[PruneEH][NFC] Use CallGraphUpdater in PruneEH

[aeubanks]

Summary

In preparation for porting the pass to NPM.

[asbirlea]

lg

llvm/lib/Transforms/IPO/PruneEH.cpp

140

Add inside for, outside if/else:

if (SCCMightUnwind && SCCMightReturn)
          break;

[aeubanks]

Move break outside if/else

llvm/lib/Transforms/IPO/PruneEH.cpp

 //===- PruneEH.cpp - Pass which deletes unused exception handlers ---------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements a simple interprocedural pass which walks the
 // call-graph, turning invoke instructions into calls, iff the callee cannot
 // throw an exception, and marking functions 'nounwind' if they cannot throw.
 // It implements this as a bottom-up traversal of the call-graph.
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/CallGraphSCCPass.h"
 #include "llvm/Analysis/EHPersonalities.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/Utils/CallGraphUpdater.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include <algorithm>
+
 using namespace llvm;
 
 #define DEBUG_TYPE "prune-eh"
 
 STATISTIC(NumRemoved, "Number of invokes removed");
 STATISTIC(NumUnreach, "Number of noreturn calls optimized");
 
 namespace {
   struct PruneEH : public CallGraphSCCPass {
     static char ID; // Pass identification, replacement for typeid
     PruneEH() : CallGraphSCCPass(ID) {
       initializePruneEHPass(*PassRegistry::getPassRegistry());
     }
 
     // runOnSCC - Analyze the SCC, performing the transformation if possible.
     bool runOnSCC(CallGraphSCC &SCC) override;
-
   };
 }
-static bool SimplifyFunction(Function *F, CallGraph &CG);
-static void DeleteBasicBlock(BasicBlock *BB, CallGraph &CG);
+static bool SimplifyFunction(Function *F, CallGraphUpdater &CGU);
+static void DeleteBasicBlock(BasicBlock *BB, CallGraphUpdater &CGU);
 
 char PruneEH::ID = 0;
 INITIALIZE_PASS_BEGIN(PruneEH, "prune-eh",
                 "Remove unused exception handling info", false, false)
 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
 INITIALIZE_PASS_END(PruneEH, "prune-eh",
                 "Remove unused exception handling info", false, false)
 
 Pass *llvm::createPruneEHPass() { return new PruneEH(); }
 
-static bool runImpl(CallGraphSCC &SCC, CallGraph &CG) {
-  SmallPtrSet<CallGraphNode *, 8> SCCNodes;
+static bool runImpl(CallGraphUpdater &CGU, SetVector<Function *> &Functions) {
+#ifndef NDEBUG
+  for (auto *F : Functions)
+    assert(F && "null Function");
+#endif
   bool MadeChange = false;
 
-  // Fill SCCNodes with the elements of the SCC.  Used for quickly
-  // looking up whether a given CallGraphNode is in this SCC.
-  for (CallGraphNode *I : SCC)
-    SCCNodes.insert(I);
-
   // First pass, scan all of the functions in the SCC, simplifying them
   // according to what we know.
-  for (CallGraphNode *I : SCC)
-    if (Function *F = I->getFunction())
-      MadeChange |= SimplifyFunction(F, CG);
+  for (Function *F : Functions)
+    MadeChange |= SimplifyFunction(F, CGU);
 
   // Next, check to see if any callees might throw or if there are any external
   // functions in this SCC: if so, we cannot prune any functions in this SCC.
   // Definitions that are weak and not declared non-throwing might be
   // overridden at linktime with something that throws, so assume that.
   // If this SCC includes the unwind instruction, we KNOW it throws, so
   // obviously the SCC might throw.
   //
   bool SCCMightUnwind = false, SCCMightReturn = false;
-  for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end();
-       (!SCCMightUnwind || !SCCMightReturn) && I != E; ++I) {
-    Function *F = (*I)->getFunction();
-    if (!F) {
-      SCCMightUnwind = true;
-      SCCMightReturn = true;
-    } else if (!F->hasExactDefinition()) {
+  for (Function *F : Functions) {
+    if (!F->hasExactDefinition()) {
       SCCMightUnwind |= !F->doesNotThrow();
       SCCMightReturn |= !F->doesNotReturn();
     } else {
       bool CheckUnwind = !SCCMightUnwind && !F->doesNotThrow();
       bool CheckReturn = !SCCMightReturn && !F->doesNotReturn();
       // Determine if we should scan for InlineAsm in a naked function as it
       // is the only way to return without a ReturnInst.  Only do this for
       // no-inline functions as functions which may be inlined cannot
if (!F->hasExactDefinition()) {
             break;
 
