Revert "[SimplifyCFG] accumulate bonus insts cost"

This reverts commit e5581df60a35fffb0c69589777e4e126c849405f.

This causes major compile-time regressions, about 2-3% end-to-end
on CTMark.

1 files changed, 19 insertions, 44 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 755f4be..fcdd858 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -207,21 +207,6 @@ STATISTIC(NumInvokes,
 STATISTIC(NumInvokesMerged, "Number of invokes that were merged together");
 STATISTIC(NumInvokeSetsFormed, "Number of invoke sets that were formed");
 
-namespace llvm {
-
-void SimplifyCFGCostTracker::updateNumBonusInsts(BasicBlock *BB,
-                                                 unsigned InstCount) {
-  auto Loc = NumBonusInsts.find(BB);
-  if (Loc == NumBonusInsts.end())
-    Loc = NumBonusInsts.insert({BB, 0}).first;
-  Loc->second = Loc->second + InstCount;
-}
-unsigned SimplifyCFGCostTracker::getNumBonusInsts(BasicBlock *BB) {
-  return NumBonusInsts.lookup(BB);
-}
-
-} // namespace llvm
-
 namespace {
 
 // The first field contains the value that the switch produces when a certain
@@ -258,10 +243,6 @@ class SimplifyCFGOpt {
   ArrayRef<WeakVH> LoopHeaders;
   const SimplifyCFGOptions &Options;
   bool Resimplify;
-  // Accumulates number of bonus instructions due to merging basic blocks
-  // of common destination.
-  SimplifyCFGCostTracker *CostTracker;
-  SimplifyCFGCostTracker LocalCostTracker;
 
   Value *isValueEqualityComparison(Instruction *TI);
   BasicBlock *GetValueEqualityComparisonCases(
@@ -305,10 +286,8 @@ class SimplifyCFGOpt {
 public:
   SimplifyCFGOpt(const TargetTransformInfo &TTI, DomTreeUpdater *DTU,
                  const DataLayout &DL, ArrayRef<WeakVH> LoopHeaders,
-                 const SimplifyCFGOptions &Opts,
-                 SimplifyCFGCostTracker *CostTracker_)
-      : TTI(TTI), DTU(DTU), DL(DL), LoopHeaders(LoopHeaders), Options(Opts),
-        CostTracker(CostTracker_ ? CostTracker_ : &LocalCostTracker) {
+                 const SimplifyCFGOptions &Opts)
+      : TTI(TTI), DTU(DTU), DL(DL), LoopHeaders(LoopHeaders), Options(Opts) {
     assert((!DTU || !DTU->hasPostDomTree()) &&
            "SimplifyCFG is not yet capable of maintaining validity of a "
            "PostDomTree, so don't ask for it.");
@@ -3645,9 +3624,8 @@ static bool isVectorOp(Instruction &I) {
 /// If this basic block is simple enough, and if a predecessor branches to us
 /// and one of our successors, fold the block into the predecessor and use
 /// logical operations to pick the right destination.
-bool llvm::FoldBranchToCommonDest(BranchInst *BI,
-                                  SimplifyCFGCostTracker &CostTracker,
-                                  DomTreeUpdater *DTU, MemorySSAUpdater *MSSAU,
+bool llvm::FoldBranchToCommonDest(BranchInst *BI, DomTreeUpdater *DTU,
+                                  MemorySSAUpdater *MSSAU,
                                   const TargetTransformInfo *TTI,
                                   unsigned BonusInstThreshold) {
   // If this block ends with an unconditional branch,
@@ -3719,6 +3697,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI,
   // as "bonus instructions", and only allow this transformation when the
   // number of the bonus instructions we'll need to create when cloning into
   // each predecessor does not exceed a certain threshold.
+  unsigned NumBonusInsts = 0;
   bool SawVectorOp = false;
   const unsigned PredCount = Preds.size();
   for (Instruction &I : *BB) {
@@ -3737,13 +3716,12 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI,
     // predecessor. Ignore free instructions.
     if (!TTI || TTI->getInstructionCost(&I, CostKind) !=
                     TargetTransformInfo::TCC_Free) {
-      for (auto PredBB : Preds) {
-        CostTracker.updateNumBonusInsts(PredBB, PredCount);
-        // Early exits once we reach the limit.
-        if (CostTracker.getNumBonusInsts(PredBB) >
-            BonusInstThreshold * BranchFoldToCommonDestVectorMultiplier)
-          return false;
-      }
+      NumBonusInsts += PredCount;
+
+      // Early exits once we reach the limit.
+      if (NumBonusInsts >
+          BonusInstThreshold * BranchFoldToCommonDestVectorMultiplier)
+        return false;
     }
 
     auto IsBCSSAUse = [BB, &I](Use &U) {
@@ -3757,12 +3735,10 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI,
     if (!all_of(I.uses(), IsBCSSAUse))
       return false;
   }
-  for (auto PredBB : Preds) {
-    if (CostTracker.getNumBonusInsts(PredBB) >
-        BonusInstThreshold *
-            (SawVectorOp ? BranchFoldToCommonDestVectorMultiplier : 1))
-      return false;
-  }
+  if (NumBonusInsts >
+      BonusInstThreshold *
+          (SawVectorOp ? BranchFoldToCommonDestVectorMultiplier : 1))
+    return false;
 
   // Ok, we have the budget. Perform the transformation.
   for (BasicBlock *PredBlock : Preds) {
@@ -6913,7 +6889,7 @@ bool SimplifyCFGOpt::simplifyUncondBranch(BranchInst *BI,
   // branches to us and our successor, fold the comparison into the
   // predecessor and use logical operations to update the incoming value
   // for PHI nodes in common successor.
-  if (FoldBranchToCommonDest(BI, *CostTracker, DTU, /*MSSAU=*/nullptr, &TTI,
+  if (FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
                              Options.BonusInstThreshold))
     return requestResimplify();
   return false;
@@ -6982,7 +6958,7 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
   // If this basic block is ONLY a compare and a branch, and if a predecessor
   // branches to us and one of our successors, fold the comparison into the
   // predecessor and use logical operations to pick the right destination.
-  if (FoldBranchToCommonDest(BI, *CostTracker, DTU, /*MSSAU=*/nullptr, &TTI,
+  if (FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
                              Options.BonusInstThreshold))
     return requestResimplify();
 
@@ -7281,9 +7257,8 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
 
 bool llvm::simplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
                        DomTreeUpdater *DTU, const SimplifyCFGOptions &Options,
-                       ArrayRef<WeakVH> LoopHeaders,
-                       SimplifyCFGCostTracker *CostTracker) {
+                       ArrayRef<WeakVH> LoopHeaders) {
   return SimplifyCFGOpt(TTI, DTU, BB->getModule()->getDataLayout(), LoopHeaders,
-                        Options, CostTracker)
+                        Options)
       .run(BB);
 }