From a756b1d914eaf4ad610d29398e5831b394bd1547 Mon Sep 17 00:00:00 2001
From: Bob Wilson <bob.wilson@apple.com>
Date: Tue, 19 Jan 2010 04:32:48 +0000
Subject: [PATCH] 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93848 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/ScalarReplAggregates.cpp    | 16 ++++++++++------
 test/Transforms/ScalarRepl/2010-01-18-SelfCopy.ll | 18 ++++++++++++++++++
 2 files changed, 28 insertions(+), 6 deletions(-)
 create mode 100644 test/Transforms/ScalarRepl/2010-01-18-SelfCopy.ll

diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 9e1e79a1c29..336da509b48 100644
--- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/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,
diff --git a/test/Transforms/ScalarRepl/2010-01-18-SelfCopy.ll b/test/Transforms/ScalarRepl/2010-01-18-SelfCopy.ll
new file mode 100644
index 00000000000..74cf251503c
--- /dev/null
+++ b/test/Transforms/ScalarRepl/2010-01-18-SelfCopy.ll
@@ -0,0 +1,18 @@
+; RUN: opt < %s -scalarrepl -S | FileCheck %s
+; Radar 7552893
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
+
+%struct.test = type { [3 x double ] }
+
+define arm_apcscc void @test_memcpy_self() nounwind {
+; CHECK: @test_memcpy_self
+; CHECK-NOT: alloca
+; CHECK: ret void
+  %1 = alloca %struct.test
+  %2 = bitcast %struct.test* %1 to i8*
+  call void @llvm.memcpy.i32(i8* %2, i8* %2, i32 24, i32 4)
+  ret void
+}
+
+declare void @llvm.memcpy.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind
-- 
2.11.0