Replace the old ADCE implementation with a new one that more simply solves

the one case that ADCE catches that normal DCE doesn't: non-induction variable
loop computations.

This implementation handles this problem without using postdominators.

llvm-svn: 51668

3 files changed, 62 insertions, 501 deletions

diff --git a/llvm/lib/Transforms/Scalar/ADCE.cpp b/llvm/lib/Transforms/Scalar/ADCE.cpp
index 11fb1e33242..5c3b833452b 100644
--- a/llvm/lib/Transforms/Scalar/ADCE.cpp
+++ b/llvm/lib/Transforms/Scalar/ADCE.cpp
@@ -1,4 +1,4 @@
-//===- ADCE.cpp - Code to perform aggressive dead code elimination --------===//
+//===- DCE.cpp - Code to perform dead code elimination --------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,481 +7,86 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements "aggressive" dead code elimination.  ADCE is DCe where
-// values are assumed to be dead until proven otherwise.  This is similar to
-// SCCP, except applied to the liveness of values.
+// This file implements the Aggressive Dead Code Elimination pass.  This pass
+// optimistically assumes that all instructions are dead until proven otherwise,
+// allowing it to eliminate dead computations that other DCE passes do not 
+// catch, particularly involving loop computations.
 //
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "adce"
 #include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
 #include "llvm/Instructions.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/PostDominators.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/Pass.h"
 #include "llvm/Support/Compiler.h"
-#include <algorithm>
+#include "llvm/Support/InstIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SmallPtrSet.h"
+
 using namespace llvm;
 
-STATISTIC(NumBlockRemoved, "Number of basic blocks removed");
-STATISTIC(NumInstRemoved , "Number of instructions removed");
-STATISTIC(NumCallRemoved , "Number of calls removed");
+STATISTIC(NumRemoved, "Number of instructions removed");
 
