Imported Upstream version 5.18.0.246

Former-commit-id: 0c7ce5b1a7851e13f22acfd379b7f9fb304e4833

external/llvm/lib/Transforms/IPO/LoopExtractor.cpp

@@ -0,0 +1,312 @@
+//===- LoopExtractor.cpp - Extract each loop into a new function ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// A pass wrapper around the ExtractLoop() scalar transformation to extract each
+// top-level loop into its own new function. If the loop is the ONLY loop in a
+// given function, it is not touched. This is a pass most useful for debugging
+// via bugpoint.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/CodeExtractor.h"
+#include <fstream>
+#include <set>
+using namespace llvm;
+
+#define DEBUG_TYPE "loop-extract"
+
+STATISTIC(NumExtracted, "Number of loops extracted");
+
+namespace {
+  struct LoopExtractor : public LoopPass {
+    static char ID; // Pass identification, replacement for typeid
+    unsigned NumLoops;
+
+    explicit LoopExtractor(unsigned numLoops = ~0)
+      : LoopPass(ID), NumLoops(numLoops) {
+        initializeLoopExtractorPass(*PassRegistry::getPassRegistry());
+      }
+
+    bool runOnLoop(Loop *L, LPPassManager &) override;
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addRequiredID(BreakCriticalEdgesID);
+      AU.addRequiredID(LoopSimplifyID);
+      AU.addRequired<DominatorTreeWrapperPass>();
+      AU.addRequired<LoopInfoWrapperPass>();
+    }
+  };
+}
+
+char LoopExtractor::ID = 0;
+INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract",
+                      "Extract loops into new functions", false, false)
+INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
+INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_END(LoopExtractor, "loop-extract",
+                    "Extract loops into new functions", false, false)
+
+namespace {
+  /// SingleLoopExtractor - For bugpoint.
+  struct SingleLoopExtractor : public LoopExtractor {
+    static char ID; // Pass identification, replacement for typeid
+    SingleLoopExtractor() : LoopExtractor(1) {}
+  };
+} // End anonymous namespace
+
+char SingleLoopExtractor::ID = 0;
+INITIALIZE_PASS(SingleLoopExtractor, "loop-extract-single",
+                "Extract at most one loop into a new function", false, false)
+
+// createLoopExtractorPass - This pass extracts all natural loops from the
+// program into a function if it can.
+//
+Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); }
+
+bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) {
+  if (skipLoop(L))
+    return false;
+
+  // Only visit top-level loops.
+  if (L->getParentLoop())
+    return false;
+
+  // If LoopSimplify form is not available, stay out of trouble.
+  if (!L->isLoopSimplifyForm())
+    return false;
+
+  DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+  LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  bool Changed = false;
+
+  // If there is more than one top-level loop in this function, extract all of
+  // the loops. Otherwise there is exactly one top-level loop; in this case if
+  // this function is more than a minimal wrapper around the loop, extract
+  // the loop.
+  bool ShouldExtractLoop = false;
+
+  // Extract the loop if the entry block doesn't branch to the loop header.
+  TerminatorInst *EntryTI =
+    L->getHeader()->getParent()->getEntryBlock().getTerminator();
+  if (!isa<BranchInst>(EntryTI) ||
+      !cast<BranchInst>(EntryTI)->isUnconditional() ||
+      EntryTI->getSuccessor(0) != L->getHeader()) {
+    ShouldExtractLoop = true;
+  } else {
+    // Check to see if any exits from the loop are more than just return
+    // blocks.
+    SmallVector<BasicBlock*, 8> ExitBlocks;
+    L->getExitBlocks(ExitBlocks);
+    for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
+      if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) {
+        ShouldExtractLoop = true;
+        break;
+      }
+  }
+
+  if (ShouldExtractLoop) {
+    // We must omit EH pads. EH pads must accompany the invoke
+    // instruction. But this would result in a loop in the extracted
+    // function. An infinite cycle occurs when it tries to extract that loop as
+    // well.
+    SmallVector<BasicBlock*, 8> ExitBlocks;
+    L->getExitBlocks(ExitBlocks);
+    for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
+      if (ExitBlocks[i]->isEHPad()) {
+        ShouldExtractLoop = false;
+        break;
+      }
+  }
+
+  if (ShouldExtractLoop) {
+    if (NumLoops == 0) return Changed;
+    --NumLoops;
+    CodeExtractor Extractor(DT, *L);
+    if (Extractor.extractCodeRegion() != nullptr) {
+      Changed = true;
+      // After extraction, the loop is replaced by a function call, so
+      // we shouldn't try to run any more loop passes on it.
+      LPM.markLoopAsDeleted(*L);
+      LI.erase(L);
+    }
+    ++NumExtracted;
+  }
+
+  return Changed;
+}
+
+// createSingleLoopExtractorPass - This pass extracts one natural loop from the
+// program into a function if it can.  This is used by bugpoint.
+//
+Pass *llvm::createSingleLoopExtractorPass() {
+  return new SingleLoopExtractor();
+}
+
+
+// BlockFile - A file which contains a list of blocks that should not be
