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//===-- lib/CodeGen/ELFCodeEmitter.cpp ------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "elfce"
#include "ELFCodeEmitter.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
//===----------------------------------------------------------------------===//
// ELFCodeEmitter Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// startFunction - This callback is invoked when a new machine function is
/// about to be emitted.
void ELFCodeEmitter::startFunction(MachineFunction &MF) {
const TargetData *TD = TM.getTargetData();
const Function *F = MF.getFunction();
// Align the output buffer to the appropriate alignment, power of 2.
unsigned FnAlign = F->getAlignment();
unsigned TDAlign = TD->getPrefTypeAlignment(F->getType());
unsigned Align = std::max(FnAlign, TDAlign);
assert(!(Align & (Align-1)) && "Alignment is not a power of two!");
// Get the ELF Section that this function belongs in.
ES = &EW.getTextSection();
// FIXME: better memory management, this will be replaced by BinaryObjects
ES->SectionData.reserve(4096);
BufferBegin = &ES->SectionData[0];
BufferEnd = BufferBegin + ES->SectionData.capacity();
// Upgrade the section alignment if required.
if (ES->Align < Align) ES->Align = Align;
// Round the size up to the correct alignment for starting the new function.
ES->Size = (ES->Size + (Align-1)) & (-Align);
// Snaity check on allocated space for text section
assert( ES->Size < 4096 && "no more space in TextSection" );
// FIXME: Using ES->Size directly here instead of calculating it from the
// output buffer size (impossible because the code emitter deals only in raw
// bytes) forces us to manually synchronize size and write padding zero bytes
// to the output buffer for all non-text sections. For text sections, we do
// not synchonize the output buffer, and we just blow up if anyone tries to
// write non-code to it. An assert should probably be added to
// AddSymbolToSection to prevent calling it on the text section.
CurBufferPtr = BufferBegin + ES->Size;
// Record function start address relative to BufferBegin
FnStartPtr = CurBufferPtr;
}
/// finishFunction - This callback is invoked after the function is completely
/// finished.
bool ELFCodeEmitter::finishFunction(MachineFunction &MF) {
// Add a symbol to represent the function.
ELFSym FnSym(MF.getFunction());
// Update Section Size
ES->Size = CurBufferPtr - BufferBegin;
// Figure out the binding (linkage) of the symbol.
switch (MF.getFunction()->getLinkage()) {
default:
// appending linkage is illegal for functions.
assert(0 && "Unknown linkage type!");
case GlobalValue::ExternalLinkage:
FnSym.SetBind(ELFSym::STB_GLOBAL);
break;
case GlobalValue::LinkOnceAnyLinkage:
case GlobalValue::LinkOnceODRLinkage:
case GlobalValue::WeakAnyLinkage:
case GlobalValue::WeakODRLinkage:
FnSym.SetBind(ELFSym::STB_WEAK);
break;
case GlobalValue::PrivateLinkage:
assert (0 && "PrivateLinkage should not be in the symbol table.");
case GlobalValue::InternalLinkage:
FnSym.SetBind(ELFSym::STB_LOCAL);
break;
}
// Set the symbol type as a function
FnSym.SetType(ELFSym::STT_FUNC);
FnSym.SectionIdx = ES->SectionIdx;
FnSym.Size = CurBufferPtr-FnStartPtr;
// Offset from start of Section
FnSym.Value = FnStartPtr-BufferBegin;
// Finally, add it to the symtab.
EW.SymbolTable.push_back(FnSym);
// Relocations
// -----------
// If we have emitted any relocations to function-specific objects such as
// basic blocks, constant pools entries, or jump tables, record their
// addresses now so that we can rewrite them with the correct addresses
// later.
for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
MachineRelocation &MR = Relocations[i];
intptr_t Addr;
if (MR.isBasicBlock()) {
Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
MR.setConstantVal(ES->SectionIdx);
MR.setResultPointer((void*)Addr);
} else if (MR.isGlobalValue()) {
EW.PendingGlobals.insert(MR.getGlobalValue());
} else {
assert(0 && "Unhandled relocation type");
}
ES->Relocations.push_back(MR);
}
Relocations.clear();
return false;
}
} // end namespace llvm
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