1 files changed, 82 insertions, 44 deletions

diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 1ff4329c84..301ee2f663 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -30,6 +30,7 @@
 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/ADT/SetVector.h"
@@ -45,6 +46,7 @@ namespace {
     AliasAnalysis *AA;
     MemoryDependenceAnalysis *MD;
     DominatorTree *DT;
+    const TargetLibraryInfo *TLI;
 
     static char ID; // Pass identification, replacement for typeid
     DSE() : FunctionPass(ID), AA(0), MD(0), DT(0) {
@@ -55,6 +57,7 @@ namespace {
       AA = &getAnalysis<AliasAnalysis>();
       MD = &getAnalysis<MemoryDependenceAnalysis>();
       DT = &getAnalysis<DominatorTree>();
+      TLI = AA->getTargetLibraryInfo();
 
       bool Changed = false;
       for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
@@ -144,7 +147,7 @@ static void DeleteDeadInstruction(Instruction *I,
 
 /// hasMemoryWrite - Does this instruction write some memory?  This only returns
 /// true for things that we can analyze with other helpers below.
-static bool hasMemoryWrite(Instruction *I) {
+static bool hasMemoryWrite(Instruction *I, const TargetLibraryInfo *TLI) {
   if (isa<StoreInst>(I))
     return true;
   if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
@@ -159,6 +162,26 @@ static bool hasMemoryWrite(Instruction *I) {
       return true;
     }
   }
+  if (CallSite CS = I) {
+    if (Function *F = CS.getCalledFunction()) {
+      if (TLI && TLI->has(LibFunc::strcpy) &&
+          F->getName() == TLI->getName(LibFunc::strcpy)) {
+        return true;
+      }
+      if (TLI && TLI->has(LibFunc::strncpy) &&
+          F->getName() == TLI->getName(LibFunc::strncpy)) {
+        return true;
+      }
+      if (TLI && TLI->has(LibFunc::strcat) &&
+          F->getName() == TLI->getName(LibFunc::strcat)) {
+        return true;
+      }
+      if (TLI && TLI->has(LibFunc::strncat) &&
+          F->getName() == TLI->getName(LibFunc::strncat)) {
+        return true;
+      }
+    }
+  }
   return false;
 }
 
@@ -206,7 +229,8 @@ getLocForWrite(Instruction *Inst, AliasAnalysis &AA) {
 /// instruction if any.
 static AliasAnalysis::Location
 getLocForRead(Instruction *Inst, AliasAnalysis &AA) {
-  assert(hasMemoryWrite(Inst) && "Unknown instruction case");
+  assert(hasMemoryWrite(Inst, AA.getTargetLibraryInfo()) &&
+         "Unknown instruction case");
 
   // The only instructions that both read and write are the mem transfer
   // instructions (memcpy/memmove).
@@ -223,23 +247,29 @@ static bool isRemovable(Instruction *I) {
   if (StoreInst *SI = dyn_cast<StoreInst>(I))
     return SI->isUnordered();
 
-  IntrinsicInst *II = cast<IntrinsicInst>(I);
-  switch (II->getIntrinsicID()) {
-  default: llvm_unreachable("doesn't pass 'hasMemoryWrite' predicate");
-  case Intrinsic::lifetime_end:
-    // Never remove dead lifetime_end's, e.g. because it is followed by a
-    // free.
-    return false;
-  case Intrinsic::init_trampoline:
-    // Always safe to remove init_trampoline.
-    return true;
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+    switch (II->getIntrinsicID()) {
+    default: llvm_unreachable("doesn't pass 'hasMemoryWrite' predicate");
+    case Intrinsic::lifetime_end:
+      // Never remove dead lifetime_end's, e.g. because it is followed by a
+      // free.
+      return false;
+    case Intrinsic::init_trampoline:
+      // Always safe to remove init_trampoline.
+      return true;
 
-  case Intrinsic::memset:
-  case Intrinsic::memmove:
-  case Intrinsic::memcpy:
-    // Don't remove volatile memory intrinsics.
-    return !cast<MemIntrinsic>(II)->isVolatile();
+    case Intrinsic::memset:
+    case Intrinsic::memmove:
+    case Intrinsic::memcpy:
+      // Don't remove volatile memory intrinsics.
+      return !cast<MemIntrinsic>(II)->isVolatile();
+    }
   }
+
+  if (CallSite CS = I)
+    return CS.getInstruction()->use_empty();
+
+  return false;
 }
 
 
@@ -250,14 +280,19 @@ static bool isShortenable(Instruction *I) {
   if (isa<StoreInst>(I))
     return false;
 
-  IntrinsicInst *II = cast<IntrinsicInst>(I);
-  switch (II->getIntrinsicID()) {
-    default: return false;
-    case Intrinsic::memset:
-    case Intrinsic::memcpy:
-      // Do shorten memory intrinsics.
-      return true;
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+    switch (II->getIntrinsicID()) {
+      default: return false;
+      case Intrinsic::memset:
+      case Intrinsic::memcpy:
+        // Do shorten memory intrinsics.
+        return true;
+    }
   }
+
+  // Don't shorten libcalls calls for now.
+
+  return false;
 }
 
 /// getStoredPointerOperand - Return the pointer that is being written to.
@@ -267,12 +302,18 @@ static Value *getStoredPointerOperand(Instruction *I) {
   if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I))
     return MI->getDest();
 
