[llvm] r354107 - [NFC] Tweak SplitBlockAndInsertIfThen to use existing ThenBlock

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Fri Feb 15 00:18:00 2019
New Revision: 354107

URL: http://llvm.org/viewvc/llvm-project?rev=354107&view=rev
Log:
[NFC] Tweak SplitBlockAndInsertIfThen to use existing ThenBlock

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

Modified: llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h?rev=354107&r1=354106&r2=354107&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h Fri Feb 15 00:18:00 2019
@@ -270,7 +270,8 @@ ReturnInst *FoldReturnIntoUncondBranch(R
 ///   SplitBefore
 ///   Tail
 ///
-/// If Unreachable is true, then ThenBlock ends with
+/// If \p ThenBlock is not specified, a new block will be created for it.
+/// If \p Unreachable is true, the newly created block will end with
 /// UnreachableInst, otherwise it branches to Tail.
 /// Returns the NewBasicBlock's terminator.
 ///
@@ -279,7 +280,8 @@ Instruction *SplitBlockAndInsertIfThen(V
                                        bool Unreachable,
                                        MDNode *BranchWeights = nullptr,
                                        DominatorTree *DT = nullptr,
-                                       LoopInfo *LI = nullptr);
+                                       LoopInfo *LI = nullptr,
+                                       BasicBlock *ThenBlock = nullptr);
 
 /// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen,
 /// but also creates the ElseBlock.

Modified: llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp?rev=354107&r1=354106&r2=354107&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp Fri Feb 15 00:18:00 2019
@@ -730,18 +730,23 @@ Instruction *llvm::SplitBlockAndInsertIf
                                              Instruction *SplitBefore,
                                              bool Unreachable,
                                              MDNode *BranchWeights,
-                                             DominatorTree *DT, LoopInfo *LI) {
+                                             DominatorTree *DT, LoopInfo *LI,
+                                             BasicBlock *ThenBlock) {
   BasicBlock *Head = SplitBefore->getParent();
   BasicBlock *Tail = Head->splitBasicBlock(SplitBefore->getIterator());
   Instruction *HeadOldTerm = Head->getTerminator();
   LLVMContext &C = Head->getContext();
-  BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
   Instruction *CheckTerm;
-  if (Unreachable)
-    CheckTerm = new UnreachableInst(C, ThenBlock);
-  else
-    CheckTerm = BranchInst::Create(Tail, ThenBlock);
-  CheckTerm->setDebugLoc(SplitBefore->getDebugLoc());
+  bool CreateThenBlock = (ThenBlock == nullptr);
+  if (CreateThenBlock) {
+    ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
+    if (Unreachable)
+      CheckTerm = new UnreachableInst(C, ThenBlock);
+    else
+      CheckTerm = BranchInst::Create(Tail, ThenBlock);
+    CheckTerm->setDebugLoc(SplitBefore->getDebugLoc());
+  } else
+    CheckTerm = ThenBlock->getTerminator();
   BranchInst *HeadNewTerm =
     BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cond);
   HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
@@ -756,7 +761,10 @@ Instruction *llvm::SplitBlockAndInsertIf
         DT->changeImmediateDominator(Child, NewNode);
 
       // Head dominates ThenBlock.
-      DT->addNewBlock(ThenBlock, Head);
+      if (CreateThenBlock)
+        DT->addNewBlock(ThenBlock, Head);
+      else
+        DT->changeImmediateDominator(ThenBlock, Head);
     }
   }