Revert "[DSE] Enable removal of lifetime intrinsics in terminating blocks"

llvm-svn: 245543

1 files changed, 3 insertions, 30 deletions

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index d64c5d24fc8..c8b0ea8c992 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -788,33 +788,15 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
 
   const DataLayout &DL = BB.getModule()->getDataLayout();
 
-  // becomes false once lifetime intrinsics are observable or useful for stack
-  // coloring
-  bool canRemoveLifetimeIntrinsics = true;
-
   // Scan the basic block backwards
   for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
     --BBI;
 
-    Value *V = nullptr;
-    if (canRemoveLifetimeIntrinsics)
-      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
-        switch (II->getIntrinsicID()) {
-          default: break;
-          case Intrinsic::lifetime_start:
-          case Intrinsic::lifetime_end:
-            V = II->getArgOperand(1);
-            break;
-        }
-
-    if (!V && hasMemoryWrite(BBI, *TLI) && isRemovable(BBI))
-      V = getStoredPointerOperand(BBI);
-
-    // If we found a store, check to see if it points into a dead stack value.
-    if (V) {
+    // If we find a store, check to see if it points into a dead stack value.
+    if (hasMemoryWrite(BBI, *TLI) && isRemovable(BBI)) {
       // See through pointer-to-pointer bitcasts
       SmallVector<Value *, 4> Pointers;
-      GetUnderlyingObjects(V, Pointers, DL);
+      GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers, DL);
 
       // Stores to stack values are valid candidates for removal.
       bool AllDead = true;
@@ -862,15 +844,6 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
       continue;
     }
 
-    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
-      if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
-        // We found a lifetime start for a live object, which we could not
-        // remove. So we must stop removing lifetime intrinsics from this block
-        // because they're useful for stack coloring again
-        canRemoveLifetimeIntrinsics = false;
-        continue;
-      }
-
     if (auto CS = CallSite(BBI)) {
       // Remove allocation function calls from the list of dead stack objects; 
       // there can't be any references before the definition.