 namespace {
-//===----------------------------------------------------------------------===//
-// ADCE Class
-//
-// This class does all of the work of Aggressive Dead Code Elimination.
-// It's public interface consists of a constructor and a doADCE() method.
-//
-class VISIBILITY_HIDDEN ADCE : public FunctionPass {
-  Function *Func;                       // The function that we are working on
-  std::vector<Instruction*> WorkList;   // Instructions that just became live
-  std::set<Instruction*>    LiveSet;    // The set of live instructions
-
-  //===--------------------------------------------------------------------===//
-  // The public interface for this class
-  //
-public:
-  static char ID; // Pass identification, replacement for typeid
-  ADCE() : FunctionPass((intptr_t)&ID) {}
-
-  // Execute the Aggressive Dead Code Elimination Algorithm
-  //
-  virtual bool runOnFunction(Function &F) {
-    Func = &F;
-    bool Changed = doADCE();
-    assert(WorkList.empty());
-    LiveSet.clear();
-    return Changed;
-  }
-  // getAnalysisUsage - We require post dominance frontiers (aka Control
-  // Dependence Graph)
-  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-    // We require that all function nodes are unified, because otherwise code
-    // can be marked live that wouldn't necessarily be otherwise.
-    AU.addRequired<UnifyFunctionExitNodes>();
-    AU.addRequired<AliasAnalysis>();
-    AU.addRequired<PostDominatorTree>();
-    AU.addRequired<PostDominanceFrontier>();
-  }
-
-
-  //===--------------------------------------------------------------------===//
-  // The implementation of this class
-  //
-private:
-  // doADCE() - Run the Aggressive Dead Code Elimination algorithm, returning
-  // true if the function was modified.
-  //
-  bool doADCE();
-
-  void markBlockAlive(BasicBlock *BB);
-
-
-  // deleteDeadInstructionsInLiveBlock - Loop over all of the instructions in
-  // the specified basic block, deleting ones that are dead according to
-  // LiveSet.
-  bool deleteDeadInstructionsInLiveBlock(BasicBlock *BB);
-
-  TerminatorInst *convertToUnconditionalBranch(TerminatorInst *TI);
-
-  inline void markInstructionLive(Instruction *I) {
-    if (!LiveSet.insert(I).second) return;
-    DOUT << "Insn Live: " << *I;
-    WorkList.push_back(I);
-  }
-
-  inline void markTerminatorLive(const BasicBlock *BB) {
-    DOUT << "Terminator Live: " << *BB->getTerminator();
-    markInstructionLive(const_cast<TerminatorInst*>(BB->getTerminator()));
-  }
-};
-} // End of anonymous namespace
-
-char ADCE::ID = 0;
-static RegisterPass<ADCE> X("adce", "Aggressive Dead Code Elimination");
-
-FunctionPass *llvm::createAggressiveDCEPass() { return new ADCE(); }
-
-void ADCE::markBlockAlive(BasicBlock *BB) {
-  // Mark the basic block as being newly ALIVE... and mark all branches that
-  // this block is control dependent on as being alive also...
-  //
-  PostDominanceFrontier &CDG = getAnalysis<PostDominanceFrontier>();
-
-  PostDominanceFrontier::const_iterator It = CDG.find(BB);
-  if (It != CDG.end()) {
-    // Get the blocks that this node is control dependent on...
-    const PostDominanceFrontier::DomSetType &CDB = It->second;
-    for (PostDominanceFrontier::DomSetType::const_iterator I =
-           CDB.begin(), E = CDB.end(); I != E; ++I)
-      markTerminatorLive(*I);   // Mark all their terminators as live
-  }
-
-  // If this basic block is live, and it ends in an unconditional branch, then
-  // the branch is alive as well...
-  if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()))
-    if (BI->isUnconditional())
-      markTerminatorLive(BB);
-}
-
-// deleteDeadInstructionsInLiveBlock - Loop over all of the instructions in the
-// specified basic block, deleting ones that are dead according to LiveSet.
-bool ADCE::deleteDeadInstructionsInLiveBlock(BasicBlock *BB) {
-  bool Changed = false;
-  for (BasicBlock::iterator II = BB->begin(), E = --BB->end(); II != E; ) {
-    Instruction *I = II++;
-    if (!LiveSet.count(I)) {              // Is this instruction alive?
-      if (!I->use_empty())
-        I->replaceAllUsesWith(UndefValue::get(I->getType()));
-
-      // Nope... remove the instruction from it's basic block...
-      if (isa<CallInst>(I))
-        ++NumCallRemoved;
-      else
-        ++NumInstRemoved;
-      BB->getInstList().erase(I);
-      Changed = true;
+  struct VISIBILITY_HIDDEN ADCE : public FunctionPass {
+    static char ID; // Pass identification, replacement for typeid
+    ADCE() : FunctionPass((intptr_t)&ID) {}
+    
+    virtual bool runOnFunction(Function& F);
+    
+    virtual void getAnalysisUsage(AnalysisUsage& AU) const {
+      AU.setPreservesCFG();
     }
-  }
-  return Changed;
-}
-
-
-/// convertToUnconditionalBranch - Transform this conditional terminator
-/// instruction into an unconditional branch because we don't care which of the
-/// successors it goes to.  This eliminate a use of the condition as well.
-///
-TerminatorInst *ADCE::convertToUnconditionalBranch(TerminatorInst *TI) {
-  BranchInst *NB = BranchInst::Create(TI->getSuccessor(0), TI);
-  BasicBlock *BB = TI->getParent();
-
-  // Remove entries from PHI nodes to avoid confusing ourself later...
-  for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i)
-    TI->getSuccessor(i)->removePredecessor(BB);
-
-  // Delete the old branch itself...
-  BB->getInstList().erase(TI);
-  return NB;
+    
+  };
 }
 
+char ADCE::ID = 0;
+static RegisterPass<ADCE> X("adce", "Aggressive Dead Code Elimination");
 
-// doADCE() - Run the Aggressive Dead Code Elimination algorithm, returning
-// true if the function was modified.
-//
-bool ADCE::doADCE() {
-  bool MadeChanges = false;
-
-  AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
-
-  // Iterate over all of the instructions in the function, eliminating trivially
-  // dead instructions, and marking instructions live that are known to be
-  // needed.  Perform the walk in depth first order so that we avoid marking any
-  // instructions live in basic blocks that are unreachable.  These blocks will
-  // be eliminated later, along with the instructions inside.
-  //
-  std::set<BasicBlock*> ReachableBBs;
-  std::vector<BasicBlock*> Stack;
-  Stack.push_back(&Func->getEntryBlock());
+bool ADCE::runOnFunction(Function& F) {
+  SmallPtrSet<Instruction*, 32> alive;
+  std::vector<Instruction*> worklist;
   
