Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -1268,7 +1268,11 @@
     }
     if (!hasTrunc)
       return getAddExpr(Operands);
-    UniqueSCEVs.FindNodeOrInsertPos(ID, IP);  // Mutates IP, returns NULL.
+    // In spite we checked in the beginning that ID is not in the cache,
+    // it is possible that during recursion and different modification
+    // ID came to cache, so if we found it, just return it.
+    if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP))
+      return S;
   }
 
   // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
@@ -1284,7 +1288,11 @@
     }
     if (!hasTrunc)
       return getMulExpr(Operands);
-    UniqueSCEVs.FindNodeOrInsertPos(ID, IP);  // Mutates IP, returns NULL.
+    // In spite we checked in the beginning that ID is not in the cache,
+    // it is possible that during recursion and different modification
+    // ID came to cache, so if we found it, just return it.
+    if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP))
+      return S;
   }
 
   // If the input value is a chrec scev, truncate the chrec's operands.
Index: llvm/trunk/test/Analysis/ScalarEvolution/truncate.ll
===================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/truncate.ll
+++ llvm/trunk/test/Analysis/ScalarEvolution/truncate.ll
@@ -0,0 +1,72 @@
+; RUN: opt < %s -analyze -scalar-evolution
+; RUN: opt < %s -passes='print<scalar-evolution>'
+; Regression test for assert ScalarEvolution::getTruncateExpr.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @snork(i8* %arg, i8 %arg1, i64 %arg2) {
+bb:
+  br label %bb12
+
+bb3:                                              ; preds = %bb34
+  br i1 true, label %bb4, label %bb12
+
+bb4:                                              ; preds = %bb3
+  br label %bb6
+
+bb5:                                              ; preds = %bb6
+  ret void
+
+bb6:                                              ; preds = %bb6, %bb4
+  %tmp = phi i64 [ %tmp28, %bb4 ], [ %tmp10, %bb6 ]
+  %tmp7 = phi i32 [ 3, %bb4 ], [ %tmp11, %bb6 ]
+  %tmp8 = trunc i64 %tmp to i32
+  %tmp9 = sdiv i32 %tmp8, %tmp7
+  %tmp10 = add i64 %tmp, -1
+  %tmp11 = add i32 %tmp9, %tmp7
+  br i1 true, label %bb5, label %bb6
+
+bb12:                                             ; preds = %bb3, %bb
+  br label %bb13
+
+bb13:                                             ; preds = %bb34, %bb12
+  %tmp14 = phi i64 [ %arg2, %bb12 ], [ %tmp28, %bb34 ]
+  %tmp15 = phi i8 [ %arg1, %bb12 ], [ %tmp26, %bb34 ]
+  %tmp16 = phi i32 [ 1, %bb12 ], [ %tmp35, %bb34 ]
+  %tmp17 = add i8 %tmp15, -1
+  %tmp18 = sext i8 %tmp17 to i64
+  %tmp19 = sub i64 1, %tmp14
+  %tmp20 = add i64 %tmp19, %tmp18
+  %tmp21 = trunc i64 %tmp20 to i32
+  %tmp22 = icmp eq i32 %tmp21, 0
+  br i1 %tmp22, label %bb32, label %bb23
+
+bb23:                                             ; preds = %bb13
+  br i1 true, label %bb25, label %bb24
+
+bb24:                                             ; preds = %bb23
+  br label %bb25
+
+bb25:                                             ; preds = %bb24, %bb23
+  %tmp26 = add i8 %tmp15, -2
+  %tmp27 = sext i8 %tmp26 to i64
+  %tmp28 = sub i64 %tmp27, %tmp20
+  %tmp29 = trunc i64 %tmp28 to i32
+  %tmp30 = icmp eq i32 %tmp29, 0
+  br i1 %tmp30, label %bb31, label %bb34
+
+bb31:                                             ; preds = %bb25
+  br label %bb33
+
+bb32:                                             ; preds = %bb13
+  br label %bb33
+
+bb33:                                             ; preds = %bb32, %bb31
+  unreachable
+
+bb34:                                             ; preds = %bb25
+  %tmp35 = add nuw nsw i32 %tmp16, 2
+  %tmp36 = icmp ugt i32 %tmp16, 52
+  br i1 %tmp36, label %bb3, label %bb13
+}