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ELF Code Emitter now uses CurBufferPtr, BufferBegin and BufferEnd, as do JIT and
MachO Writer. This will change with the arrival of ObjectCodeEmitter and BinaryObject git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72906 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -7,17 +7,17 @@
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "elfce"
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#include "ELFCodeEmitter.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/CodeGen/MachineConstantPool.h"
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#include "llvm/CodeGen/MachineJumpTableInfo.h"
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#include "llvm/Target/TargetAsmInfo.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Mangler.h"
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#include "llvm/Support/OutputBuffer.h"
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#include "llvm/Support/Debug.h"
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//===----------------------------------------------------------------------===//
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// ELFCodeEmitter Implementation
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@ -27,39 +27,54 @@ namespace llvm {
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/// startFunction - This callback is invoked when a new machine function is
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/// about to be emitted.
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void ELFCodeEmitter::startFunction(MachineFunction &F) {
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// Align the output buffer to the appropriate alignment.
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unsigned Align = 16; // FIXME: GENERICIZE!!
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void ELFCodeEmitter::startFunction(MachineFunction &MF) {
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const TargetData *TD = TM.getTargetData();
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const Function *F = MF.getFunction();
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// Align the output buffer to the appropriate alignment, power of 2.
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unsigned FnAlign = F->getAlignment();
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unsigned TDAlign = TD->getPrefTypeAlignment(F->getType());
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unsigned Align = std::max(FnAlign, TDAlign);
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assert(!(Align & (Align-1)) && "Alignment is not a power of two!");
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// Get the ELF Section that this function belongs in.
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ES = &EW.getSection(".text", ELFWriter::ELFSection::SHT_PROGBITS,
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ELFWriter::ELFSection::SHF_EXECINSTR |
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ELFWriter::ELFSection::SHF_ALLOC);
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OutBuffer = &ES->SectionData;
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cerr << "FIXME: This code needs to be updated for changes in the "
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<< "CodeEmitter interfaces. In particular, this should set "
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<< "BufferBegin/BufferEnd/CurBufferPtr, not deal with OutBuffer!";
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abort();
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ES = &EW.getTextSection();
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// FIXME: better memory management, this will be replaced by BinaryObjects
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ES->SectionData.reserve(4096);
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BufferBegin = &ES->SectionData[0];
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BufferEnd = BufferBegin + ES->SectionData.capacity();
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// Upgrade the section alignment if required.
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if (ES->Align < Align) ES->Align = Align;
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// Add padding zeros to the end of the buffer to make sure that the
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// function will start on the correct byte alignment within the section.
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OutputBuffer OB(*OutBuffer,
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TM.getTargetData()->getPointerSizeInBits() == 64,
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TM.getTargetData()->isLittleEndian());
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OB.align(Align);
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FnStart = OutBuffer->size();
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// Round the size up to the correct alignment for starting the new function.
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ES->Size = (ES->Size + (Align-1)) & (-Align);
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// Snaity check on allocated space for text section
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assert( ES->Size < 4096 && "no more space in TextSection" );
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// FIXME: Using ES->Size directly here instead of calculating it from the
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// output buffer size (impossible because the code emitter deals only in raw
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// bytes) forces us to manually synchronize size and write padding zero bytes
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// to the output buffer for all non-text sections. For text sections, we do
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// not synchonize the output buffer, and we just blow up if anyone tries to
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// write non-code to it. An assert should probably be added to
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// AddSymbolToSection to prevent calling it on the text section.
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CurBufferPtr = BufferBegin + ES->Size;
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// Record function start address relative to BufferBegin
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FnStartPtr = CurBufferPtr;
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}
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/// finishFunction - This callback is invoked after the function is completely
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/// finished.
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bool ELFCodeEmitter::finishFunction(MachineFunction &F) {
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// We now know the size of the function, add a symbol to represent it.
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ELFWriter::ELFSym FnSym(F.getFunction());
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bool ELFCodeEmitter::finishFunction(MachineFunction &MF) {
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// Add a symbol to represent the function.
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ELFWriter::ELFSym FnSym(MF.getFunction());
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// Figure out the binding (linkage) of the symbol.
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switch (F.getFunction()->getLinkage()) {
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switch (MF.getFunction()->getLinkage()) {
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default:
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// appending linkage is illegal for functions.
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assert(0 && "Unknown linkage type!");
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@ -79,15 +94,20 @@ bool ELFCodeEmitter::finishFunction(MachineFunction &F) {
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break;
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}
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ES->Size = OutBuffer->size();
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// Set the symbol type as a function
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FnSym.SetType(ELFWriter::ELFSym::STT_FUNC);
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FnSym.SectionIdx = ES->SectionIdx;
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FnSym.Value = FnStart; // Value = Offset from start of Section.
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FnSym.Size = OutBuffer->size()-FnStart;
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FnSym.Size = CurBufferPtr-FnStartPtr;
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// Offset from start of Section
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FnSym.Value = FnStartPtr-BufferBegin;
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// Finally, add it to the symtab.
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EW.SymbolTable.push_back(FnSym);
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// Update Section Size
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ES->Size = CurBufferPtr - BufferBegin;
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return false;
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}
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@ -22,10 +22,9 @@ namespace llvm {
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ELFWriter &EW;
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TargetMachine &TM;
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ELFWriter::ELFSection *ES; // Section to write to.
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std::vector<unsigned char> *OutBuffer;
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size_t FnStart;
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uint8_t *FnStartPtr;
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public:
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explicit ELFCodeEmitter(ELFWriter &ew) : EW(ew), TM(EW.TM), OutBuffer(0) {}
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explicit ELFCodeEmitter(ELFWriter &ew) : EW(ew), TM(EW.TM) {}
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void startFunction(MachineFunction &F);
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bool finishFunction(MachineFunction &F);
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@ -168,6 +168,12 @@ namespace llvm {
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return *SN;
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}
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ELFSection &getTextSection() {
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return getSection(".text", ELFWriter::ELFSection::SHT_PROGBITS,
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ELFWriter::ELFSection::SHF_EXECINSTR |
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ELFWriter::ELFSection::SHF_ALLOC);
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}
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ELFSection &getDataSection() {
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return getSection(".data", ELFSection::SHT_PROGBITS,
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ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC);
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