-  IntrinsicInst *II = cast<IntrinsicInst>(I);
-  switch (II->getIntrinsicID()) {
-  default: llvm_unreachable("Unexpected intrinsic!");
-  case Intrinsic::init_trampoline:
-    return II->getArgOperand(0);
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+    switch (II->getIntrinsicID()) {
+    default: llvm_unreachable("Unexpected intrinsic!");
+    case Intrinsic::init_trampoline:
+      return II->getArgOperand(0);
+    }
   }
+
+  CallSite CS = I;
+  // All the supported functions so far happen to have dest as their first
+  // argument.
+  return CS.getArgument(0);
 }
 
 static uint64_t getPointerSize(const Value *V, AliasAnalysis &AA) {
@@ -455,13 +496,13 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
     Instruction *Inst = BBI++;
 
     // Handle 'free' calls specially.
-    if (CallInst *F = isFreeCall(Inst, AA->getTargetLibraryInfo())) {
+    if (CallInst *F = isFreeCall(Inst, TLI)) {
       MadeChange |= HandleFree(F);
       continue;
     }
 
     // If we find something that writes memory, get its memory dependence.
-    if (!hasMemoryWrite(Inst))
+    if (!hasMemoryWrite(Inst, TLI))
       continue;
 
     MemDepResult InstDep = MD->getDependency(Inst);
@@ -484,7 +525,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
           // in case we need it.
           WeakVH NextInst(BBI);
 
-          DeleteDeadInstruction(SI, *MD, AA->getTargetLibraryInfo());
+          DeleteDeadInstruction(SI, *MD, TLI);
 
           if (NextInst == 0)  // Next instruction deleted.
             BBI = BB.begin();
@@ -531,7 +572,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
                 << *DepWrite << "\n  KILLER: " << *Inst << '\n');
 
           // Delete the store and now-dead instructions that feed it.
-          DeleteDeadInstruction(DepWrite, *MD, AA->getTargetLibraryInfo());
+          DeleteDeadInstruction(DepWrite, *MD, TLI);
           ++NumFastStores;
           MadeChange = true;
 
@@ -628,7 +669,7 @@ bool DSE::HandleFree(CallInst *F) {
     MemDepResult Dep = MD->getPointerDependencyFrom(Loc, false, InstPt, BB);
     while (Dep.isDef() || Dep.isClobber()) {
       Instruction *Dependency = Dep.getInst();
-      if (!hasMemoryWrite(Dependency) || !isRemovable(Dependency))
+      if (!hasMemoryWrite(Dependency, TLI) || !isRemovable(Dependency))
         break;
 
       Value *DepPointer =
@@ -641,7 +682,7 @@ bool DSE::HandleFree(CallInst *F) {
       Instruction *Next = llvm::next(BasicBlock::iterator(Dependency));
 
       // DCE instructions only used to calculate that store
-      DeleteDeadInstruction(Dependency, *MD, AA->getTargetLibraryInfo());
+      DeleteDeadInstruction(Dependency, *MD, TLI);
       ++NumFastStores;
       MadeChange = true;
 
@@ -681,8 +722,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
 
     // Okay, so these are dead heap objects, but if the pointer never escapes
     // then it's leaked by this function anyways.
-    else if (isAllocLikeFn(I, AA->getTargetLibraryInfo()) &&
-             !PointerMayBeCaptured(I, true, true))
+    else if (isAllocLikeFn(I, TLI) && !PointerMayBeCaptured(I, true, true))
       DeadStackObjects.insert(I);
   }
 
@@ -698,7 +738,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
     --BBI;
 
     // If we find a store, check to see if it points into a dead stack value.
-    if (hasMemoryWrite(BBI) && isRemovable(BBI)) {
+    if (hasMemoryWrite(BBI, TLI) && isRemovable(BBI)) {
       // See through pointer-to-pointer bitcasts
       SmallVector<Value *, 4> Pointers;
       GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers);
@@ -726,8 +766,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
               dbgs() << '\n');
 
         // DCE instructions only used to calculate that store.
-        DeleteDeadInstruction(Dead, *MD, AA->getTargetLibraryInfo(),
-                              &DeadStackObjects);
+        DeleteDeadInstruction(Dead, *MD, TLI, &DeadStackObjects);
         ++NumFastStores;
         MadeChange = true;
         continue;
@@ -735,10 +774,9 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
     }
 
     // Remove any dead non-memory-mutating instructions.
-    if (isInstructionTriviallyDead(BBI, AA->getTargetLibraryInfo())) {
+    if (isInstructionTriviallyDead(BBI, TLI)) {
       Instruction *Inst = BBI++;
-      DeleteDeadInstruction(Inst, *MD, AA->getTargetLibraryInfo(),
-                            &DeadStackObjects);
+      DeleteDeadInstruction(Inst, *MD, TLI, &DeadStackObjects);
       ++NumFastOther;
       MadeChange = true;
       continue;
@@ -754,7 +792,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
     if (CallSite CS = cast<Value>(BBI)) {
       // Remove allocation function calls from the list of dead stack objects; 
       // there can't be any references before the definition.
-      if (isAllocLikeFn(BBI, AA->getTargetLibraryInfo()))
+      if (isAllocLikeFn(BBI, TLI))
         DeadStackObjects.remove(BBI);
 
       // If this call does not access memory, it can't be loading any of our