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d6675baf7a
With the "wasm32-unknown-unknown-wasm" triple, this allows writing out simple wasm object files, and is another step in a larger series toward migrating from ELF to general wasm object support. Note that this code and the binary format itself is still experimental. llvm-svn: 296190
93 lines
3.4 KiB
C++
93 lines
3.4 KiB
C++
//===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm Writer ---------===//
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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 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/WebAssemblyMCTargetDesc.h"
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#include "MCTargetDesc/WebAssemblyFixupKinds.h"
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#include "llvm/MC/MCFixup.h"
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#include "llvm/MC/MCSymbolWasm.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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#include "llvm/Support/Wasm.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(MCContext &Ctx, const MCValue &Target,
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const MCFixup &Fixup, bool IsPCRel) 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 (const MCSymbolRefExpr *SyExp =
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dyn_cast<MCSymbolRefExpr>(Expr))
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return cast<MCSymbolWasm>(SyExp->getSymbol()).isFunction();
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if (const MCBinaryExpr *BinOp =
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dyn_cast<MCBinaryExpr>(Expr))
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return IsFunctionExpr(BinOp->getLHS()) != IsFunctionExpr(BinOp->getRHS());
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if (const MCUnaryExpr *UnOp =
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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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unsigned WebAssemblyWasmObjectWriter::getRelocType(MCContext &Ctx,
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const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) 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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assert(!IsPCRel);
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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_GLOBAL_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 (IsFunction)
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return wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB;
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return wasm::R_WEBASSEMBLY_GLOBAL_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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return wasm::R_WEBASSEMBLY_GLOBAL_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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MCObjectWriter *llvm::createWebAssemblyWasmObjectWriter(raw_pwrite_stream &OS,
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bool Is64Bit) {
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MCWasmObjectTargetWriter *MOTW = new WebAssemblyWasmObjectWriter(Is64Bit);
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return createWasmObjectWriter(MOTW, OS);
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}
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