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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
138 lines
4.8 KiB
C++
138 lines
4.8 KiB
C++
//===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm Writer ---------===//
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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 handles Wasm-specific object emission, converting LLVM's
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/// internal fixups into the appropriate relocations.
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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/BinaryFormat/Wasm.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCFixup.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/MCSectionWasm.h"
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#include "llvm/MC/MCSymbolWasm.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/MC/MCWasmObjectWriter.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/ErrorHandling.h"
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using namespace llvm;
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namespace {
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class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter {
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public:
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explicit WebAssemblyWasmObjectWriter(bool Is64Bit);
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private:
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unsigned getRelocType(const MCValue &Target,
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const MCFixup &Fixup) const override;
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};
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} // end anonymous namespace
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WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit)
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: MCWasmObjectTargetWriter(Is64Bit) {}
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// Test whether the given expression computes a function address.
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static bool IsFunctionExpr(const MCExpr *Expr) {
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if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr))
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return cast<MCSymbolWasm>(SyExp->getSymbol()).isFunction();
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if (auto BinOp = dyn_cast<MCBinaryExpr>(Expr))
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return IsFunctionExpr(BinOp->getLHS()) != IsFunctionExpr(BinOp->getRHS());
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if (auto UnOp = dyn_cast<MCUnaryExpr>(Expr))
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return IsFunctionExpr(UnOp->getSubExpr());
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return false;
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}
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static bool IsFunctionType(const MCValue &Target) {
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const MCSymbolRefExpr *RefA = Target.getSymA();
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return RefA && RefA->getKind() == MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX;
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}
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static const MCSection *GetFixupSection(const MCExpr *Expr) {
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if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr)) {
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if (SyExp->getSymbol().isInSection())
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return &SyExp->getSymbol().getSection();
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return nullptr;
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}
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if (auto BinOp = dyn_cast<MCBinaryExpr>(Expr)) {
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auto SectionLHS = GetFixupSection(BinOp->getLHS());
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auto SectionRHS = GetFixupSection(BinOp->getRHS());
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return SectionLHS == SectionRHS ? nullptr : SectionLHS;
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}
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if (auto UnOp = dyn_cast<MCUnaryExpr>(Expr))
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return GetFixupSection(UnOp->getSubExpr());
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return nullptr;
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}
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static bool IsGlobalType(const MCValue &Target) {
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const MCSymbolRefExpr *RefA = Target.getSymA();
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return RefA && RefA->getKind() == MCSymbolRefExpr::VK_WebAssembly_GLOBAL;
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}
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static bool IsEventType(const MCValue &Target) {
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const MCSymbolRefExpr *RefA = Target.getSymA();
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return RefA && RefA->getKind() == MCSymbolRefExpr::VK_WebAssembly_EVENT;
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}
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unsigned WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
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const MCFixup &Fixup) const {
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// WebAssembly functions are not allocated in the data address space. To
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// resolve a pointer to a function, we must use a special relocation type.
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bool IsFunction = IsFunctionExpr(Fixup.getValue());
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switch (unsigned(Fixup.getKind())) {
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case WebAssembly::fixup_code_sleb128_i32:
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if (IsFunction)
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return wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB;
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return wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB;
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case WebAssembly::fixup_code_sleb128_i64:
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llvm_unreachable("fixup_sleb128_i64 not implemented yet");
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case WebAssembly::fixup_code_uleb128_i32:
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if (IsGlobalType(Target))
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return wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB;
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if (IsFunctionType(Target))
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return wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB;
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if (IsFunction)
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return wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB;
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if (IsEventType(Target))
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return wasm::R_WEBASSEMBLY_EVENT_INDEX_LEB;
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return wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB;
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case FK_Data_4:
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if (IsFunction)
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return wasm::R_WEBASSEMBLY_TABLE_INDEX_I32;
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if (auto Section = static_cast<const MCSectionWasm *>(
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GetFixupSection(Fixup.getValue()))) {
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if (Section->getKind().isText())
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return wasm::R_WEBASSEMBLY_FUNCTION_OFFSET_I32;
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else if (!Section->isWasmData())
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return wasm::R_WEBASSEMBLY_SECTION_OFFSET_I32;
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}
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return wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32;
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case FK_Data_8:
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llvm_unreachable("FK_Data_8 not implemented yet");
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default:
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llvm_unreachable("unimplemented fixup kind");
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}
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}
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std::unique_ptr<MCObjectTargetWriter>
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llvm::createWebAssemblyWasmObjectWriter(bool Is64Bit) {
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return llvm::make_unique<WebAssemblyWasmObjectWriter>(Is64Bit);
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}
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