[llvm] 9d7785b - [BasicBlockUtils][NFCI] Extract branch inverting to a separate method

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2023-04-21T19:44:13+07:00
New Revision: 9d7785b2e99548f3fde6fa030443a4d443dec647

URL: https://github.com/llvm/llvm-project/commit/9d7785b2e99548f3fde6fa030443a4d443dec647
DIFF: https://github.com/llvm/llvm-project/commit/9d7785b2e99548f3fde6fa030443a4d443dec647.diff

LOG: [BasicBlockUtils][NFCI] Extract branch inverting to a separate method

The motivation is to make possible branch inverting code reuse.

Patch by Aleksandr Popov!

Differential Revision: https://reviews.llvm.org/D148708

Added: 
    

Modified: 
    llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
    llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
    llvm/lib/Transforms/Utils/FlattenCFG.cpp
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h b/llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
index bc1bba1ff59a..74501e0244aa 100644
--- a/llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
@@ -605,6 +605,10 @@ BasicBlock *CreateControlFlowHub(
     const SetVector<BasicBlock *> &Successors, const StringRef Prefix,
     std::optional<unsigned> MaxControlFlowBooleans = std::nullopt);
 
+// Utility function for inverting branch condition and for swapping its
+// successors
+void InvertBranch(BranchInst *PBI, IRBuilderBase &Builder);
+
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H

diff  --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index f0e24650cd5e..7509c482ee32 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -2049,3 +2049,17 @@ BasicBlock *llvm::CreateControlFlowHub(
 
   return FirstGuardBlock;
 }
+
+void llvm::InvertBranch(BranchInst *PBI, IRBuilderBase &Builder) {
+  Value *NewCond = PBI->getCondition();
+  // If this is a "cmp" instruction, only used for branching (and nowhere
+  // else), then we can simply invert the predicate.
+  if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) {
+    CmpInst *CI = cast<CmpInst>(NewCond);
+    CI->setPredicate(CI->getInversePredicate());
+  } else
+    NewCond = Builder.CreateNot(NewCond, NewCond->getName() + ".not");
+
+  PBI->setCondition(NewCond);
+  PBI->swapSuccessors();
+}

diff  --git a/llvm/lib/Transforms/Utils/FlattenCFG.cpp b/llvm/lib/Transforms/Utils/FlattenCFG.cpp
index 58ececd16a66..1925b91c4da7 100644
--- a/llvm/lib/Transforms/Utils/FlattenCFG.cpp
+++ b/llvm/lib/Transforms/Utils/FlattenCFG.cpp
@@ -487,16 +487,9 @@ bool FlattenCFGOpt::MergeIfRegion(BasicBlock *BB, IRBuilder<> &Builder) {
   BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
   Builder.SetInsertPoint(PBI);
   if (InvertCond2) {
-    // If this is a "cmp" instruction, only used for branching (and nowhere
-    // else), then we can simply invert the predicate.
-    auto Cmp2 = dyn_cast<CmpInst>(CInst2);
-    if (Cmp2 && Cmp2->hasOneUse())
-      Cmp2->setPredicate(Cmp2->getInversePredicate());
-    else
-      CInst2 = cast<Instruction>(Builder.CreateNot(CInst2));
-    PBI->swapSuccessors();
+    InvertBranch(PBI, Builder);
   }
-  Value *NC = Builder.CreateBinOp(CombineOp, CInst1, CInst2);
+  Value *NC = Builder.CreateBinOp(CombineOp, CInst1, PBI->getCondition());
   PBI->replaceUsesOfWith(PBI->getCondition(), NC);
   Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt);
 

diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 137fdf192831..cbfd7b7fe860 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3580,17 +3580,7 @@ static bool performBranchToCommonDestFolding(BranchInst *BI, BranchInst *PBI,
 
   // If we need to invert the condition in the pred block to match, do so now.
   if (InvertPredCond) {
-    Value *NewCond = PBI->getCondition();
-    if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) {
-      CmpInst *CI = cast<CmpInst>(NewCond);
-      CI->setPredicate(CI->getInversePredicate());
-    } else {
-      NewCond =
-          Builder.CreateNot(NewCond, PBI->getCondition()->getName() + ".not");
-    }
-
-    PBI->setCondition(NewCond);
-    PBI->swapSuccessors();
+    InvertBranch(PBI, Builder);
   }
 
   BasicBlock *UniqueSucc =