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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
135 lines
4.6 KiB
C++
135 lines
4.6 KiB
C++
//===-- WebAssemblyAsmBackend.cpp - WebAssembly Assembler Backend ---------===//
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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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/// \file
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/// This file implements the WebAssemblyAsmBackend class.
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///
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/WebAssemblyFixupKinds.h"
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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/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/MC/MCWasmObjectWriter.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(support::little), Is64Bit(Is64Bit) {}
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~WebAssemblyAsmBackend() override {}
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unsigned getNumFixupKinds() const override {
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return WebAssembly::NumTargetFixupKinds;
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}
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const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
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void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
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const MCValue &Target, MutableArrayRef<char> Data,
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uint64_t Value, bool IsPCRel,
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const MCSubtargetInfo *STI) const override;
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std::unique_ptr<MCObjectTargetWriter>
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createObjectTargetWriter() 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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bool mayNeedRelaxation(const MCInst &Inst,
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const MCSubtargetInfo &STI) const override {
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return false;
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}
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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(raw_ostream &OS, uint64_t Count) const override;
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};
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const MCFixupKindInfo &
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WebAssemblyAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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const static MCFixupKindInfo Infos[WebAssembly::NumTargetFixupKinds] = {
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// This table *must* be in the order that the fixup_* kinds are defined in
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// WebAssemblyFixupKinds.h.
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//
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// Name Offset (bits) Size (bits) Flags
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{"fixup_code_sleb128_i32", 0, 5 * 8, 0},
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{"fixup_code_sleb128_i64", 0, 10 * 8, 0},
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{"fixup_code_uleb128_i32", 0, 5 * 8, 0},
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};
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if (Kind < FirstTargetFixupKind)
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return MCAsmBackend::getFixupKindInfo(Kind);
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assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
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"Invalid kind!");
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return Infos[Kind - FirstTargetFixupKind];
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}
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bool WebAssemblyAsmBackend::writeNopData(raw_ostream &OS,
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uint64_t Count) const {
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for (uint64_t i = 0; i < Count; ++i)
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OS << char(WebAssembly::Nop);
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return true;
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}
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void WebAssemblyAsmBackend::applyFixup(const MCAssembler &Asm,
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const MCFixup &Fixup,
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const MCValue &Target,
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MutableArrayRef<char> Data,
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uint64_t Value, bool IsPCRel,
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const MCSubtargetInfo *STI) 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 = alignTo(Info.TargetSize, 8) / 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 <= Data.size() && "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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std::unique_ptr<MCObjectTargetWriter>
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WebAssemblyAsmBackend::createObjectTargetWriter() const {
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return createWebAssemblyWasmObjectWriter(Is64Bit);
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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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