Fix a DAG combine bug visitBRCOND() is transforming br(xor(x, y)) to br(x != y).

It cahced XOR's operands before calling visitXOR() but failed to update the
operands when visitXOR changed the XOR node.

rdar://12968664


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171999 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 59 insertions, 12 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ff00d0d..359c4cf 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6735,18 +6735,24 @@ SDValue DAGCombiner::visitBRCOND(SDNode *N) {
     if (Op0.getOpcode() == Op1.getOpcode()) {
       // Avoid missing important xor optimizations.
       SDValue Tmp = visitXOR(TheXor);
-      if (Tmp.getNode() && Tmp.getNode() != TheXor) {
-        DEBUG(dbgs() << "\nReplacing.8 ";
-              TheXor->dump(&DAG);
-              dbgs() << "\nWith: ";
-              Tmp.getNode()->dump(&DAG);
-              dbgs() << '\n');
-        WorkListRemover DeadNodes(*this);
-        DAG.ReplaceAllUsesOfValueWith(N1, Tmp);
-        removeFromWorkList(TheXor);
-        DAG.DeleteNode(TheXor);
-        return DAG.getNode(ISD::BRCOND, N->getDebugLoc(),
-                           MVT::Other, Chain, Tmp, N2);
+      if (Tmp.getNode()) {
+        if (Tmp.getNode() != TheXor) {
+          DEBUG(dbgs() << "\nReplacing.8 ";
+                TheXor->dump(&DAG);
+                dbgs() << "\nWith: ";
+                Tmp.getNode()->dump(&DAG);
+                dbgs() << '\n');
+          WorkListRemover DeadNodes(*this);
+          DAG.ReplaceAllUsesOfValueWith(N1, Tmp);
+          removeFromWorkList(TheXor);
+          DAG.DeleteNode(TheXor);
+          return DAG.getNode(ISD::BRCOND, N->getDebugLoc(),
+                             MVT::Other, Chain, Tmp, N2);
+        }
+
+        // visitXOR has changed XOR's operands.
+        Op0 = TheXor->getOperand(0);
+        Op1 = TheXor->getOperand(1);
       }
     }
 
diff --git a/test/CodeGen/X86/2013-01-09-DAGCombineBug.ll b/test/CodeGen/X86/2013-01-09-DAGCombineBug.ll
new file mode 100644
index 0000000..db7ec8a
--- /dev/null
+++ b/test/CodeGen/X86/2013-01-09-DAGCombineBug.ll
@@ -0,0 +1,41 @@
+; RUN: llc -mtriple=x86_64-apple-macosx10.5.0 < %s
+
+; rdar://12968664
+
+define void @t() nounwind uwtable ssp {
+  br label %4
+
+; <label>:1                                       ; preds = %4, %2
+  ret void
+
+; <label>:2                                       ; preds = %6, %5, %3, %2
+  switch i32 undef, label %2 [
+    i32 1090573978, label %1
+    i32 1090573938, label %3
+    i32 1090573957, label %5
+  ]
+
+; <label>:3                                       ; preds = %4, %2
+  br i1 undef, label %2, label %4
+
+; <label>:4                                       ; preds = %6, %5, %3, %0
+  switch i32 undef, label %11 [
+    i32 1090573938, label %3
+    i32 1090573957, label %5
+    i32 1090573978, label %1
+    i32 165205179, label %6
+  ]
+
+; <label>:5                                       ; preds = %4, %2
+  br i1 undef, label %2, label %4
+
+; <label>:6                                       ; preds = %4
+  %7 = icmp eq i32 undef, 590901838
+  %8 = or i1 false, %7
+  %9 = or i1 true, %8
+  %10 = xor i1 %8, %9
+  br i1 %10, label %4, label %2
+
+; <label>:11                                      ; preds = %11, %4
+  br label %11
+}