-  while (!Stack.empty()) {
-    BasicBlock* BB = Stack.back();
-    if (ReachableBBs.count(BB)) {
-      Stack.pop_back();
-      continue;
-    } else {
-      ReachableBBs.insert(BB);
-    }
-    
-    for (BasicBlock::iterator II = BB->begin(), EI = BB->end(); II != EI; ) {
-      Instruction *I = II++;
-      if (CallInst *CI = dyn_cast<CallInst>(I)) {
-        if (AA.onlyReadsMemory(CI)) {
-          if (CI->use_empty()) {
-            BB->getInstList().erase(CI);
-            ++NumCallRemoved;
-          }
-        } else {
-          markInstructionLive(I);
-        }
-      } else if (I->mayWriteToMemory() || isa<ReturnInst>(I) ||
-                 isa<UnwindInst>(I) || isa<UnreachableInst>(I)) {
-        // FIXME: Unreachable instructions should not be marked intrinsically
-        // live here.
-        markInstructionLive(I);
-      } else if (isInstructionTriviallyDead(I)) {
-        // Remove the instruction from it's basic block...
-        BB->getInstList().erase(I);
-        ++NumInstRemoved;
-      }
+  // Collect the set of "root" instructions that are known live.
+  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
+    if (isa<TerminatorInst>(I.getInstructionIterator()) ||
+        I->mayWriteToMemory()) {
+      alive.insert(I.getInstructionIterator());
+      worklist.push_back(I.getInstructionIterator());
     }
   
