3acb187d95
This changes locals from being declared by the emitLocal hook in WebAssemblyTargetStreamer, rather than with an instruction. After exploring the infastructure in LLVM more, this seems to make more sense since declaring locals doesn't use an encoded opcode. This also adds more 0xd opcodes, type encodings, and miscellaneous binary encoding bits. llvm-svn: 285040
106 lines
3.4 KiB
C++
106 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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for (uint64_t i = 0; i < Count; ++i)
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OW->write8(WebAssembly::Nop);
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return true;
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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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