358 lines
14 KiB
C++
358 lines
14 KiB
C++
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// WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst //
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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 contains code to lower WebAssembly MachineInstrs to their
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/// corresponding MCInst records.
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///
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//===----------------------------------------------------------------------===//
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#include "WebAssemblyMCInstLower.h"
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "TargetInfo/WebAssemblyTargetInfo.h"
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#include "WebAssemblyAsmPrinter.h"
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#include "WebAssemblyMachineFunctionInfo.h"
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#include "WebAssemblyRuntimeLibcallSignatures.h"
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#include "llvm/CodeGen/AsmPrinter.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCSymbolWasm.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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// This disables the removal of registers when lowering into MC, as required
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// by some current tests.
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cl::opt<bool>
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WasmKeepRegisters("wasm-keep-registers", cl::Hidden,
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cl::desc("WebAssembly: output stack registers in"
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" instruction output for test purposes only."),
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cl::init(false));
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extern cl::opt<bool> EnableEmException;
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extern cl::opt<bool> EnableEmSjLj;
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static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI);
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MCSymbol *
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WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
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const GlobalValue *Global = MO.getGlobal();
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if (!isa<Function>(Global))
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return cast<MCSymbolWasm>(Printer.getSymbol(Global));
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const auto *FuncTy = cast<FunctionType>(Global->getValueType());
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const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
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const TargetMachine &TM = MF.getTarget();
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const Function &CurrentFunc = MF.getFunction();
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SmallVector<MVT, 1> ResultMVTs;
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SmallVector<MVT, 4> ParamMVTs;
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const auto *const F = dyn_cast<Function>(Global);
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computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs);
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auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs);
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bool InvokeDetected = false;
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auto *WasmSym = Printer.getMCSymbolForFunction(
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F, EnableEmException || EnableEmSjLj, Signature.get(), InvokeDetected);
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WasmSym->setSignature(Signature.get());
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Printer.addSignature(std::move(Signature));
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WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
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return WasmSym;
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}
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MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
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const MachineOperand &MO) const {
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const char *Name = MO.getSymbolName();
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auto *WasmSym = cast<MCSymbolWasm>(Printer.GetExternalSymbolSymbol(Name));
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const WebAssemblySubtarget &Subtarget = Printer.getSubtarget();
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// Except for certain known symbols, all symbols used by CodeGen are
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// functions. It's OK to hardcode knowledge of specific symbols here; this
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// method is precisely there for fetching the signatures of known
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// Clang-provided symbols.
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if (strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0 ||
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strcmp(Name, "__memory_base") == 0 || strcmp(Name, "__table_base") == 0 ||
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strcmp(Name, "__tls_size") == 0 || strcmp(Name, "__tls_align") == 0) {
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bool Mutable =
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strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0;
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WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
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WasmSym->setGlobalType(wasm::WasmGlobalType{
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uint8_t(Subtarget.hasAddr64() && strcmp(Name, "__table_base") != 0
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? wasm::WASM_TYPE_I64
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: wasm::WASM_TYPE_I32),
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Mutable});
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return WasmSym;
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}
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SmallVector<wasm::ValType, 4> Returns;
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SmallVector<wasm::ValType, 4> Params;
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if (strcmp(Name, "__cpp_exception") == 0) {
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WasmSym->setType(wasm::WASM_SYMBOL_TYPE_EVENT);
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// We can't confirm its signature index for now because there can be
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// imported exceptions. Set it to be 0 for now.
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WasmSym->setEventType(
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{wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION, /* SigIndex */ 0});
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// We may have multiple C++ compilation units to be linked together, each of
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// which defines the exception symbol. To resolve them, we declare them as
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// weak.
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WasmSym->setWeak(true);
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WasmSym->setExternal(true);
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// All C++ exceptions are assumed to have a single i32 (for wasm32) or i64
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// (for wasm64) param type and void return type. The reaon is, all C++
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// exception values are pointers, and to share the type section with
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// functions, exceptions are assumed to have void return type.
