132 lines
4.6 KiB
C++
132 lines
4.6 KiB
C++
//===-- WebAssemblyUtilities.cpp - WebAssembly Utility Functions ----------===//
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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 implements several utility functions for WebAssembly.
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///
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//===----------------------------------------------------------------------===//
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#include "WebAssemblyUtilities.h"
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#include "WebAssemblyMachineFunctionInfo.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/MC/MCContext.h"
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using namespace llvm;
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const char *const WebAssembly::ClangCallTerminateFn = "__clang_call_terminate";
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const char *const WebAssembly::CxaBeginCatchFn = "__cxa_begin_catch";
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const char *const WebAssembly::CxaRethrowFn = "__cxa_rethrow";
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const char *const WebAssembly::StdTerminateFn = "_ZSt9terminatev";
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const char *const WebAssembly::PersonalityWrapperFn =
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"_Unwind_Wasm_CallPersonality";
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/// Test whether MI is a child of some other node in an expression tree.
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bool WebAssembly::isChild(const MachineInstr &MI,
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const WebAssemblyFunctionInfo &MFI) {
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if (MI.getNumOperands() == 0)
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return false;
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const MachineOperand &MO = MI.getOperand(0);
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if (!MO.isReg() || MO.isImplicit() || !MO.isDef())
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return false;
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Register Reg = MO.getReg();
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return Register::isVirtualRegister(Reg) && MFI.isVRegStackified(Reg);
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}
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bool WebAssembly::mayThrow(const MachineInstr &MI) {
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switch (MI.getOpcode()) {
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case WebAssembly::THROW:
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case WebAssembly::THROW_S:
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case WebAssembly::RETHROW:
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case WebAssembly::RETHROW_S:
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return true;
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}
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if (isCallIndirect(MI.getOpcode()))
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return true;
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if (!MI.isCall())
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return false;
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const MachineOperand &MO = getCalleeOp(MI);
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assert(MO.isGlobal() || MO.isSymbol());
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if (MO.isSymbol()) {
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// Some intrinsics are lowered to calls to external symbols, which are then
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// lowered to calls to library functions. Most of libcalls don't throw, but
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// we only list some of them here now.
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// TODO Consider adding 'nounwind' info in TargetLowering::CallLoweringInfo
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// instead for more accurate info.
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const char *Name = MO.getSymbolName();
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if (strcmp(Name, "memcpy") == 0 || strcmp(Name, "memmove") == 0 ||
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strcmp(Name, "memset") == 0)
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return false;
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return true;
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}
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const auto *F = dyn_cast<Function>(MO.getGlobal());
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if (!F)
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return true;
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if (F->doesNotThrow())
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return false;
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// These functions never throw
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if (F->getName() == CxaBeginCatchFn || F->getName() == PersonalityWrapperFn ||
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F->getName() == ClangCallTerminateFn || F->getName() == StdTerminateFn)
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return false;
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// TODO Can we exclude call instructions that are marked as 'nounwind' in the
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// original LLVm IR? (Even when the callee may throw)
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return true;
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}
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const MachineOperand &WebAssembly::getCalleeOp(const MachineInstr &MI) {
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switch (MI.getOpcode()) {
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case WebAssembly::CALL:
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case WebAssembly::CALL_S:
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case WebAssembly::RET_CALL:
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case WebAssembly::RET_CALL_S:
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return MI.getOperand(MI.getNumExplicitDefs());
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case WebAssembly::CALL_INDIRECT:
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case WebAssembly::CALL_INDIRECT_S:
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case WebAssembly::RET_CALL_INDIRECT:
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case WebAssembly::RET_CALL_INDIRECT_S:
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return MI.getOperand(MI.getNumOperands() - 1);
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default:
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llvm_unreachable("Not a call instruction");
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}
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}
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MCSymbolWasm *
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WebAssembly::getOrCreateFunctionTableSymbol(MCContext &Ctx,
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const StringRef &Name) {
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// FIXME: Duplicates functionality from
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// MC/WasmObjectWriter::recordRelocation.
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MCSymbolWasm *Sym = cast_or_null<MCSymbolWasm>(Ctx.lookupSymbol(Name));
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if (Sym) {
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if (!Sym->isFunctionTable())
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Ctx.reportError(SMLoc(), "symbol is not a wasm funcref table");
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} else {
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Sym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(Name));
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Sym->setFunctionTable();
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// The default function table is synthesized by the linker.
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Sym->setUndefined();
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}
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return Sym;
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}
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// Find a catch instruction from an EH pad.
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MachineInstr *WebAssembly::findCatch(MachineBasicBlock *EHPad) {
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assert(EHPad->isEHPad());
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auto Pos = EHPad->begin();
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// Skip any label or debug instructions. Also skip 'end' marker instructions
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// that may exist after marker placement in CFGStackify.
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while (Pos != EHPad->end() &&
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(Pos->isLabel() || Pos->isDebugInstr() || isMarker(Pos->getOpcode())))
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Pos++;
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if (Pos != EHPad->end() && WebAssembly::isCatch(Pos->getOpcode()))
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return &*Pos;
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return nullptr;
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}
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