llvm/lib/CodeGen/ELFCodeEmitter.cpp
Bruno Cardoso Lopes c997d45ae5 Support for ELF Visibility
Emission for globals, using the correct data sections
Function alignment can be computed for each target using TargetELFWriterInfo
Some small fixes



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73201 91177308-0d34-0410-b5e6-96231b3b80d8
2009-06-11 19:16:03 +00:00

132 lines
4.5 KiB
C++

//===-- 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/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) {
// Get the ELF Section that this function belongs in.
ES = &EW.getTextSection();
DOUT << "processing function: " << MF.getFunction()->getName() << "\n";
// FIXME: better memory management, this will be replaced by BinaryObjects
ES->SectionData.reserve(4096);
BufferBegin = &ES->SectionData[0];
BufferEnd = BufferBegin + ES->SectionData.capacity();
// Align the output buffer with function alignment, and
// upgrade the section alignment if required
unsigned Align =
TM.getELFWriterInfo()->getFunctionAlignment(MF.getFunction());
if (ES->Align < Align) ES->Align = Align;
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