1 //===- AVR.cpp ------------------------------------------------------------===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // AVR is a Harvard-architecture 8-bit micrcontroller designed for small
11 // baremetal programs. All AVR-family processors have 32 8-bit registers.
12 // The tiniest AVR has 32 byte RAM and 1 KiB program memory, and the largest
13 // one supports up to 2^24 data address space and 2^22 code address space.
15 // Since it is a baremetal programming, there's usually no loader to load
16 // ELF files on AVRs. You are expected to link your program against address
17 // 0 and pull out a .text section from the result using objcopy, so that you
18 // can write the linked code to on-chip flush memory. You can do that with
19 // the following commands:
21 // ld.lld -Ttext=0 -o foo foo.o
22 // objcopy -O binary --only-section=.text foo output.bin
24 // Note that the current AVR support is very preliminary so you can't
25 // link any useful program yet, though.
27 //===----------------------------------------------------------------------===//
29 #include "InputFiles.h"
32 #include "lld/Common/ErrorHandler.h"
33 #include "llvm/Object/ELF.h"
34 #include "llvm/Support/Endian.h"
37 using namespace llvm::object;
38 using namespace llvm::support::endian;
39 using namespace llvm::ELF;
41 using namespace lld::elf;
44 class AVR final : public TargetInfo {
47 RelExpr getRelExpr(RelType Type, const Symbol &S,
48 const uint8_t *Loc) const override;
49 void relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const override;
53 AVR::AVR() { NoneRel = R_AVR_NONE; }
55 RelExpr AVR::getRelExpr(RelType Type, const Symbol &S,
56 const uint8_t *Loc) const {
60 void AVR::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const {
63 uint16_t Hi = Val >> 17;
64 uint16_t Lo = Val >> 1;
65 write16le(Loc, read16le(Loc) | ((Hi >> 1) << 4) | (Hi & 1));
66 write16le(Loc + 2, Lo);
70 error(getErrorLocation(Loc) + "unrecognized reloc " + toString(Type));
74 TargetInfo *elf::getAVRTargetInfo() {