-    for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) {
-      // Back edges (as opposed to cross edges) indicate loops, so implicitly
-      // mark them live.
-      if (std::find(Stack.begin(), Stack.end(), *SI) != Stack.end())
-        markInstructionLive(BB->getTerminator());
-      if (!ReachableBBs.count(*SI))
-        Stack.push_back(*SI);
-    }
-  }
-
-  // Check to ensure we have an exit node for this CFG.  If we don't, we won't
-  // have any post-dominance information, thus we cannot perform our
-  // transformations safely.
-  //
-  PostDominatorTree &DT = getAnalysis<PostDominatorTree>();
-  if (DT[&Func->getEntryBlock()] == 0) {
-    WorkList.clear();
-    return MadeChanges;
-  }
-
-  // Scan the function marking blocks without post-dominance information as
-  // live.  Blocks without post-dominance information occur when there is an
-  // infinite loop in the program.  Because the infinite loop could contain a
-  // function which unwinds, exits or has side-effects, we don't want to delete
-  // the infinite loop or those blocks leading up to it.
-  for (Function::iterator I = Func->begin(), E = Func->end(); I != E; ++I)
-    if (DT[I] == 0 && ReachableBBs.count(I))
-      for (pred_iterator PI = pred_begin(I), E = pred_end(I); PI != E; ++PI)
-        markInstructionLive((*PI)->getTerminator());
-
-  DOUT << "Processing work list\n";
-
-  // AliveBlocks - Set of basic blocks that we know have instructions that are
-  // alive in them...
-  //
-  std::set<BasicBlock*> AliveBlocks;
-
-  // Process the work list of instructions that just became live... if they
-  // became live, then that means that all of their operands are necessary as
-  // well... make them live as well.
-  //
-  while (!WorkList.empty()) {
-    Instruction *I = WorkList.back(); // Get an instruction that became live...
-    WorkList.pop_back();
-
-    BasicBlock *BB = I->getParent();
-    if (!ReachableBBs.count(BB)) continue;
-    if (AliveBlocks.insert(BB).second)     // Basic block not alive yet.
-      markBlockAlive(BB);             // Make it so now!
-
-    // PHI nodes are a special case, because the incoming values are actually
-    // defined in the predecessor nodes of this block, meaning that the PHI
-    // makes the predecessors alive.
-    //
-    if (PHINode *PN = dyn_cast<PHINode>(I)) {
-      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
-        // If the incoming edge is clearly dead, it won't have control
-        // dependence information.  Do not mark it live.
-        BasicBlock *PredBB = PN->getIncomingBlock(i);
-        if (ReachableBBs.count(PredBB)) {
-          // FIXME: This should mark the control dependent edge as live, not
-          // necessarily the predecessor itself!
-          if (AliveBlocks.insert(PredBB).second)
-            markBlockAlive(PN->getIncomingBlock(i));   // Block is newly ALIVE!
-          if (Instruction *Op = dyn_cast<Instruction>(PN->getIncomingValue(i)))
-            markInstructionLive(Op);
-        }
-      }
-    } else {
-      // Loop over all of the operands of the live instruction, making sure that
-      // they are known to be alive as well.
-      //
-      for (unsigned op = 0, End = I->getNumOperands(); op != End; ++op)
-        if (Instruction *Operand = dyn_cast<Instruction>(I->getOperand(op)))
-          markInstructionLive(Operand);
-    }
+  // Propagate liveness backwards to operands.
+  while (!worklist.empty()) {
+    Instruction* curr = worklist.back();
+    worklist.pop_back();
+    
+    for (Instruction::op_iterator OI = curr->op_begin(), OE = curr->op_end();
+         OI != OE; ++OI)
+      if (Instruction* Inst = dyn_cast<Instruction>(OI))
+        if (alive.insert(Inst))
+          worklist.push_back(Inst);
   }
-
-  DEBUG(
-    DOUT << "Current Function: X = Live\n";
-    for (Function::iterator I = Func->begin(), E = Func->end(); I != E; ++I){
-      DOUT << I->getName() << ":\t"
-           << (AliveBlocks.count(I) ? "LIVE\n" : "DEAD\n");
-      for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE; ++BI){
-        if (LiveSet.count(BI)) DOUT << "X ";
-        DOUT << *BI;
-      }
-    });
-
-  // All blocks being live is a common case, handle it specially.
-  if (AliveBlocks.size() == Func->size()) {  // No dead blocks?
-    for (Function::iterator I = Func->begin(), E = Func->end(); I != E; ++I) {
-      // Loop over all of the instructions in the function deleting instructions
-      // to drop their references.
-      deleteDeadInstructionsInLiveBlock(I);
-
-      // Check to make sure the terminator instruction is live.  If it isn't,
-      // this means that the condition that it branches on (we know it is not an
-      // unconditional branch), is not needed to make the decision of where to
