SimplifyCFG: Clean up optforfuzzing implementation

[arsenm]

Summary

This should function as any other SimplifyCFGOption rather than having
the transform check and specially consider the attribute itself.

[morehouse]

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

6183

Should this go in the FoldTwoEntryPHINode function in case any future calls to the function are added?

[arsenm]

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

6183

I was going with the example of Options.SinkCommonInsts. If you are directly calling FoldTwoEntryPHINode, I would expect it to do as it claims regardless of the option

[arsenm]

cdd006eec9409923f9a56b9026ce2cb72e7b71dc

llvm/include/llvm/Transforms/Utils/Local.h

 /// For example, canonical form that includes switches and branches may later be
 /// replaced by lookup tables and selects.
 struct SimplifyCFGOptions {
   int BonusInstThreshold;
   bool ForwardSwitchCondToPhi;
   bool ConvertSwitchToLookupTable;
   bool NeedCanonicalLoop;
   bool SinkCommonInsts;
+  bool SimplifyCondBranch;
+  bool FoldTwoEntryPHINode;
+
   AssumptionCache *AC;
 
   SimplifyCFGOptions(unsigned BonusThreshold = 1,
                      bool ForwardSwitchCond = false,
                      bool SwitchToLookup = false, bool CanonicalLoops = true,
                      bool SinkCommon = false,
-                     AssumptionCache *AssumpCache = nullptr)
+                     AssumptionCache *AssumpCache = nullptr,
+                     bool SimplifyCondBranch = true,
+                     bool FoldTwoEntryPHINode = true)
       : BonusInstThreshold(BonusThreshold),
         ForwardSwitchCondToPhi(ForwardSwitchCond),
         ConvertSwitchToLookupTable(SwitchToLookup),
         NeedCanonicalLoop(CanonicalLoops),
         SinkCommonInsts(SinkCommon),
+        SimplifyCondBranch(SimplifyCondBranch),
+        FoldTwoEntryPHINode(FoldTwoEntryPHINode),
         AC(AssumpCache) {}
 
   // Support 'builder' pattern to set members by name at construction time.
   SimplifyCFGOptions &bonusInstThreshold(int I) {
     BonusInstThreshold = I;
     return *this;
   }
   SimplifyCFGOptions &forwardSwitchCondToPhi(bool B) {
struct SimplifyCFGOptions {
   SimplifyCFGOptions &sinkCommonInsts(bool B) {
     SinkCommonInsts = B;
     return *this;
   }
   SimplifyCFGOptions &setAssumptionCache(AssumptionCache *Cache) {
     AC = Cache;
     return *this;
   }
+  SimplifyCFGOptions &setSimplifyCondBranch(bool B) {
+    SimplifyCondBranch = B;
+    return *this;
+  }
+
+  SimplifyCFGOptions &setFoldTwoEntryPHINode(bool B) {
+    FoldTwoEntryPHINode = B;
+    return *this;
+  }
 };
 
 //===----------------------------------------------------------------------===//
 //  Local constant propagation.
 //
 
 /// If a terminator instruction is predicated on a constant value, convert it
 /// into an unconditional branch to the constant destination.

llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp

Options.SinkCommonInsts = UserSinkCommonInsts.getNumOccurrences()
                                   : SinkCommon;
   }
 
   bool runOnFunction(Function &F) override {
     if (skipFunction(F) || (PredicateFtor && !PredicateFtor(F)))
       return false;
 
     Options.AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+    if (F.hasFnAttribute(Attribute::OptForFuzzing)) {
+      Options.setSimplifyCondBranch(false)
+             .setFoldTwoEntryPHINode(false);
+    } else {
+      Options.setSimplifyCondBranch(true)
+             .setFoldTwoEntryPHINode(true);
+    }
+
     auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
     return simplifyFunctionCFG(F, TTI, Options);
   }
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<AssumptionCacheTracker>();
     AU.addRequired<TargetTransformInfoWrapperPass>();
     AU.addPreserved<GlobalsAAWrapperPass>();
   }

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI,
                                 const DataLayout &DL) {
   // Ok, this is a two entry PHI node.  Check to see if this is a simple "if
   // statement", which has a very simple dominance structure.  Basically, we
   // are trying to find the condition that is being branched on, which
   // subsequently causes this merge to happen.  We really want control
   // dependence information for this check, but simplifycfg can't keep it up
   // to date, and this catches most of the cases we care about anyway.
   BasicBlock *BB = PN->getParent();
-  const Function *Fn = BB->getParent();
-  if (Fn && Fn->hasFnAttribute(Attribute::OptForFuzzing))
-    return false;
 
   BasicBlock *IfTrue, *IfFalse;
   Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
   if (!IfCond ||
       // Don't bother if the branch will be constant folded trivially.
       isa<ConstantInt>(IfCond))
     return false;
 
if (!PPred || (PredPred && PredPred != PPred))
       return nullptr;
     PredPred = PPred;
   }
   return PredPred;
 }
 
 bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
   BasicBlock *BB = BI->getParent();
-  const Function *Fn = BB->getParent();
-  if (Fn && Fn->hasFnAttribute(Attribute::OptForFuzzing))
+  if (!Options.SimplifyCondBranch)
     return false;
 
   // Conditional branch
   if (isValueEqualityComparison(BI)) {
     // If we only have one predecessor, and if it is a branch on this value,
     // see if that predecessor totally determines the outcome of this
     // switch.
     if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) {
   if (MergeBlockIntoPredecessor(BB))
     return true;
 
   if (SinkCommon && Options.SinkCommonInsts)
     Changed |= SinkCommonCodeFromPredecessors(BB);
 
   IRBuilder<> Builder(BB);
 
+  if (Options.FoldTwoEntryPHINode) {
     // If there is a trivial two-entry PHI node in this basic block, and we can
     // eliminate it, do so now.
     if (auto *PN = dyn_cast<PHINode>(BB->begin()))
       if (PN->getNumIncomingValues() == 2)
         Changed |= FoldTwoEntryPHINode(PN, TTI, DL);
+  }
 
   Instruction *Terminator = BB->getTerminator();
   Builder.SetInsertPoint(Terminator);
   switch (Terminator->getOpcode()) {
   case Instruction::Br:
     Changed |= simplifyBranch(cast<BranchInst>(Terminator), Builder);
     break;
   case Instruction::Ret: