forked from OSchip/llvm-project
104 lines
3.4 KiB
C++
104 lines
3.4 KiB
C++
//===-- WebAssemblyAsmBackend.cpp - WebAssembly Assembler Backend ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// \brief This file implements the WebAssemblyAsmBackend class.
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///
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCDirectives.h"
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixupKindInfo.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSubtargetInfo.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace {
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class WebAssemblyAsmBackend final : public MCAsmBackend {
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bool Is64Bit;
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public:
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explicit WebAssemblyAsmBackend(bool Is64Bit)
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: MCAsmBackend(), Is64Bit(Is64Bit) {}
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~WebAssemblyAsmBackend() override {}
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void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
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uint64_t Value, bool IsPCRel) const override;
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MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override;
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// No instruction requires relaxation
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bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
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const MCRelaxableFragment *DF,
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const MCAsmLayout &Layout) const override {
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return false;
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}
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unsigned getNumFixupKinds() const override {
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// We currently just use the generic fixups in MCFixup.h and don't have any
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// target-specific fixups.
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return 0;
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}
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bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
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void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
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MCInst &Res) const override {}
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bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
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};
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bool WebAssemblyAsmBackend::writeNopData(uint64_t Count,
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MCObjectWriter *OW) const {
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if (Count == 0)
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return true;
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// FIXME: Do something.
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return false;
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}
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void WebAssemblyAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
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unsigned DataSize, uint64_t Value,
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bool IsPCRel) const {
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const MCFixupKindInfo &Info = getFixupKindInfo(Fixup.getKind());
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assert(Info.Flags == 0 && "WebAssembly does not use MCFixupKindInfo flags");
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unsigned NumBytes = (Info.TargetSize + 7) / 8;
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if (Value == 0)
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return; // Doesn't change encoding.
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// Shift the value into position.
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Value <<= Info.TargetOffset;
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unsigned Offset = Fixup.getOffset();
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assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!");
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// For each byte of the fragment that the fixup touches, mask in the
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// bits from the fixup value.
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for (unsigned i = 0; i != NumBytes; ++i)
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Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
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}
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MCObjectWriter *
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WebAssemblyAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
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return createWebAssemblyELFObjectWriter(OS, Is64Bit, 0);
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}
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} // end anonymous namespace
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MCAsmBackend *llvm::createWebAssemblyAsmBackend(const Triple &TT) {
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return new WebAssemblyAsmBackend(TT.isArch64Bit());
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}
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