From 40ca1f1c2e0adb6e0a7e71ebf90643768dbadfc4 Mon Sep 17 00:00:00 2001 From: Bruno Cardoso Lopes Date: Tue, 21 Jul 2009 23:13:26 +0000 Subject: [PATCH] Change ELFCodeEmitter logic to emit the constant pool and jump tables to their appropriate sections before the code itself. They need to be emitted before the function because on some targets (x86 but not x86_64) the later may reference a JT or CP entry address llvm-svn: 76672 --- llvm/include/llvm/Target/TargetELFWriterInfo.h | 2 +- llvm/lib/CodeGen/ELFCodeEmitter.cpp | 46 ++++++++++++++------------ llvm/lib/CodeGen/ELFCodeEmitter.h | 10 +++--- 3 files changed, 30 insertions(+), 28 deletions(-) diff --git a/llvm/include/llvm/Target/TargetELFWriterInfo.h b/llvm/include/llvm/Target/TargetELFWriterInfo.h index ef3ca1c..37e903c 100644 --- a/llvm/include/llvm/Target/TargetELFWriterInfo.h +++ b/llvm/include/llvm/Target/TargetELFWriterInfo.h @@ -120,7 +120,7 @@ namespace llvm { virtual unsigned getAbsoluteLabelMachineRelTy() const = 0; /// computeRelocation - Some relocatable fields could be relocated - /// directly, avoiding the emission of a relocation symbol, compute the + /// directly, avoiding the relocation symbol emission, compute the /// final relocation value for this symbol. virtual long int computeRelocation(unsigned SymOffset, unsigned RelOffset, unsigned RelTy) const = 0; diff --git a/llvm/lib/CodeGen/ELFCodeEmitter.cpp b/llvm/lib/CodeGen/ELFCodeEmitter.cpp index c77334a..fb439c6 100644 --- a/llvm/lib/CodeGen/ELFCodeEmitter.cpp +++ b/llvm/lib/CodeGen/ELFCodeEmitter.cpp @@ -54,6 +54,12 @@ void ELFCodeEmitter::startFunction(MachineFunction &MF) { // Record the function start offset FnStartOff = ES->getCurrentPCOffset(); + + // Emit constant pool and jump tables to their appropriate sections. + // They need to be emitted before the function because in some targets + // the later may reference JT or CP entry address. + emitConstantPool(MF.getConstantPool()); + emitJumpTables(MF.getJumpTableInfo()); } /// finishFunction - This callback is invoked after the function is completely @@ -78,11 +84,17 @@ bool ELFCodeEmitter::finishFunction(MachineFunction &MF) { if (!F->hasPrivateLinkage()) EW.SymbolList.push_back(FnSym); - // Emit constant pool to appropriate section(s) - emitConstantPool(MF.getConstantPool()); - - // Emit jump tables to appropriate section - emitJumpTables(MF.getJumpTableInfo()); + // Patch up Jump Table Section relocations to use the real MBBs offsets + // now that the MBB label offsets inside the function are known. + ELFSection &JTSection = EW.getJumpTableSection(); + for (std::vector::iterator MRI = JTRelocations.begin(), + MRE = JTRelocations.end(); MRI != MRE; ++MRI) { + MachineRelocation &MR = *MRI; + unsigned MBBOffset = getMachineBasicBlockAddress(MR.getBasicBlock()); + MR.setResultPointer((void*)MBBOffset); + MR.setConstantVal(ES->SectionIdx); + JTSection.addRelocation(MR); + } // Relocations // ----------- @@ -105,7 +117,7 @@ bool ELFCodeEmitter::finishFunction(MachineFunction &MF) { MR.setResultPointer((void*)Addr); } else if (MR.isJumpTableIndex()) { Addr = getJumpTableEntryAddress(MR.getJumpTableIndex()); - MR.setConstantVal(JumpTableSectionIdx); + MR.setConstantVal(JTSection.SectionIdx); MR.setResultPointer((void*)Addr); } else { llvm_unreachable("Unhandled relocation type"); @@ -114,6 +126,7 @@ bool ELFCodeEmitter::finishFunction(MachineFunction &MF) { } // Clear per-function data structures. + JTRelocations.clear(); Relocations.clear(); CPLocations.clear(); CPSections.clear(); @@ -159,21 +172,15 @@ void ELFCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) { "PIC codegen not yet handled for elf jump tables!"); const TargetELFWriterInfo *TEW = TM.getELFWriterInfo(); + unsigned EntrySize = MJTI->getEntrySize(); // Get the ELF Section to emit the jump table ELFSection &JTSection = EW.getJumpTableSection(); - JumpTableSectionIdx = JTSection.SectionIdx; - - // Entries in the JT Section are relocated against the text section - ELFSection &TextSection = EW.getTextSection(); // For each JT, record its offset from the start of the section for (unsigned i = 0, e = JT.size(); i != e; ++i) { const std::vector &MBBs = JT[i].MBBs; - DOUT << "JTSection.size(): " << JTSection.size() << "\n"; - DOUT << "JTLocations.size: " << JTLocations.size() << "\n"; - // Record JT 'i' offset in the JT section JTLocations.push_back(JTSection.size()); @@ -182,19 +189,14 @@ void ELFCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) { for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) { unsigned MachineRelTy = TEW->getAbsoluteLabelMachineRelTy(); MachineRelocation MR = - MachineRelocation::getBB(JTSection.size(), - MachineRelTy, - MBBs[mi]); - - // Offset of JT 'i' in JT section - MR.setResultPointer((void*)getMachineBasicBlockAddress(MBBs[mi])); - MR.setConstantVal(TextSection.SectionIdx); + MachineRelocation::getBB(JTSection.size(), MachineRelTy, MBBs[mi]); // Add the relocation to the Jump Table section - JTSection.addRelocation(MR); + JTRelocations.push_back(MR); // Output placeholder for MBB in the JT section - JTSection.emitWord(0); + for (unsigned s=0; s < EntrySize; ++s) + JTSection.emitByte(0); } } } diff --git a/llvm/lib/CodeGen/ELFCodeEmitter.h b/llvm/lib/CodeGen/ELFCodeEmitter.h index d7f178d..b5e9c84 100644 --- a/llvm/lib/CodeGen/ELFCodeEmitter.h +++ b/llvm/lib/CodeGen/ELFCodeEmitter.h @@ -31,14 +31,14 @@ namespace llvm { /// Relocations - Record relocations needed by the current function std::vector Relocations; + /// JTRelocations - Record relocations needed by the relocation + /// section. + std::vector JTRelocations; + /// FnStartPtr - Function offset from the beginning of ELFSection 'ES' uintptr_t FnStartOff; - - /// JumpTableSectionIdx - Holds the index of the Jump Table Section - unsigned JumpTableSectionIdx; public: - explicit ELFCodeEmitter(ELFWriter &ew) : EW(ew), TM(EW.TM), - JumpTableSectionIdx(0) {} + explicit ELFCodeEmitter(ELFWriter &ew) : EW(ew), TM(EW.TM) {} /// addRelocation - Register new relocations for this function void addRelocation(const MachineRelocation &MR) { -- 2.7.4