-      // go to, because all outgoing edges go to the same place.  We must remove
-      // the use of the condition (because it's probably dead), so we convert
-      // the terminator to an unconditional branch.
-      //
-      TerminatorInst *TI = I->getTerminator();
-      if (!LiveSet.count(TI))
-        convertToUnconditionalBranch(TI);
+  
+  // The inverse of the live set is the dead set.  These are those instructions
+  // which have no side effects and do not influence the control flow or return
+  // value of the function, and may therefore be deleted safely.
+  SmallPtrSet<Instruction*, 32> dead;
+  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
+    if (!alive.count(I.getInstructionIterator())) {
+      dead.insert(I.getInstructionIterator());
+      I->dropAllReferences();
     }
-
-    return MadeChanges;
-  }
-
-
-  // If the entry node is dead, insert a new entry node to eliminate the entry
-  // node as a special case.
-  //
-  if (!AliveBlocks.count(&Func->front())) {
-    BasicBlock *NewEntry = BasicBlock::Create();
-    BranchInst::Create(&Func->front(), NewEntry);
-    Func->getBasicBlockList().push_front(NewEntry);
-    AliveBlocks.insert(NewEntry);    // This block is always alive!
-    LiveSet.insert(NewEntry->getTerminator());  // The branch is live
+  
+  for (SmallPtrSet<Instruction*, 32>::iterator I = dead.begin(),
+       E = dead.end(); I != E; ++I) {
+    NumRemoved++;
+    (*I)->eraseFromParent();
   }
-
-  // Loop over all of the alive blocks in the function.  If any successor
-  // blocks are not alive, we adjust the outgoing branches to branch to the
-  // first live postdominator of the live block, adjusting any PHI nodes in
-  // the block to reflect this.
-  //
-  for (Function::iterator I = Func->begin(), E = Func->end(); I != E; ++I)
-    if (AliveBlocks.count(I)) {
-      BasicBlock *BB = I;
-      TerminatorInst *TI = BB->getTerminator();
-
-      // If the terminator instruction is alive, but the block it is contained
-      // in IS alive, this means that this terminator is a conditional branch on
-      // a condition that doesn't matter.  Make it an unconditional branch to
-      // ONE of the successors.  This has the side effect of dropping a use of
-      // the conditional value, which may also be dead.
-      if (!LiveSet.count(TI))
-        TI = convertToUnconditionalBranch(TI);
-
-      // Loop over all of the successors, looking for ones that are not alive.
-      // We cannot save the number of successors in the terminator instruction
-      // here because we may remove them if we don't have a postdominator.
-      //
-      for (unsigned i = 0; i != TI->getNumSuccessors(); ++i)
-        if (!AliveBlocks.count(TI->getSuccessor(i))) {
-          // Scan up the postdominator tree, looking for the first
-          // postdominator that is alive, and the last postdominator that is
-          // dead...
-          //
-          DomTreeNode *LastNode = DT[TI->getSuccessor(i)];
-          DomTreeNode *NextNode = 0;
-
-          if (LastNode) {
-            NextNode = LastNode->getIDom();
-            while (!AliveBlocks.count(NextNode->getBlock())) {
-              LastNode = NextNode;
-              NextNode = NextNode->getIDom();
-              if (NextNode == 0) {
-                LastNode = 0;
-                break;
-              }
-            }
-          }
-
-          // There is a special case here... if there IS no post-dominator for
-          // the block we have nowhere to point our branch to.  Instead, convert
-          // it to a return.  This can only happen if the code branched into an
-          // infinite loop.  Note that this may not be desirable, because we
-          // _are_ altering the behavior of the code.  This is a well known
-          // drawback of ADCE, so in the future if we choose to revisit the
-          // decision, this is where it should be.
-          //
-          if (LastNode == 0) {        // No postdominator!
-            if (!isa<InvokeInst>(TI)) {
-              // Call RemoveSuccessor to transmogrify the terminator instruction
-              // to not contain the outgoing branch, or to create a new
-              // terminator if the form fundamentally changes (i.e.,
-              // unconditional branch to return).  Note that this will change a
-              // branch into an infinite loop into a return instruction!
-              //
-              RemoveSuccessor(TI, i);
-
-              // RemoveSuccessor may replace TI... make sure we have a fresh
-              // pointer.
-              //
-              TI = BB->getTerminator();
-
-              // Rescan this successor...
-              --i;
-            } else {
-
-            }