           // Check to see if this function performs an unwind or calls an
           // unwinding function.
           if (CheckUnwind && !SCCMightUnwind && I.mayThrow()) {
             bool InstMightUnwind = true;
             if (const auto *CI = dyn_cast<CallInst>(&I)) {
               if (Function *Callee = CI->getCalledFunction()) {
-                CallGraphNode *CalleeNode = CG[Callee];
                 // If the callee is outside our current SCC then we may throw
                 // because it might.  If it is inside, do nothing.
-                if (SCCNodes.count(CalleeNode) > 0)
+                if (Functions.contains(Callee))
                   InstMightUnwind = false;
               }
             }
             SCCMightUnwind |= InstMightUnwind;
           }
           if (CheckReturnViaAsm && !SCCMightReturn)
             if (const auto *CB = dyn_cast<CallBase>(&I))
               if (const auto *IA = dyn_cast<InlineAsm>(CB->getCalledOperand()))
                 if (IA->hasSideEffects())
                   SCCMightReturn = true;
         }
 
         if (SCCMightUnwind && SCCMightReturn)
           break;
       }
     }
   }
 
   // If the SCC doesn't unwind or doesn't throw, note this fact.
   if (!SCCMightUnwind || !SCCMightReturn)
-    for (CallGraphNode *I : SCC) {
-      Function *F = I->getFunction();
-
+    for (Function *F : Functions) {
       if (!SCCMightUnwind && !F->hasFnAttribute(Attribute::NoUnwind)) {
         F->addFnAttr(Attribute::NoUnwind);
         MadeChange = true;
       }
 
       if (!SCCMightReturn && !F->hasFnAttribute(Attribute::NoReturn)) {
         F->addFnAttr(Attribute::NoReturn);
         MadeChange = true;
       }
     }
 
-  for (CallGraphNode *I : SCC) {
+  for (Function *F : Functions) {
     // Convert any invoke instructions to non-throwing functions in this node
     // into call instructions with a branch.  This makes the exception blocks
     // dead.
-    if (Function *F = I->getFunction())
-      MadeChange |= SimplifyFunction(F, CG);
+    MadeChange |= SimplifyFunction(F, CGU);
   }
 
   return MadeChange;
 }
 
-
 bool PruneEH::runOnSCC(CallGraphSCC &SCC) {
   if (skipSCC(SCC))
     return false;
+  SetVector<Function *> Functions;
+  for (auto &N : SCC) {
+    if (auto *F = N->getFunction())
+      Functions.insert(F);
+  }
   CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
-  return runImpl(SCC, CG);
+  CallGraphUpdater CGU;
+  CGU.initialize(CG, SCC);
+  return runImpl(CGU, Functions);
 }
 
 
 // SimplifyFunction - Given information about callees, simplify the specified
 // function if we have invokes to non-unwinding functions or code after calls to
 // no-return functions.
-static bool SimplifyFunction(Function *F, CallGraph &CG) {
+static bool SimplifyFunction(Function *F, CallGraphUpdater &CGU) {
   bool MadeChange = false;
   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
     if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
       if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(F)) {
         BasicBlock *UnwindBlock = II->getUnwindDest();
         removeUnwindEdge(&*BB);
 
         // If the unwind block is now dead, nuke it.
         if (pred_empty(UnwindBlock))
-          DeleteBasicBlock(UnwindBlock, CG);  // Delete the new BB.
+          DeleteBasicBlock(UnwindBlock, CGU); // Delete the new BB.
 
         ++NumRemoved;
         MadeChange = true;
       }
 
     for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
       if (CallInst *CI = dyn_cast<CallInst>(I++))
         if (CI->doesNotReturn() && !CI->isMustTailCall() &&
             !isa<UnreachableInst>(I)) {
           // This call calls a function that cannot return.  Insert an
           // unreachable instruction after it and simplify the code.  Do this
           // by splitting the BB, adding the unreachable, then deleting the
           // new BB.
           BasicBlock *New = BB->splitBasicBlock(I);
 
           // Remove the uncond branch and add an unreachable.
           BB->getInstList().pop_back();
           new UnreachableInst(BB->getContext(), &*BB);
 
-          DeleteBasicBlock(New, CG);  // Delete the new BB.
+          DeleteBasicBlock(New, CGU); // Delete the new BB.
           MadeChange = true;
           ++NumUnreach;
           break;
         }
   }
 
   return MadeChange;
 }
 
 /// DeleteBasicBlock - remove the specified basic block from the program,
 /// updating the callgraph to reflect any now-obsolete edges due to calls that
 /// exist in the BB.
-static void DeleteBasicBlock(BasicBlock *BB, CallGraph &CG) {
+static void DeleteBasicBlock(BasicBlock *BB, CallGraphUpdater &CGU) {
   assert(pred_empty(BB) && "BB is not dead!");
 
   Instruction *TokenInst = nullptr;
 
-  CallGraphNode *CGN = CG[BB->getParent()];
   for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; ) {
     --I;
 
     if (I->getType()->isTokenTy()) {
       TokenInst = &*I;
       break;
     }
 
     if (auto *Call = dyn_cast<CallBase>(&*I)) {
       const Function *Callee = Call->getCalledFunction();
       if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
-        CGN->removeCallEdgeFor(*Call);
+        CGU.removeCallSite(*Call);
       else if (!Callee->isIntrinsic())
-        CGN->removeCallEdgeFor(*Call);
+        CGU.removeCallSite(*Call);
     }
 
     if (!I->use_empty())
       I->replaceAllUsesWith(UndefValue::get(I->getType()));
   }
 
   if (TokenInst) {
     if (!TokenInst->isTerminator())