Revert r188119 "Kill some duplicated code for removing unreachable BBs."

It is breaking builbots with libgmalloc enabled on Mac OS X.

$ cd llvm ; mkdir release ; cd release
$ ../configure --enable-optimized —prefix=$PWD/install
$ make
$ make check
$ Release+Asserts/bin/llvm-lit -v --param use_gmalloc=1 --param \
  gmalloc_path=/usr/lib/libgmalloc.dylib \
  ../test/Instrumentation/DataFlowSanitizer/args-unreachable-bb.ll

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188142 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 160 insertions, 5 deletions

diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index 8371f6d352..6d05640216 100644
--- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -66,6 +66,161 @@ FunctionPass *llvm::createCFGSimplificationPass() {
   return new CFGSimplifyPass();
 }
 
+/// changeToUnreachable - Insert an unreachable instruction before the specified
+/// instruction, making it and the rest of the code in the block dead.
+static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
+  BasicBlock *BB = I->getParent();
+  // Loop over all of the successors, removing BB's entry from any PHI
+  // nodes.
+  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+    (*SI)->removePredecessor(BB);
+
+  // Insert a call to llvm.trap right before this.  This turns the undefined
+  // behavior into a hard fail instead of falling through into random code.
+  if (UseLLVMTrap) {
+    Function *TrapFn =
+      Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
+    CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
+    CallTrap->setDebugLoc(I->getDebugLoc());
+  }
+  new UnreachableInst(I->getContext(), I);
+
+  // All instructions after this are dead.
+  BasicBlock::iterator BBI = I, BBE = BB->end();
+  while (BBI != BBE) {
+    if (!BBI->use_empty())
+      BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
+    BB->getInstList().erase(BBI++);
+  }
+}
+
+/// changeToCall - Convert the specified invoke into a normal call.
+static void changeToCall(InvokeInst *II) {
+  SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
+  CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
+  NewCall->takeName(II);
+  NewCall->setCallingConv(II->getCallingConv());
+  NewCall->setAttributes(II->getAttributes());
+  NewCall->setDebugLoc(II->getDebugLoc());
+  II->replaceAllUsesWith(NewCall);
+
+  // Follow the call by a branch to the normal destination.
+  BranchInst::Create(II->getNormalDest(), II);
+
+  // Update PHI nodes in the unwind destination
+  II->getUnwindDest()->removePredecessor(II->getParent());
+  II->eraseFromParent();
+}
+
+static bool markAliveBlocks(BasicBlock *BB,
+                            SmallPtrSet<BasicBlock*, 128> &Reachable) {
+
+  SmallVector<BasicBlock*, 128> Worklist;
+  Worklist.push_back(BB);
+  Reachable.insert(BB);
+  bool Changed = false;
+  do {
+    BB = Worklist.pop_back_val();
+
+    // Do a quick scan of the basic block, turning any obviously unreachable
+    // instructions into LLVM unreachable insts.  The instruction combining pass
+    // canonicalizes unreachable insts into stores to null or undef.
+    for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
+      if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
+        if (CI->doesNotReturn()) {
+          // If we found a call to a no-return function, insert an unreachable
+          // instruction after it.  Make sure there isn't *already* one there
+          // though.
+          ++BBI;
+          if (!isa<UnreachableInst>(BBI)) {
+            // Don't insert a call to llvm.trap right before the unreachable.
+            changeToUnreachable(BBI, false);
+            Changed = true;
+          }
+          break;
+        }
+      }
+
+      // Store to undef and store to null are undefined and used to signal that
+      // they should be changed to unreachable by passes that can't modify the
+      // CFG.
+      if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