+// extracted.
+static cl::opt<std::string>
+BlockFile("extract-blocks-file", cl::value_desc("filename"),
+          cl::desc("A file containing list of basic blocks to not extract"),
+          cl::Hidden);
+
+namespace {
+  /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks
+  /// from the module into their own functions except for those specified by the
+  /// BlocksToNotExtract list.
+  class BlockExtractorPass : public ModulePass {
+    void LoadFile(const char *Filename);
+    void SplitLandingPadPreds(Function *F);
+
+    std::vector<BasicBlock*> BlocksToNotExtract;
+    std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName;
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    BlockExtractorPass() : ModulePass(ID) {
+      if (!BlockFile.empty())
+        LoadFile(BlockFile.c_str());
+    }
+
+    bool runOnModule(Module &M) override;
+  };
+}
+
+char BlockExtractorPass::ID = 0;
+INITIALIZE_PASS(BlockExtractorPass, "extract-blocks",
+                "Extract Basic Blocks From Module (for bugpoint use)",
+                false, false)
+
+// createBlockExtractorPass - This pass extracts all blocks (except those
+// specified in the argument list) from the functions in the module.
+//
+ModulePass *llvm::createBlockExtractorPass() {
+  return new BlockExtractorPass();
+}
+
+void BlockExtractorPass::LoadFile(const char *Filename) {
+  // Load the BlockFile...
+  std::ifstream In(Filename);
+  if (!In.good()) {
+    errs() << "WARNING: BlockExtractor couldn't load file '" << Filename
+           << "'!\n";
+    return;
+  }
+  while (In) {
+    std::string FunctionName, BlockName;
+    In >> FunctionName;
+    In >> BlockName;
+    if (!BlockName.empty())
+      BlocksToNotExtractByName.push_back(
+          std::make_pair(FunctionName, BlockName));
+  }
+}
+
+/// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke
+/// instruction. The critical edge breaker will refuse to break critical edges
+/// to a landing pad. So do them here. After this method runs, all landing pads
+/// should have only one predecessor.
+void BlockExtractorPass::SplitLandingPadPreds(Function *F) {
+  for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
+    InvokeInst *II = dyn_cast<InvokeInst>(I);
+    if (!II) continue;
+    BasicBlock *Parent = II->getParent();
+    BasicBlock *LPad = II->getUnwindDest();
+
+    // Look through the landing pad's predecessors. If one of them ends in an
+    // 'invoke', then we want to split the landing pad.
+    bool Split = false;
+    for (pred_iterator
+           PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) {
+      BasicBlock *BB = *PI;
+      if (BB->isLandingPad() && BB != Parent &&
+          isa<InvokeInst>(Parent->getTerminator())) {
+        Split = true;
+        break;
+      }
+    }
+
+    if (!Split) continue;
+
+    SmallVector<BasicBlock*, 2> NewBBs;
+    SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", NewBBs);
+  }
+}
+
+bool BlockExtractorPass::runOnModule(Module &M) {
+  if (skipModule(M))
+    return false;
+
+  std::set<BasicBlock*> TranslatedBlocksToNotExtract;
+  for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) {
+    BasicBlock *BB = BlocksToNotExtract[i];
+    Function *F = BB->getParent();
+
+    // Map the corresponding function in this module.
+    Function *MF = M.getFunction(F->getName());
+    assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?");
+
+    // Figure out which index the basic block is in its function.
+    Function::iterator BBI = MF->begin();
+    std::advance(BBI, std::distance(F->begin(), Function::iterator(BB)));
+    TranslatedBlocksToNotExtract.insert(&*BBI);
+  }
+
+  while (!BlocksToNotExtractByName.empty()) {
+    // There's no way to find BBs by name without looking at every BB inside
+    // every Function. Fortunately, this is always empty except when used by
+    // bugpoint in which case correctness is more important than performance.
+
+    std::string &FuncName  = BlocksToNotExtractByName.back().first;
+    std::string &BlockName = BlocksToNotExtractByName.back().second;
+
+    for (Function &F : M) {
+      if (F.getName() != FuncName) continue;
+
+      for (BasicBlock &BB : F) {
+        if (BB.getName() != BlockName) continue;
+
+        TranslatedBlocksToNotExtract.insert(&BB);
+      }
+    }
+
+    BlocksToNotExtractByName.pop_back();
+  }
+
+  // Now that we know which blocks to not extract, figure out which ones we WANT
+  // to extract.
+  std::vector<BasicBlock*> BlocksToExtract;
+  for (Function &F : M) {
+    SplitLandingPadPreds(&F);
+    for (BasicBlock &BB : F)
+      if (!TranslatedBlocksToNotExtract.count(&BB))
+        BlocksToExtract.push_back(&BB);
+  }
+
+  for (BasicBlock *BlockToExtract : BlocksToExtract) {
+    SmallVector<BasicBlock*, 2> BlocksToExtractVec;
+    BlocksToExtractVec.push_back(BlockToExtract);
+    if (const InvokeInst *II =
+            dyn_cast<InvokeInst>(BlockToExtract->getTerminator()))
+      BlocksToExtractVec.push_back(II->getUnwindDest());
+    CodeExtractor(BlocksToExtractVec).extractCodeRegion();
+  }
+
+  return !BlocksToExtract.empty();
+}