When removing a store to an alloca that has only one

use, check also for the case where it has two uses,
the other being a llvm.dbg.declare.  This is needed so
debug info doesn't affect codegen.

llvm-svn: 65970

2 files changed, 49 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index ad94aaa0593..64dd1031db9 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -250,6 +250,8 @@ namespace {
     Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
                                    bool DoXform = true);
     bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
+    DbgDeclareInst *hasOneUsePlusDeclare(Value *V);
+
 
   public:
     // InsertNewInstBefore - insert an instruction New before instruction Old
@@ -11403,6 +11405,23 @@ static bool equivalentAddressValues(Value *A, Value *B) {
   return false;
 }
 
+// If this instruction has two uses, one of which is a llvm.dbg.declare,
+// return the llvm.dbg.declare.
+DbgDeclareInst *InstCombiner::hasOneUsePlusDeclare(Value *V) {
+  if (!V->hasNUses(2))
+    return 0;
+  for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
+       UI != E; ++UI) {
+    if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(UI))
+      return DI;
+    if (isa<BitCastInst>(UI) && UI->hasOneUse()) {
+      if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(UI->use_begin()))
+        return DI;
+      }
+  }
+  return 0;
+}
+
 Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
   Value *Val = SI.getOperand(0);
   Value *Ptr = SI.getOperand(1);
@@ -11415,20 +11434,39 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
   
   // If the RHS is an alloca with a single use, zapify the store, making the
   // alloca dead.
-  if (Ptr->hasOneUse() && !SI.isVolatile()) {
-    if (isa<AllocaInst>(Ptr)) {
-      EraseInstFromFunction(SI);
-      ++NumCombined;
-      return 0;
-    }
-    
-    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr))
-      if (isa<AllocaInst>(GEP->getOperand(0)) &&
-          GEP->getOperand(0)->hasOneUse()) {
+  // If the RHS is an alloca with a two uses, the other one being a 
+  // llvm.dbg.declare, zapify the store and the declare, making the
+  // alloca dead.  We must do this to prevent declare's from affecting
+  // codegen.
+  if (!SI.isVolatile()) {
+    if (Ptr->hasOneUse()) {
+      if (isa<AllocaInst>(Ptr)) {
         EraseInstFromFunction(SI);
         ++NumCombined;
         return 0;
       }
+      if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
+        if (isa<AllocaInst>(GEP->getOperand(0))) {
+          if (GEP->getOperand(0)->hasOneUse()) {
+            EraseInstFromFunction(SI);
+            ++NumCombined;
+            return 0;
+          }
+          if (DbgDeclareInst *DI = hasOneUsePlusDeclare(GEP->getOperand(0))) {
+            EraseInstFromFunction(*DI);
+            EraseInstFromFunction(SI);
+            ++NumCombined;
+            return 0;
+          }
+        }
+      }
+    }
+    if (DbgDeclareInst *DI = hasOneUsePlusDeclare(Ptr)) {
+      EraseInstFromFunction(*DI);
+      EraseInstFromFunction(SI);
+      ++NumCombined;
+      return 0;
+    }
   }
 
   // Attempt to improve the alignment.
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 5f9a8b5c421..2887bdc46b5 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -540,8 +540,7 @@ void llvm::CopyPrecedingStopPoint(Instruction *I,
   if (I != I->getParent()->begin()) {
     BasicBlock::iterator BBI = I;  --BBI;
     if (DbgStopPointInst *DSPI = dyn_cast<DbgStopPointInst>(BBI)) {
-      DbgStopPointInst *newDSPI =
-        reinterpret_cast<DbgStopPointInst*>(DSPI->clone());
+      CallInst *newDSPI = DSPI->clone();
       newDSPI->insertBefore(InsertPos);
     }
   }