-          } else {
-            // Get the basic blocks that we need...
-            BasicBlock *LastDead = LastNode->getBlock();
-            BasicBlock *NextAlive = NextNode->getBlock();
-
-            // Make the conditional branch now go to the next alive block...
-            TI->getSuccessor(i)->removePredecessor(BB);
-            TI->setSuccessor(i, NextAlive);
-
-            // If there are PHI nodes in NextAlive, we need to add entries to
-            // the PHI nodes for the new incoming edge.  The incoming values
-            // should be identical to the incoming values for LastDead.
-            //
-            for (BasicBlock::iterator II = NextAlive->begin();
-                 isa<PHINode>(II); ++II) {
-              PHINode *PN = cast<PHINode>(II);
-              if (LiveSet.count(PN)) {  // Only modify live phi nodes
-                // Get the incoming value for LastDead...
-                int OldIdx = PN->getBasicBlockIndex(LastDead);
-                assert(OldIdx != -1 &&"LastDead is not a pred of NextAlive!");
-                Value *InVal = PN->getIncomingValue(OldIdx);
-
-                // Add an incoming value for BB now...
-                PN->addIncoming(InVal, BB);
-              }
-            }
-          }
-        }
-
-      // Now loop over all of the instructions in the basic block, deleting
-      // dead instructions.  This is so that the next sweep over the program
-      // can safely delete dead instructions without other dead instructions
-      // still referring to them.
-      //
-      deleteDeadInstructionsInLiveBlock(BB);
-    }
-
-  // Loop over all of the basic blocks in the function, dropping references of
-  // the dead basic blocks.  We must do this after the previous step to avoid
-  // dropping references to PHIs which still have entries...
-  //
-  std::vector<BasicBlock*> DeadBlocks;
-  for (Function::iterator BB = Func->begin(), E = Func->end(); BB != E; ++BB)
-    if (!AliveBlocks.count(BB)) {
-      // Remove PHI node entries for this block in live successor blocks.
-      for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
-        if (!SI->empty() && isa<PHINode>(SI->front()) && AliveBlocks.count(*SI))
-          (*SI)->removePredecessor(BB);
-
-      BB->dropAllReferences();
-      MadeChanges = true;
-      DeadBlocks.push_back(BB);
-    }
-
-  NumBlockRemoved += DeadBlocks.size();
-
-  // Now loop through all of the blocks and delete the dead ones.  We can safely
-  // do this now because we know that there are no references to dead blocks
-  // (because they have dropped all of their references).
-  for (std::vector<BasicBlock*>::iterator I = DeadBlocks.begin(),
-         E = DeadBlocks.end(); I != E; ++I)
-    Func->getBasicBlockList().erase(*I);
-
-  return MadeChanges;
+    
+  return !dead.empty();
 }
+
+FunctionPass *llvm::createAggressiveDCEPass() {
+  return new ADCE();
+}
\ No newline at end of file
diff --git a/llvm/test/Transforms/ADCE/2003-12-19-MergeReturn.ll b/llvm/test/Transforms/ADCE/2003-12-19-MergeReturn.ll
deleted file mode 100644
index b2c294b1df0..00000000000
--- a/llvm/test/Transforms/ADCE/2003-12-19-MergeReturn.ll
+++ /dev/null
@@ -1,27 +0,0 @@
-; This testcase was failing because without merging the return blocks, ADCE
-; didn't know that it could get rid of the then.0 block.
-
-; RUN: llvm-as < %s | opt -adce | llvm-dis | not grep load
-
-
-define void @main(i32 %argc, i8** %argv) {
-entry:
-        call void @__main( )
-        %tmp.1 = icmp ule i32 %argc, 5          ; <i1> [#uses=1]
-        br i1 %tmp.1, label %then.0, label %return
-
-then.0:         ; preds = %entry
-        %tmp.8 = load i8** %argv                ; <i8*> [#uses=1]
-        %tmp.10 = load i8* %tmp.8               ; <i8> [#uses=1]
-        %tmp.11 = icmp eq i8 %tmp.10, 98                ; <i1> [#uses=1]
-        br i1 %tmp.11, label %then.1, label %return
-
-then.1:         ; preds = %then.0
-        ret void
-
-return:         ; preds = %then.0, %entry
-        ret void
-}
-
-declare void @__main()
-
diff --git a/llvm/test/Transforms/ADCE/dead-phi-edge.ll b/llvm/test/Transforms/ADCE/dead-phi-edge.ll
deleted file mode 100644
index 844560181a2..00000000000
--- a/llvm/test/Transforms/ADCE/dead-phi-edge.ll
+++ /dev/null
@@ -1,17 +0,0 @@
-; RUN: llvm-as < %s | opt -adce | llvm-dis | not grep call
-
-; The call is not live just because the PHI uses the call retval!
-
-define i32 @test(i32 %X) {
-; <label>:0
-        br label %Done
-
-DeadBlock:              ; No predecessors!
-        %Y = call i32 @test( i32 0 )            ; <i32> [#uses=1]
-        br label %Done
-
-Done:           ; preds = %DeadBlock, %0
-        %Z = phi i32 [ %X, %0 ], [ %Y, %DeadBlock ]             ; <i32> [#uses=1]
-        ret i32 %Z
-}
-