From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Sat, 7 Feb 2015 21:37:08 +0000 (+0000)
Subject: LoopIdiom: Use utility functions.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fd3cd51a3a884969b30dee728cf0c1322dc4e9d1;p=oota-llvm.git

LoopIdiom: Use utility functions.

The only difference between deleteIfDeadInstruction and
RecursivelyDeleteTriviallyDeadInstructions is that the former also
manually invalidates SCEV. That's unnecessary because SCEV automatically
gets informed when an instruction is deleted via a ValueHandle. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228508 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 14984a9a587..243c624fc4b 100644
--- a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -237,44 +237,13 @@ Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); }
 /// and zero out all the operands of this instruction.  If any of them become
 /// dead, delete them and the computation tree that feeds them.
 ///
-static void deleteDeadInstruction(Instruction *I, ScalarEvolution &SE,
+static void deleteDeadInstruction(Instruction *I,
                                   const TargetLibraryInfo *TLI) {
-  SmallVector<Instruction*, 32> NowDeadInsts;
-
-  NowDeadInsts.push_back(I);
-
-  // Before we touch this instruction, remove it from SE!
-  do {
-    Instruction *DeadInst = NowDeadInsts.pop_back_val();
-
-    // This instruction is dead, zap it, in stages.  Start by removing it from
-    // SCEV.
-    SE.forgetValue(DeadInst);
-
-    for (unsigned op = 0, e = DeadInst->getNumOperands(); op != e; ++op) {
-      Value *Op = DeadInst->getOperand(op);
-      DeadInst->setOperand(op, nullptr);
-
-      // If this operand just became dead, add it to the NowDeadInsts list.
-      if (!Op->use_empty()) continue;
-
-      if (Instruction *OpI = dyn_cast<Instruction>(Op))
-        if (isInstructionTriviallyDead(OpI, TLI))
-          NowDeadInsts.push_back(OpI);
-    }
-
-    DeadInst->eraseFromParent();
-
-  } while (!NowDeadInsts.empty());
-}
-
-/// deleteIfDeadInstruction - If the specified value is a dead instruction,
-/// delete it and any recursively used instructions.
-static void deleteIfDeadInstruction(Value *V, ScalarEvolution &SE,
-                                    const TargetLibraryInfo *TLI) {
-  if (Instruction *I = dyn_cast<Instruction>(V))
-    if (isInstructionTriviallyDead(I, TLI))
-      deleteDeadInstruction(I, SE, TLI);
+  SmallVector<Value *, 16> Operands(I->value_op_begin(), I->value_op_end());
+  I->replaceAllUsesWith(UndefValue::get(I->getType()));
+  I->eraseFromParent();
+  for (Value *Op : Operands)
+    RecursivelyDeleteTriviallyDeadInstructions(Op, TLI);
 }
 
 //===----------------------------------------------------------------------===//
@@ -290,7 +259,7 @@ static void deleteIfDeadInstruction(Value *V, ScalarEvolution &SE,
 // the concern of breaking data dependence.
 bool LIRUtil::isAlmostEmpty(BasicBlock *BB) {
   if (BranchInst *Br = getBranch(BB)) {
-    return Br->isUnconditional() && BB->size() == 1;
+    return Br->isUnconditional() && Br == BB->begin();
   }
   return false;
 }
@@ -547,7 +516,7 @@ void NclPopcountRecognize::transform(Instruction *CntInst,
       cast<ICmpInst>(Builder.CreateICmp(PreCond->getPredicate(), Opnd0, Opnd1));
     PreCond->replaceAllUsesWith(NewPreCond);
 
-    deleteDeadInstruction(PreCond, *SE, TLI);
+    RecursivelyDeleteTriviallyDeadInstructions(PreCond, TLI);
   }
 
   // Step 3: Note that the population count is exactly the trip count of the
@@ -597,15 +566,7 @@ void NclPopcountRecognize::transform(Instruction *CntInst,
   // Step 4: All the references to the original population counter outside
   //  the loop are replaced with the NewCount -- the value returned from
   //  __builtin_ctpop().
-  {
-    SmallVector<Value *, 4> CntUses;
-    for (User *U : CntInst->users())
-      if (cast<Instruction>(U)->getParent() != Body)
-        CntUses.push_back(U);
-    for (unsigned Idx = 0; Idx < CntUses.size(); Idx++) {
-      (cast<Instruction>(CntUses[Idx]))->replaceUsesOfWith(CntInst, NewCount);
-    }
-  }
+  CntInst->replaceUsesOutsideBlock(NewCount, Body);
 
   // step 5: Forget the "non-computable" trip-count SCEV associated with the
   //   loop. The loop would otherwise not be deleted even if it becomes empty.
@@ -1002,7 +963,7 @@ processLoopStridedStore(Value *DestPtr, unsigned StoreSize,
                             StoreSize, getAnalysis<AliasAnalysis>(), TheStore)) {
     Expander.clear();
     // If we generated new code for the base pointer, clean up.
-    deleteIfDeadInstruction(BasePtr, *SE, TLI);
+    RecursivelyDeleteTriviallyDeadInstructions(BasePtr, TLI);
     return false;
   }
 
@@ -1058,7 +1019,7 @@ processLoopStridedStore(Value *DestPtr, unsigned StoreSize,
 
   // Okay, the memset has been formed.  Zap the original store and anything that
   // feeds into it.
-  deleteDeadInstruction(TheStore, *SE, TLI);
+  deleteDeadInstruction(TheStore, TLI);
   ++NumMemSet;
   return true;
 }
@@ -1099,7 +1060,7 @@ processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize,
                             getAnalysis<AliasAnalysis>(), SI)) {
     Expander.clear();
     // If we generated new code for the base pointer, clean up.
-    deleteIfDeadInstruction(StoreBasePtr, *SE, TLI);
+    RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
     return false;
   }
 
@@ -1114,8 +1075,8 @@ processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize,
                             StoreSize, getAnalysis<AliasAnalysis>(), SI)) {
     Expander.clear();
     // If we generated new code for the base pointer, clean up.
-    deleteIfDeadInstruction(LoadBasePtr, *SE, TLI);
-    deleteIfDeadInstruction(StoreBasePtr, *SE, TLI);
+    RecursivelyDeleteTriviallyDeadInstructions(LoadBasePtr, TLI);
+    RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
     return false;
   }
 
@@ -1148,7 +1109,7 @@ processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize,
 
   // Okay, the memset has been formed.  Zap the original store and anything that
   // feeds into it.
-  deleteDeadInstruction(SI, *SE, TLI);
+  deleteDeadInstruction(SI, TLI);
   ++NumMemCpy;
   return true;
 }