llvm-reduce: Use simpleSimplifyCFG in block reduction (#135028)

Author: arsenm

llvm/test/tools/llvm-reduce/remove-bb-switch-default.ll

@@ -16,6 +16,7 @@
 ; RESULT0-NEXT: br i1 %arg0, label %bb1, label %bb2
 
 ; RESULT0: bb1:
+; RESULT0: %bb1.phi = phi i32 [ %bb.load, %bb ], [ %bb.load, %bb2 ], [ %bb.load, %bb2 ]
 ; RESULT0-NEXT: store i32 1, ptr null, align 4
 ; RESULT0-NEXT: ret void
 

llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp

@@ -31,9 +31,11 @@
 
 using namespace llvm;
 
+using BlockSet = SetVector<BasicBlock *>;
+
 /// Replaces BB Terminator with one that only contains Chunk BBs
 static void replaceBranchTerminator(BasicBlock &BB,
-                                    const DenseSet<BasicBlock *> &BBsToDelete) {
+                                    const BlockSet &BBsToDelete) {
   auto *Term = BB.getTerminator();
   std::vector<BasicBlock *> ChunkSuccessors;
   for (auto *Succ : successors(&BB)) {
@@ -104,9 +106,8 @@ static void replaceBranchTerminator(BasicBlock &BB,
 /// Removes uninteresting BBs from switch, if the default case ends up being
 /// uninteresting, the switch is replaced with a void return (since it has to be
 /// replace with something)
-static void
-removeUninterestingBBsFromSwitch(SwitchInst &SwInst,
-                                 const DenseSet<BasicBlock *> &BBsToDelete) {
+static void removeUninterestingBBsFromSwitch(SwitchInst &SwInst,
+                                             const BlockSet &BBsToDelete) {
   for (int I = 0, E = SwInst.getNumCases(); I != E; ++I) {
     auto Case = SwInst.case_begin() + I;
     if (BBsToDelete.count(Case->getCaseSuccessor())) {
@@ -142,7 +143,8 @@ removeUninterestingBBsFromSwitch(SwitchInst &SwInst,
 /// Removes out-of-chunk arguments from functions, and modifies their calls
 /// accordingly. It also removes allocations of out-of-chunk arguments.
 void llvm::reduceBasicBlocksDeltaPass(Oracle &O, ReducerWorkItem &WorkItem) {
-  DenseSet<BasicBlock *> BBsToDelete;
+  BlockSet BBsToDelete;
+
   df_iterator_default_set<BasicBlock *> Reachable;
 
   for (auto &F : WorkItem.getModule()) {
@@ -183,7 +185,8 @@ void llvm::reduceBasicBlocksDeltaPass(Oracle &O, ReducerWorkItem &WorkItem) {
     // Cleanup any blocks that are now dead after eliminating this set. This
     // will likely be larger than the number of blocks the oracle told us to
     // delete.
-    EliminateUnreachableBlocks(F);
+    simpleSimplifyCFG(F, BBsToDelete.getArrayRef());
+
     BBsToDelete.clear();
   }
 }