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Params.push_back(Subtarget.hasAddr64() ? wasm::ValType::I64
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: wasm::ValType::I32);
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} else { // Function symbols
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WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
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getLibcallSignature(Subtarget, Name, Returns, Params);
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}
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auto Signature =
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std::make_unique<wasm::WasmSignature>(std::move(Returns), std::move(Params));
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WasmSym->setSignature(Signature.get());
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Printer.addSignature(std::move(Signature));
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return WasmSym;
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}
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MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
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MCSymbol *Sym) const {
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MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
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unsigned TargetFlags = MO.getTargetFlags();
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switch (TargetFlags) {
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case WebAssemblyII::MO_NO_FLAG:
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break;
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case WebAssemblyII::MO_GOT:
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Kind = MCSymbolRefExpr::VK_GOT;
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break;
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case WebAssemblyII::MO_MEMORY_BASE_REL:
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Kind = MCSymbolRefExpr::VK_WASM_MBREL;
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break;
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case WebAssemblyII::MO_TLS_BASE_REL:
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Kind = MCSymbolRefExpr::VK_WASM_TLSREL;
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break;
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case WebAssemblyII::MO_TABLE_BASE_REL:
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Kind = MCSymbolRefExpr::VK_WASM_TBREL;
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break;
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default:
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llvm_unreachable("Unknown target flag on GV operand");
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}
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const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx);
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if (MO.getOffset() != 0) {
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const auto *WasmSym = cast<MCSymbolWasm>(Sym);
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if (TargetFlags == WebAssemblyII::MO_GOT)
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report_fatal_error("GOT symbol references do not support offsets");
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if (WasmSym->isFunction())
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report_fatal_error("Function addresses with offsets not supported");
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if (WasmSym->isGlobal())
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report_fatal_error("Global indexes with offsets not supported");
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if (WasmSym->isEvent())
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report_fatal_error("Event indexes with offsets not supported");
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Expr = MCBinaryExpr::createAdd(
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Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
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}
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return MCOperand::createExpr(Expr);
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}
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MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
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SmallVector<wasm::ValType, 1> &&Returns,
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SmallVector<wasm::ValType, 4> &&Params) const {
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auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
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std::move(Params));
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MCSymbol *Sym = Printer.createTempSymbol("typeindex");
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auto *WasmSym = cast<MCSymbolWasm>(Sym);
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WasmSym->setSignature(Signature.get());
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Printer.addSignature(std::move(Signature));
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WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
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const MCExpr *Expr =
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MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
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return MCOperand::createExpr(Expr);
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}
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// Return the WebAssembly type associated with the given register class.
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static wasm::ValType getType(const TargetRegisterClass *RC) {
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if (RC == &WebAssembly::I32RegClass)
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return wasm::ValType::I32;
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if (RC == &WebAssembly::I64RegClass)
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return wasm::ValType::I64;
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if (RC == &WebAssembly::F32RegClass)
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return wasm::ValType::F32;
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if (RC == &WebAssembly::F64RegClass)
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return wasm::ValType::F64;
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if (RC == &WebAssembly::V128RegClass)
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return wasm::ValType::V128;
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llvm_unreachable("Unexpected register class");
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}
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static void getFunctionReturns(const MachineInstr *MI,
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SmallVectorImpl<wasm::ValType> &Returns) {
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const Function &F = MI->getMF()->getFunction();
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const TargetMachine &TM = MI->getMF()->getTarget();
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Type *RetTy = F.getReturnType();
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SmallVector<MVT, 4> CallerRetTys;
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computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
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valTypesFromMVTs(CallerRetTys, Returns);
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}
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void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
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MCInst &OutMI) const {
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OutMI.setOpcode(MI->getOpcode());
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const MCInstrDesc &Desc = MI->getDesc();
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unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs();
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for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
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const MachineOperand &MO = MI->getOperand(I);
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MCOperand MCOp;
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switch (MO.getType()) {
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default:
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MI->print(errs());
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llvm_unreachable("unknown operand type");
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case MachineOperand::MO_MachineBasicBlock:
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MI->print(errs());
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llvm_unreachable("MachineBasicBlock operand should have been rewritten");
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case MachineOperand::MO_Register: {
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// Ignore all implicit register operands.
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if (MO.isImplicit())
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continue;
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const WebAssemblyFunctionInfo &MFI =
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*MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
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unsigned WAReg = MFI.getWAReg(MO.getReg());
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MCOp = MCOperand::createReg(WAReg);
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break;
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}
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case MachineOperand::MO_Immediate: {
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unsigned DescIndex = I - NumVariadicDefs;
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if (DescIndex < Desc.NumOperands) {
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const MCOperandInfo &Info = Desc.OpInfo[DescIndex];
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if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
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SmallVector<wasm::ValType, 4> Returns;
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SmallVector<wasm::ValType, 4> Params;
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const MachineRegisterInfo &MRI =
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MI->getParent()->getParent()->getRegInfo();
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for (const MachineOperand &MO : MI->defs())
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Returns.push_back(getType(MRI.getRegClass(MO.getReg())));
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for (const MachineOperand &MO : MI->explicit_uses())
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if (MO.isReg())
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Params.push_back(getType(MRI.getRegClass(MO.getReg())));
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// call_indirect instructions have a callee operand at the end which
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// doesn't count as a param.
