1 //===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm Writer ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// \brief This file handles Wasm-specific object emission, converting LLVM's
12 /// internal fixups into the appropriate relocations.
14 //===----------------------------------------------------------------------===//
16 #include "MCTargetDesc/WebAssemblyFixupKinds.h"
17 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
18 #include "llvm/BinaryFormat/Wasm.h"
19 #include "llvm/MC/MCAsmBackend.h"
20 #include "llvm/MC/MCFixup.h"
21 #include "llvm/MC/MCFixupKindInfo.h"
22 #include "llvm/MC/MCSymbolWasm.h"
23 #include "llvm/MC/MCWasmObjectWriter.h"
24 #include "llvm/MC/MCValue.h"
25 #include "llvm/Support/Casting.h"
26 #include "llvm/Support/ErrorHandling.h"
31 class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter {
33 explicit WebAssemblyWasmObjectWriter(bool Is64Bit);
36 unsigned getRelocType(const MCValue &Target,
37 const MCFixup &Fixup) const override;
39 } // end anonymous namespace
41 WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit)
42 : MCWasmObjectTargetWriter(Is64Bit) {}
44 // Test whether the given expression computes a function address.
45 static bool IsFunctionExpr(const MCExpr *Expr) {
46 if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr))
47 return cast<MCSymbolWasm>(SyExp->getSymbol()).isFunction();
49 if (auto BinOp = dyn_cast<MCBinaryExpr>(Expr))
50 return IsFunctionExpr(BinOp->getLHS()) != IsFunctionExpr(BinOp->getRHS());
52 if (auto UnOp = dyn_cast<MCUnaryExpr>(Expr))
53 return IsFunctionExpr(UnOp->getSubExpr());
58 static bool IsFunctionType(const MCValue &Target) {
59 const MCSymbolRefExpr *RefA = Target.getSymA();
60 return RefA && RefA->getKind() == MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX;
64 WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
65 const MCFixup &Fixup) const {
66 // WebAssembly functions are not allocated in the data address space. To
67 // resolve a pointer to a function, we must use a special relocation type.
68 bool IsFunction = IsFunctionExpr(Fixup.getValue());
70 switch (unsigned(Fixup.getKind())) {
71 case WebAssembly::fixup_code_global_index:
72 return wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB;
73 case WebAssembly::fixup_code_sleb128_i32:
75 return wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB;
76 return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB;
77 case WebAssembly::fixup_code_sleb128_i64:
78 llvm_unreachable("fixup_sleb128_i64 not implemented yet");
79 case WebAssembly::fixup_code_uleb128_i32:
80 if (IsFunctionType(Target))
81 return wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB;
83 return wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB;
84 return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB;
87 return wasm::R_WEBASSEMBLY_TABLE_INDEX_I32;
88 return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32;
90 llvm_unreachable("FK_Data_8 not implemented yet");
92 llvm_unreachable("unimplemented fixup kind");
96 MCObjectWriter *llvm::createWebAssemblyWasmObjectWriter(raw_pwrite_stream &OS,
98 MCWasmObjectTargetWriter *MOTW = new WebAssemblyWasmObjectWriter(Is64Bit);
99 return createWasmObjectWriter(MOTW, OS);