SimplifyCFG: Clean up optforfuzzing implementation

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

Author: arsenm

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

@@ -66,18 +66,25 @@ struct SimplifyCFGOptions {
   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.
@@ -105,6 +112,15 @@ struct SimplifyCFGOptions {
     AC = Cache;
     return *this;
   }
+  SimplifyCFGOptions &setSimplifyCondBranch(bool B) {
+    SimplifyCondBranch = B;
+    return *this;
+  }
+
+  SimplifyCFGOptions &setFoldTwoEntryPHINode(bool B) {
+    FoldTwoEntryPHINode = B;
+    return *this;
+  }
 };
 
 //===----------------------------------------------------------------------===//

llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp

@@ -281,6 +281,14 @@ struct CFGSimplifyPass : public FunctionPass {
       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);
   }

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -2336,9 +2336,6 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI,
   // 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);
@@ -5969,8 +5966,7 @@ static BasicBlock *allPredecessorsComeFromSameSource(BasicBlock *BB) {
 
 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
@@ -6184,11 +6180,13 @@ bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) {
 
   IRBuilder<> Builder(BB);
 
-  // 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);
+  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);