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if (WebAssembly::isCallIndirect(MI->getOpcode()))
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Params.pop_back();
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// return_call_indirect instructions have the return type of the
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// caller
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if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
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getFunctionReturns(MI, Returns);
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MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params));
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break;
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} else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
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auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
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assert(BT != WebAssembly::BlockType::Invalid);
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if (BT == WebAssembly::BlockType::Multivalue) {
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SmallVector<wasm::ValType, 1> Returns;
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getFunctionReturns(MI, Returns);
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MCOp = lowerTypeIndexOperand(std::move(Returns),
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SmallVector<wasm::ValType, 4>());
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break;
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}
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} else if (Info.OperandType == WebAssembly::OPERAND_HEAPTYPE) {
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assert(static_cast<WebAssembly::HeapType>(MO.getImm()) !=
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WebAssembly::HeapType::Invalid);
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// With typed function references, this will need a case for type
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// index operands. Otherwise, fall through.
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}
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}
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MCOp = MCOperand::createImm(MO.getImm());
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break;
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}
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case MachineOperand::MO_FPImmediate: {
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// TODO: MC converts all floating point immediate operands to double.
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// This is fine for numeric values, but may cause NaNs to change bits.
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const ConstantFP *Imm = MO.getFPImm();
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if (Imm->getType()->isFloatTy())
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MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToFloat());
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else if (Imm->getType()->isDoubleTy())
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MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToDouble());
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else
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llvm_unreachable("unknown floating point immediate type");
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break;
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}
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case MachineOperand::MO_GlobalAddress:
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MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
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break;
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case MachineOperand::MO_ExternalSymbol:
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// The target flag indicates whether this is a symbol for a
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// variable or a function.
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assert(MO.getTargetFlags() == 0 &&
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"WebAssembly uses only symbol flags on ExternalSymbols");
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MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
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break;
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case MachineOperand::MO_MCSymbol:
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// This is currently used only for LSDA symbols (GCC_except_table),
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// because global addresses or other external symbols are handled above.
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assert(MO.getTargetFlags() == 0 &&
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"WebAssembly does not use target flags on MCSymbol");
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MCOp = lowerSymbolOperand(MO, MO.getMCSymbol());
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break;
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}
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OutMI.addOperand(MCOp);
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}
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if (!WasmKeepRegisters)
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removeRegisterOperands(MI, OutMI);
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else if (Desc.variadicOpsAreDefs())
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OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs()));
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}
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static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
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// Remove all uses of stackified registers to bring the instruction format
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// into its final stack form used thruout MC, and transition opcodes to
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// their _S variant.
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// We do this separate from the above code that still may need these
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// registers for e.g. call_indirect signatures.
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|
// See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
|
||
|
|
// details.
|
||
|
|
// TODO: the code above creates new registers which are then removed here.
|
||
|
|
// That code could be slightly simplified by not doing that, though maybe
|
||
|
|
// it is simpler conceptually to keep the code above in "register mode"
|
||
|
|
// until this transition point.
|
||
|
|
// FIXME: we are not processing inline assembly, which contains register
|
||
|
|
// operands, because it is used by later target generic code.
|
||
|
|
if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
|
||
|
|
return;
|
||
|
|
|
||
|
|
// Transform to _S instruction.
|
||
|
|
auto RegOpcode = OutMI.getOpcode();
|
||
|
|
auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode);
|
||
|
|
assert(StackOpcode != -1 && "Failed to stackify instruction");
|
||
|
|
OutMI.setOpcode(StackOpcode);
|
||
|
|
|
||
|
|
// Remove register operands.
|
||
|
|
for (auto I = OutMI.getNumOperands(); I; --I) {
|
||
|
|
auto &MO = OutMI.getOperand(I - 1);
|
||
|
|
if (MO.isReg()) {
|
||
|
|
OutMI.erase(&MO);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|