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