Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -2413,7 +2413,7 @@
     }
     if (Ok) {
       // Evaluate the expression in the larger type.
-      const SCEV *Fold = getAddExpr(LargeOps, Flags, Depth + 1);
+      const SCEV *Fold = getAddExpr(LargeOps, SCEV::FlagAnyWrap, Depth + 1);
       // If it folds to something simple, use it. Otherwise, don't.
       if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
         return getTruncateExpr(Fold, Ty);
Index: llvm/trunk/test/Analysis/ScalarEvolution/truncate.ll
===================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/truncate.ll
+++ llvm/trunk/test/Analysis/ScalarEvolution/truncate.ll
@@ -73,3 +73,37 @@
   %tmp36 = icmp ugt i32 %tmp16, 52
   br i1 %tmp36, label %bb3, label %bb13
 }
+
+; Make sure that no nuw flag is assigned to %tmp27, otherwise we will have a
+; poisoned value.
+define void @no_nuw(i64 %param)  {
+
+; CHECK-LABEL: Classifying expressions for: @no_nuw
+; CHECK:         %tmp27 = add i64 %tmp20, -1
+; CHECK-NOT:    (-1 + %tmp20)<nuw>
+; CHECK-NEXT:    -->  (-1 + %tmp20) U:
+
+bb:
+  %shift = shl i64 %param, 58
+  br label %bb18
+
+bb18:                                             ; preds = %bb36, %bb
+  %tmp20 = phi i64 [ %shift, %bb ], [ 0, %bb36 ]
+  %tmp21 = phi i64 [ 0, %bb ], [ %tmp24, %bb36 ]
+  %tmp22 = phi i32 [ -6, %bb ], [ %tmp46, %bb36 ]
+  %tmp25 = add i32 %tmp22, 1
+  %tmp26 = sext i32 %tmp25 to i64
+  %tmp27 = add i64 %tmp20, -1
+  %tmp28 = mul i64 %tmp27, %tmp26
+  %tmp29 = icmp ult i64 %tmp21, 1048576
+  br i1 %tmp29, label %bb36, label %bb30
+
+bb30:                                             ; preds = %bb18
+  ret void
+
+bb36:                                             ; preds = %bb18
+  %tmp24 = add nuw i64 %tmp21, 1
+  %tmp45 = trunc i64 %tmp28 to i32
+  %tmp46 = sub i32 %tmp22, %tmp45
+  br label %bb18
+}