Index: lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -698,6 +698,29 @@
           return true;
         }
       }
+
+      if (AllocaInst *AI = dyn_cast<AllocaInst>(
+              LI->getPointerOperand()->stripPointerCasts())) {
+        if (Argument *Arg = dyn_cast<Argument>(
+                SI->getPointerOperand()->stripPointerCasts())) {
+          if (Arg->hasStructRetAttr() && Arg->hasNoAliasAttr() &&
+              Arg->getType() == AI->getType()) {
+            AI->replaceAllUsesWith(Arg);
+
+            MD->removeInstruction(SI);
+            SI->eraseFromParent();
+
+            MD->removeInstruction(LI);
+            LI->eraseFromParent();
+
+            MD->removeInstruction(AI);
+            AI->eraseFromParent();
+
+            ++NumMemCpyInstr;
+            return true;
+          }
+        }
+      }
     }
   }
 
@@ -1177,6 +1200,8 @@
   //      lifetime copies undefined data, and we can therefore eliminate the
   //      memcpy in favor of the data that was already at the destination.
   //   d) memcpy from a just-memset'd source can be turned into memset.
+  //   e) memcpy from an alloca to a noalias sret can be converted into direct
+  //      access to the sret.
   if (DepInfo.isClobber()) {
     if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
       if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
@@ -1226,6 +1251,24 @@
         return true;
       }
 
+  if (AllocaInst *AI = dyn_cast<AllocaInst>(M->getSource())) {
+    if (Argument *Arg = dyn_cast<Argument>(M->getDest())) {
+      if (Arg->hasStructRetAttr() && Arg->hasNoAliasAttr() &&
+          Arg->getType() == AI->getType()) {
+        AI->replaceAllUsesWith(Arg);
+
+        MD->removeInstruction(M);
+        M->eraseFromParent();
+
+        MD->removeInstruction(AI);
+        AI->eraseFromParent();
+
+        ++NumMemCpyInstr;
+        return true;
+      }
+    }
+  }
+
   return false;
 }
 
Index: test/Transforms/MemCpyOpt/memcpy.ll
===================================================================
--- test/Transforms/MemCpyOpt/memcpy.ll
+++ test/Transforms/MemCpyOpt/memcpy.ll
@@ -202,6 +202,53 @@
   ret void
 }
 
+define void @elide_memcpy_to_noalias_sret(%struct.big* noalias nocapture sret,
+                                          %struct.big* nocapture readonly,
+                                          %struct.big* nocapture readonly) {
+; CHECK-LABEL: @elide_memcpy_to_noalias_sret
+; CHECK-NOT: memcpy
+  %4 = alloca %struct.big, align 4
+  %5 = bitcast %struct.big* %4 to i8*
+  call void @llvm.lifetime.start(i64 200, i8* %5)
+  br label %8
+
+; <label>:6:                                      ; preds = %8
+  %7 = bitcast %struct.big* %0 to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %7, i8* nonnull %5, i64 200, i32 4, i1 false)
+  call void @llvm.lifetime.end(i64 200, i8* nonnull %5)
+  ret void
+
+; <label>:8:                                      ; preds = %8, %3
+  %9 = phi i64 [ 0, %3 ], [ %16, %8 ]
+  %10 = getelementptr inbounds %struct.big, %struct.big* %1, i64 0, i32 0, i64 %9
+  %11 = load i32, i32* %10, align 4
+  %12 = getelementptr inbounds %struct.big, %struct.big* %2, i64 0, i32 0, i64 %9
+  %13 = load i32, i32* %12, align 4
+  %14 = xor i32 %13, %11
+  %15 = getelementptr inbounds %struct.big, %struct.big* %4, i64 0, i32 0, i64 %9
+  store i32 %14, i32* %15, align 4
+  %16 = add nuw nsw i64 %9, 1
+  %17 = icmp eq i64 %16, 50
+  br i1 %17, label %6, label %8
+}
+
+define void @pr2218(i8* noalias sret %result) {
+; CHECK-LABEL: @pr2218
+; CHECK: call void @initialize(i8* noalias sret %result)
+; CHECK: ret void
+entry:
+  %temporary = alloca i8          ; <i8*> [#uses=3]
+  %pointless = alloca i8          ; <i8*> [#uses=1]
+  call void @initialize(i8* noalias sret %temporary)
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %pointless, i8* %temporary, i64 1, i32 4, i1 false)
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %result, i8* %temporary, i64 1, i32 4, i1 false)
+  ret void
+}
+
+declare void @initialize(i8* noalias sret)
+declare void @llvm.lifetime.start(i64, i8* nocapture)
+declare void @llvm.lifetime.end(i64, i8* nocapture)
+
 declare void @f1(%struct.big* nocapture sret)
 declare void @f2(%struct.big*)