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//===--- WebAssemblyExceptionInfo.cpp - Exception Infomation --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file implements WebAssemblyException information analysis.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblyExceptionInfo.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssemblyUtilities.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/CodeGen/MachineDominanceFrontier.h"
#include "llvm/CodeGen/MachineDominators.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-exception-info"
char WebAssemblyExceptionInfo::ID = 0;
INITIALIZE_PASS_BEGIN(WebAssemblyExceptionInfo, DEBUG_TYPE,
"WebAssembly Exception Information", true, true)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(MachineDominanceFrontier)
INITIALIZE_PASS_END(WebAssemblyExceptionInfo, DEBUG_TYPE,
"WebAssembly Exception Information", true, true)
bool WebAssemblyExceptionInfo::runOnMachineFunction(MachineFunction &MF) {
LLVM_DEBUG(dbgs() << "********** Exception Info Calculation **********\n"
"********** Function: "
<< MF.getName() << '\n');
releaseMemory();
auto &MDT = getAnalysis<MachineDominatorTree>();
auto &MDF = getAnalysis<MachineDominanceFrontier>();
recalculate(MDT, MDF);
return false;
}
void WebAssemblyExceptionInfo::recalculate(
MachineDominatorTree &MDT, const MachineDominanceFrontier &MDF) {
// Postorder traversal of the dominator tree.
SmallVector<WebAssemblyException *, 8> Exceptions;
for (auto DomNode : post_order(&MDT)) {
MachineBasicBlock *EHPad = DomNode->getBlock();
if (!EHPad->isEHPad())
continue;
auto *WE = new WebAssemblyException(EHPad);
discoverAndMapException(WE, MDT, MDF);
Exceptions.push_back(WE);
}
// Add BBs to exceptions
for (auto DomNode : post_order(&MDT)) {
MachineBasicBlock *MBB = DomNode->getBlock();
WebAssemblyException *WE = getExceptionFor(MBB);
for (; WE; WE = WE->getParentException())
WE->addBlock(MBB);
}
// Add subexceptions to exceptions
for (auto *WE : Exceptions) {
if (WE->getParentException())
WE->getParentException()->getSubExceptions().push_back(WE);
else
addTopLevelException(WE);
}
// For convenience, Blocks and SubExceptions are inserted in postorder.
// Reverse the lists.
for (auto *WE : Exceptions) {
WE->reverseBlock();
std::reverse(WE->getSubExceptions().begin(), WE->getSubExceptions().end());
}
}
void WebAssemblyExceptionInfo::releaseMemory() {
BBMap.clear();
DeleteContainerPointers(TopLevelExceptions);
TopLevelExceptions.clear();
}
void WebAssemblyExceptionInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<MachineDominatorTree>();
AU.addRequired<MachineDominanceFrontier>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void WebAssemblyExceptionInfo::discoverAndMapException(
WebAssemblyException *WE, const MachineDominatorTree &MDT,
const MachineDominanceFrontier &MDF) {
unsigned NumBlocks = 0;
unsigned NumSubExceptions = 0;
// Map blocks that belong to a catchpad / cleanuppad
MachineBasicBlock *EHPad = WE->getEHPad();
SmallVector<MachineBasicBlock *, 8> WL;
WL.push_back(EHPad);
while (!WL.empty()) {
MachineBasicBlock *MBB = WL.pop_back_val();
// Find its outermost discovered exception. If this is a discovered block,
// check if it is already discovered to be a subexception of this exception.
WebAssemblyException *SubE = getOutermostException(MBB);
if (SubE) {
if (SubE != WE) {
// Discover a subexception of this exception.
SubE->setParentException(WE);
++NumSubExceptions;
NumBlocks += SubE->getBlocksVector().capacity();
// All blocks that belong to this subexception have been already
// discovered. Skip all of them. Add the subexception's landing pad's
// dominance frontier to the worklist.
for (auto &Frontier : MDF.find(SubE->getEHPad())->second)
if (MDT.dominates(EHPad, Frontier))
WL.push_back(Frontier);
}
continue;
}
// This is an undiscovered block. Map it to the current exception.
changeExceptionFor(MBB, WE);
++NumBlocks;
// Add successors dominated by the current BB to the worklist.
for (auto *Succ : MBB->successors())
if (MDT.dominates(EHPad, Succ))
WL.push_back(Succ);
}
WE->getSubExceptions().reserve(NumSubExceptions);
WE->reserveBlocks(NumBlocks);
}
WebAssemblyException *
WebAssemblyExceptionInfo::getOutermostException(MachineBasicBlock *MBB) const {
WebAssemblyException *WE = getExceptionFor(MBB);
if (WE) {
while (WebAssemblyException *Parent = WE->getParentException())
WE = Parent;
}
return WE;
}
void WebAssemblyException::print(raw_ostream &OS, unsigned Depth) const {
OS.indent(Depth * 2) << "Exception at depth " << getExceptionDepth()
<< " containing: ";
for (unsigned I = 0; I < getBlocks().size(); ++I) {
MachineBasicBlock *MBB = getBlocks()[I];
if (I)
OS << ", ";
OS << "%bb." << MBB->getNumber();
if (const auto *BB = MBB->getBasicBlock())
if (BB->hasName())
OS << "." << BB->getName();
if (getEHPad() == MBB)
OS << " (landing-pad)";
}
OS << "\n";
for (auto &SubE : SubExceptions)
SubE->print(OS, Depth + 2);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void WebAssemblyException::dump() const { print(dbgs()); }
#endif
raw_ostream &operator<<(raw_ostream &OS, const WebAssemblyException &WE) {
WE.print(OS);
return OS;
}
void WebAssemblyExceptionInfo::print(raw_ostream &OS, const Module *) const {
for (auto *WE : TopLevelExceptions)
WE->print(OS);
}
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