Index: polly/trunk/lib/Analysis/ScopDetection.cpp
===================================================================
--- polly/trunk/lib/Analysis/ScopDetection.cpp
+++ polly/trunk/lib/Analysis/ScopDetection.cpp
@@ -524,7 +524,7 @@
   const SCEV *visitUDivExpr(const SCEVUDivExpr *Expr) { return Expr; }
 
   const SCEV *visitSMaxExpr(const SCEVSMaxExpr *Expr) {
-    if (Expr->getOperand(0)->isZero()) {
+    if ((Expr->getNumOperands() == 2) and Expr->getOperand(0)->isZero()) {
       auto Res = visit(Expr->getOperand(1));
       if (Terms)
         (*Terms).push_back(Res);
@@ -534,7 +534,7 @@
     return Expr;
   }
 
-  const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) { return visit(Expr); }
+  const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) { return Expr; }
 
   const SCEV *visitUnknown(const SCEVUnknown *Expr) { return Expr; }
 
Index: polly/trunk/test/ScopDetect/scev_remove_max.ll
===================================================================
--- polly/trunk/test/ScopDetect/scev_remove_max.ll
+++ polly/trunk/test/ScopDetect/scev_remove_max.ll
@@ -0,0 +1,40 @@
+; RUN: opt %loadPolly -polly-detect < %s
+
+; This test case helps to determine wether SCEVRemoveMax::remove produces
+; an infinite loop and a segmentation fault, if it processes, for exmaple,
+; '((-1 + (-1 * %b1)) umax {(-1 + (-1 * %yStart)),+,-1}<%.preheader>)'.
+;
+; In this case, the SCoP is invalid. However, SCoP detection failed when
+; running over it.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@vertPlane = external global i8*, align 8
+
+define fastcc void @Maze2Mech(i64 %i, i64 %b1, i64 %yStart) {
+.split:
+  br i1 undef, label %DrawSegment.exit, label %DrawSegment.exit34
+
+DrawSegment.exit34:                               ; preds = %.split
+  %tmp = icmp ugt i64 %yStart, %b1
+  %tmp1 = select i1 %tmp, i64 %b1, i64 %yStart
+  %tmp2 = load i8*, i8** @vertPlane, align 8
+  %y.04.i21 = add i64 %tmp1, 1
+  br label %.lr.ph.i24
+
+.lr.ph.i24:                                       ; preds = %.lr.ph.i24, %DrawSegment.exit34
+  %y.05.i22 = phi i64 [ %y.0.i23, %.lr.ph.i24 ], [ %y.04.i21, %DrawSegment.exit34 ]
+  %tmp3 = mul i64 %y.05.i22, undef
+  %tmp4 = add i64 %tmp3, %i
+  %tmp5 = getelementptr inbounds i8, i8* %tmp2, i64 %tmp4
+  %tmp6 = load i8, i8* %tmp5, align 1
+  %y.0.i23 = add nuw i64 %y.05.i22, 1
+  br i1 false, label %bb, label %.lr.ph.i24
+
+bb:                                               ; preds = %.lr.ph.i24
+  unreachable
+
+DrawSegment.exit:                                 ; preds = %.split
+  ret void
+}