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//===- AVR.cpp ------------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// AVR is a Harvard-architecture 8-bit micrcontroller designed for small
// baremetal programs. All AVR-family processors have 32 8-bit registers.
// The tiniest AVR has 32 byte RAM and 1 KiB program memory, and the largest
// one supports up to 2^24 data address space and 2^22 code address space.
//
// Since it is a baremetal programming, there's usually no loader to load
// ELF files on AVRs. You are expected to link your program against address
// 0 and pull out a .text section from the result using objcopy, so that you
// can write the linked code to on-chip flush memory. You can do that with
// the following commands:
//
// ld.lld -Ttext=0 -o foo foo.o
// objcopy -O binary --only-section=.text foo output.bin
//
// Note that the current AVR support is very preliminary so you can't
// link any useful program yet, though.
//
//===----------------------------------------------------------------------===//
#include "InputFiles.h"
#include "Symbols.h"
#include "Target.h"
#include "lld/Common/ErrorHandler.h"
#include "llvm/Object/ELF.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
namespace {
class AVR final : public TargetInfo {
public:
RelExpr getRelExpr(RelType Type, const Symbol &S,
const uint8_t *Loc) const override;
void relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const override;
};
} // namespace
RelExpr AVR::getRelExpr(RelType Type, const Symbol &S,
const uint8_t *Loc) const {
return R_ABS;
}
void AVR::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const {
switch (Type) {
case R_AVR_CALL: {
uint16_t Hi = Val >> 17;
uint16_t Lo = Val >> 1;
write16le(Loc, read16le(Loc) | ((Hi >> 1) << 4) | (Hi & 1));
write16le(Loc + 2, Lo);
break;
}
default:
error(getErrorLocation(Loc) + "unrecognized reloc " + toString(Type));
}
}
TargetInfo *elf::getAVRTargetInfo() {
static AVR Target;
return &Target;
}
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