pcrel_word : X86::reloc_absolute_word_sext)
: (IsPCRel ? X86::reloc_picrel_word : X86::reloc_absolute_word);
emitJumpTableAddress(RelocOp->getIndex(), rt, Adj);
} else {
llvm_unreachable("Unknown value to relocate!");
}
@ -354,14 +362,14 @@ void Emitter<CodeEmitter>::emitMemModRMByte(const MachineInstr &MI,
if (Op3.isGlobal()) {
DispForReloc = &Op3;
} else if (Op3.isCPI()) {
if (Is64BitMode || IsPIC) {
if (!MCE.earlyResolveAddresses() || Is64BitMode || IsPIC) {
DispForReloc = &Op3;
} else {
DispVal += MCE.getConstantPoolEntryAddress(Op3.getIndex());
DispVal += Op3.getOffset();
}
} else if (Op3.isJTI()) {
if (Is64BitMode || IsPIC) {
if (!MCE.earlyResolveAddresses() || Is64BitMode || IsPIC) {
DispForReloc = &Op3;
} else {
DispVal += MCE.getJumpTableEntryAddress(Op3.getIndex());
@ -376,17 +384,23 @@ void Emitter<CodeEmitter>::emitMemModRMByte(const MachineInstr &MI,
unsigned BaseReg = Base.getReg();
// Indicate that the displacement will use an pcrel or absolute reference
// by default. MCEs able to resolve addresses on-the-fly use pcrel by default
// while others, unless explicit asked to use RIP, use absolute references.
bool IsPCRel = MCE.earlyResolveAddresses() ? true : false;
// Is a SIB byte needed?
// If no BaseReg, issue a RIP relative instruction only if the MCE can
// resolve addresses on-the-fly, otherwise use SIB (Intel Manual 2A, table
// 2-7) and absolute references.
if ((!Is64BitMode || DispForReloc || BaseReg != 0) &&
IndexReg.getReg() == 0 &&
(BaseReg == 0 || BaseReg == X86::RIP ||
getX86RegNum(BaseReg) != N86::ESP)) {
if (BaseReg == 0 ||
BaseReg == X86::RIP) { // Just a displacement?
IndexReg.getReg() == 0 &&
((BaseReg == 0 && MCE.earlyResolveAddresses()) || BaseReg == X86::RIP ||
(BaseReg != 0 && getX86RegNum(BaseReg) != N86::ESP))) {
if (BaseReg == 0 || BaseReg == X86::RIP) { // Just a displacement?
// Emit special case [disp32] encoding
MCE.emitByte(ModRMByte(0, RegOpcodeField, 5));
emitDisplacementField(DispForReloc, DispVal, PCAdj);
emitDisplacementField(DispForReloc, DispVal, PCAdj, true);
} else {
unsigned BaseRegNo = getX86RegNum(BaseReg);
if (!DispForReloc && DispVal == 0 && BaseRegNo != N86::EBP) {
@ -399,7 +413,7 @@ void Emitter<CodeEmitter>::emitMemModRMByte(const MachineInstr &MI,
} else {
// Emit the most general non-SIB encoding: [REG+disp32]
MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
emitDisplacementField(DispForReloc, DispVal, PCAdj);
emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
}
}
@ -435,13 +449,13 @@ void Emitter<CodeEmitter>::emitMemModRMByte(const MachineInstr &MI,
unsigned SS = SSTable[Scale.getImm()];
if (BaseReg == 0) {
// Handle the SIB byte for the case where there is no base. The
// displacement has already been output.
// Handle the SIB byte for the case where there is no base, see Intel
// Manual 2A, table 2-7. The displacement has already been output.
unsigned IndexRegNo;
if (IndexReg.getReg())
IndexRegNo = getX86RegNum(IndexReg.getReg());
else
IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
IndexRegNo = 4;
emitSIBByte(SS, IndexRegNo, 5);
} else {
unsigned BaseRegNo = getX86RegNum(BaseReg);
@ -457,7 +471,7 @@ void Emitter<CodeEmitter>::emitMemModRMByte(const MachineInstr &MI,
if (ForceDisp8) {
emitConstant(DispVal, 1);
} else if (DispVal != 0 || ForceDisp32) {
emitDisplacementField(DispForReloc, DispVal, PCAdj);
emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
}
}
}

1
lib/Target/X86/X86JITInfo.cpp
View File

@ -538,6 +538,7 @@ void X86JITInfo::relocate(void *Function, MachineRelocation *MR,
break;
}
case X86::reloc_absolute_word:
case X86::reloc_absolute_word_sext:
// Absolute relocation, just add the relocated value to the value already
// in memory.
*((unsigned*)RelocPos) += (unsigned)ResultPtr;

20
lib/Target/X86/X86Relocations.h
View File

@ -20,7 +20,9 @@ namespace llvm {
namespace X86 {
/// RelocationType - An enum for the x86 relocation codes. Note that
/// the terminology here doesn't follow x86 convention - word means
/// 32-bit and dword means 64-bit.
/// 32-bit and dword means 64-bit. The relocations will be treated
/// by JIT or ObjectCode emitters, this is transparent to the x86 code
/// emitter but JIT and ObjectCode will treat them differently
enum RelocationType {
/// reloc_pcrel_word - PC relative relocation, add the relocated value to
/// the value already in memory, after we adjust it for where the PC is.
@ -30,11 +32,19 @@ namespace llvm {
/// value to the value already in memory, after we adjust it for where the
/// PIC base is.
reloc_picrel_word = 1,
/// reloc_absolute_word, reloc_absolute_dword - Absolute relocation, just
/// add the relocated value to the value already in memory.
/// reloc_absolute_word - absolute relocation, just add the relocated
/// value to the value already in memory.
reloc_absolute_word = 2,
reloc_absolute_dword = 3
/// reloc_absolute_word_sext - absolute relocation, just add the relocated
/// value to the value already in memory. In object files, it represents a
/// value which must be sign-extended when resolving the relocation.
reloc_absolute_word_sext = 3,
/// reloc_absolute_dword - absolute relocation, just add the relocated
/// value to the value already in memory.
reloc_absolute_dword = 4
};
}
}