+        // Don't touch volatile stores.
+        if (SI->isVolatile()) continue;
+
+        Value *Ptr = SI->getOperand(1);
+
+        if (isa<UndefValue>(Ptr) ||
+            (isa<ConstantPointerNull>(Ptr) &&
+             SI->getPointerAddressSpace() == 0)) {
+          changeToUnreachable(SI, true);
+          Changed = true;
+          break;
+        }
+      }
+    }
+
+    // Turn invokes that call 'nounwind' functions into ordinary calls.
+    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+      Value *Callee = II->getCalledValue();
+      if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
+        changeToUnreachable(II, true);
+        Changed = true;
+      } else if (II->doesNotThrow()) {
+        if (II->use_empty() && II->onlyReadsMemory()) {
+          // jump to the normal destination branch.
+          BranchInst::Create(II->getNormalDest(), II);
+          II->getUnwindDest()->removePredecessor(II->getParent());
+          II->eraseFromParent();
+        } else
+          changeToCall(II);
+        Changed = true;
+      }
+    }
+
+    Changed |= ConstantFoldTerminator(BB, true);
+    for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+      if (Reachable.insert(*SI))
+        Worklist.push_back(*SI);
+  } while (!Worklist.empty());
+  return Changed;
+}
+
+/// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
+/// if they are in a dead cycle.  Return true if a change was made, false
+/// otherwise.
+static bool removeUnreachableBlocksFromFn(Function &F) {
+  SmallPtrSet<BasicBlock*, 128> Reachable;
+  bool Changed = markAliveBlocks(F.begin(), Reachable);
+
+  // If there are unreachable blocks in the CFG...
+  if (Reachable.size() == F.size())
+    return Changed;
+
+  assert(Reachable.size() < F.size());
+  NumSimpl += F.size()-Reachable.size();
+
+  // Loop over all of the basic blocks that are not reachable, dropping all of
+  // their internal references...
+  for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
+    if (Reachable.count(BB))
+      continue;
+
+    for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+      if (Reachable.count(*SI))
+        (*SI)->removePredecessor(BB);
+    BB->dropAllReferences();
+  }
+
+  for (Function::iterator I = ++F.begin(); I != F.end();)
+    if (!Reachable.count(I))
+      I = F.getBasicBlockList().erase(I);
+    else
+      ++I;
+
+  return true;
+}
+
 /// mergeEmptyReturnBlocks - If we have more than one empty (other than phi
 /// node) return blocks, merge them together to promote recursive block merging.
 static bool mergeEmptyReturnBlocks(Function &F) {
@@ -170,7 +325,7 @@ static bool iterativelySimplifyCFG(Function &F, const TargetTransformInfo &TTI,
 bool CFGSimplifyPass::runOnFunction(Function &F) {
   const TargetTransformInfo &TTI = getAnalysis<TargetTransformInfo>();
   const DataLayout *TD = getAnalysisIfAvailable<DataLayout>();
-  bool EverChanged = removeUnreachableBlocks(F);
+  bool EverChanged = removeUnreachableBlocksFromFn(F);
   EverChanged |= mergeEmptyReturnBlocks(F);
   EverChanged |= iterativelySimplifyCFG(F, TTI, TD);
 
@@ -178,16 +333,16 @@ bool CFGSimplifyPass::runOnFunction(Function &F) {
   if (!EverChanged) return false;
 
   // iterativelySimplifyCFG can (rarely) make some loops dead.  If this happens,
-  // removeUnreachableBlocks is needed to nuke them, which means we should
+  // removeUnreachableBlocksFromFn is needed to nuke them, which means we should
   // iterate between the two optimizations.  We structure the code like this to
   // avoid reruning iterativelySimplifyCFG if the second pass of
-  // removeUnreachableBlocks doesn't do anything.
-  if (!removeUnreachableBlocks(F))
+  // removeUnreachableBlocksFromFn doesn't do anything.
+  if (!removeUnreachableBlocksFromFn(F))
     return true;
 
   do {
     EverChanged = iterativelySimplifyCFG(F, TTI, TD);
-    EverChanged |= removeUnreachableBlocks(F);
+    EverChanged |= removeUnreachableBlocksFromFn(F);
   } while (EverChanged);
 
   return true;