Fix a crash in scalarrepl for memcpy/memmove where the source and destination

are the same.  I had already fixed a similar problem where the source and
destination were different bitcasts derived from the same alloca, but the
previous fix still did not handle the case where both operands are exactly
the same value.  Radar 7552893.

llvm-svn: 93848

1 files changed, 10 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 9e1e79a1c29..336da509b48 100644
--- a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -752,9 +752,16 @@ void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
       }
       break;
     }
-    // If OtherPtr has already been rewritten, this intrinsic will be dead.
-    if (OtherPtr == NewElts[0])
+    // Copying the alloca to itself is a no-op: just delete it.
+    if (OtherPtr == AI || OtherPtr == NewElts[0]) {
+      // This code will run twice for a no-op memcpy -- once for each operand.
+      // Put only one reference to MI on the DeadInsts list.
+      for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
+             E = DeadInsts.end(); I != E; ++I)
+        if (*I == MI) return;
+      DeadInsts.push_back(MI);
       return;
+    }
     
     if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
       if (BCE->getOpcode() == Instruction::BitCast)
@@ -779,10 +786,7 @@ void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
     Value *OtherElt = 0;
     unsigned OtherEltAlign = MemAlignment;
     
-    if (OtherPtr == AI) {
-      OtherElt = NewElts[i];
-      OtherEltAlign = 0;
-    } else if (OtherPtr) {
+    if (OtherPtr) {
       Value *Idx[2] = { Zero,
                       ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
       OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,