forked from OSchip/llvm-project
77 lines
2.5 KiB
C++
77 lines
2.5 KiB
C++
//===- AVR.cpp ------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// AVR is a Harvard-architecture 8-bit micrcontroller designed for small
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// baremetal programs. All AVR-family processors have 32 8-bit registers.
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// The tiniest AVR has 32 byte RAM and 1 KiB program memory, and the largest
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// one supports up to 2^24 data address space and 2^22 code address space.
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//
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// Since it is a baremetal programming, there's usually no loader to load
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// ELF files on AVRs. You are expected to link your program against address
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// 0 and pull out a .text section from the result using objcopy, so that you
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// can write the linked code to on-chip flush memory. You can do that with
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// the following commands:
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//
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// ld.lld -Ttext=0 -o foo foo.o
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// objcopy -O binary --only-section=.text foo output.bin
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//
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// Note that the current AVR support is very preliminary so you can't
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// link any useful program yet, though.
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//
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//===----------------------------------------------------------------------===//
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#include "InputFiles.h"
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#include "Symbols.h"
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#include "Target.h"
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#include "lld/Common/ErrorHandler.h"
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#include "llvm/Object/ELF.h"
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#include "llvm/Support/Endian.h"
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using namespace llvm;
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using namespace llvm::object;
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using namespace llvm::support::endian;
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using namespace llvm::ELF;
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using namespace lld;
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using namespace lld::elf;
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namespace {
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class AVR final : public TargetInfo {
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public:
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AVR();
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RelExpr getRelExpr(RelType type, const Symbol &s,
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const uint8_t *loc) const override;
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void relocateOne(uint8_t *loc, RelType type, uint64_t val) const override;
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};
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} // namespace
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AVR::AVR() { noneRel = R_AVR_NONE; }
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RelExpr AVR::getRelExpr(RelType type, const Symbol &s,
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const uint8_t *loc) const {
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return R_ABS;
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}
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void AVR::relocateOne(uint8_t *loc, RelType type, uint64_t val) const {
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switch (type) {
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case R_AVR_CALL: {
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uint16_t hi = val >> 17;
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uint16_t lo = val >> 1;
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write16le(loc, read16le(loc) | ((hi >> 1) << 4) | (hi & 1));
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write16le(loc + 2, lo);
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break;
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}
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default:
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error(getErrorLocation(loc) + "unrecognized relocation " + toString(type));
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}
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}
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TargetInfo *elf::getAVRTargetInfo() {
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static AVR target;
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return ⌖
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}
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