X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FSimplifyCFGPass.cpp;h=bdcf9887b7c8ba50828fadc1aecb0e9aa47d2047;hb=06cb8ed00696eb14d1b831921452e50ec0568ea2;hp=738c5e8d13d1dd41ab9de95209855b15a6d8d89c;hpb=1cde4af15712f6ccdb81ab540df800cda90d0d74;p=oota-llvm.git

diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index 738c5e8d13d..bdcf9887b7c 100644
--- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -42,14 +42,17 @@ STATISTIC(NumSimpl, "Number of blocks simplified");
 namespace {
   struct CFGSimplifyPass : public FunctionPass {
     static char ID; // Pass identification, replacement for typeid
-    CFGSimplifyPass() : FunctionPass(&ID) {}
+    CFGSimplifyPass() : FunctionPass(ID) {
+      initializeCFGSimplifyPassPass(*PassRegistry::getPassRegistry());
+    }
 
     virtual bool runOnFunction(Function &F);
   };
 }
 
 char CFGSimplifyPass::ID = 0;
-static RegisterPass<CFGSimplifyPass> X("simplifycfg", "Simplify the CFG");
+INITIALIZE_PASS(CFGSimplifyPass, "simplifycfg",
+                "Simplify the CFG", false, false)
 
 // Public interface to the CFGSimplification pass
 FunctionPass *llvm::createCFGSimplificationPass() {
@@ -58,13 +61,21 @@ FunctionPass *llvm::createCFGSimplificationPass() {
 
 /// 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) {
+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.
@@ -78,21 +89,17 @@ static void ChangeToUnreachable(Instruction *I) {
 
 /// ChangeToCall - Convert the specified invoke into a normal call.
 static void ChangeToCall(InvokeInst *II) {
-  BasicBlock *BB = II->getParent();
-  SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
-  CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args.begin(),
-                                       Args.end(), "", 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(BB);
-  BB->getInstList().erase(II);
+  II->eraseFromParent();
 }
 
 static bool MarkAliveBlocks(BasicBlock *BB,
@@ -118,7 +125,8 @@ static bool MarkAliveBlocks(BasicBlock *BB,
           // though.
           ++BBI;
           if (!isa<UnreachableInst>(BBI)) {
-            ChangeToUnreachable(BBI);
+            // Don't insert a call to llvm.trap right before the unreachable.
+            ChangeToUnreachable(BBI, false);
             Changed = true;
           }
           break;
@@ -129,12 +137,15 @@ static bool MarkAliveBlocks(BasicBlock *BB,
       // 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);
+          ChangeToUnreachable(SI, true);
           Changed = true;
           break;
         }
@@ -142,13 +153,23 @@ static bool MarkAliveBlocks(BasicBlock *BB,
     }
 
     // Turn invokes that call 'nounwind' functions into ordinary calls.
-    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
-      if (II->doesNotThrow()) {
-        ChangeToCall(II);
+    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->eraseFromParent();
+        } else
+          ChangeToCall(II);
         Changed = true;
       }
+    }
 
-    Changed |= ConstantFoldTerminator(BB);
+    Changed |= ConstantFoldTerminator(BB, true);
     for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
       Worklist.push_back(*SI);
   } while (!Worklist.empty());
@@ -245,11 +266,12 @@ static bool MergeEmptyReturnBlocks(Function &F) {
     PHINode *RetBlockPHI = dyn_cast<PHINode>(RetBlock->begin());
     if (RetBlockPHI == 0) {
       Value *InVal = cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0);
-      RetBlockPHI = PHINode::Create(Ret->getOperand(0)->getType(), "merge",
+      pred_iterator PB = pred_begin(RetBlock), PE = pred_end(RetBlock);
+      RetBlockPHI = PHINode::Create(Ret->getOperand(0)->getType(),
+                                    std::distance(PB, PE), "merge",
                                     &RetBlock->front());
       
-      for (pred_iterator PI = pred_begin(RetBlock), E = pred_end(RetBlock);
-           PI != E; ++PI)
+      for (pred_iterator PI = PB; PI != PE; ++PI)
         RetBlockPHI->addIncoming(InVal, *PI);
       RetBlock->getTerminator()->setOperand(0, RetBlockPHI);
     }
@@ -273,10 +295,9 @@ static bool IterativeSimplifyCFG(Function &F, const TargetData *TD) {
   while (LocalChange) {
     LocalChange = false;
     
-    // Loop over all of the basic blocks (except the first one) and remove them
-    // if they are unneeded...
+    // Loop over all of the basic blocks and remove them if they are unneeded...
     //
-    for (Function::iterator BBIt = ++F.begin(); BBIt != F.end(); ) {
+    for (Function::iterator BBIt = F.begin(); BBIt != F.end(); ) {
       if (SimplifyCFG(BBIt++, TD)) {
         LocalChange = true;
         ++NumSimpl;