Let scalar-evolution analyze loops with an unsigned comparison for the exit

condition. Fixes 1597.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40867 91177308-0d34-0410-b5e6-96231b3b80d8

test/Analysis/ScalarEvolution/2007-09-06-Unsigned.ll

@@ -0,0 +1,29 @@
+; RUN: llvm-as < %s | opt -scalar-evolution -analyze |& grep "Loop bb: ( -1 + ( -1 *  %x) +  %y) iterations!"
+
+define i32 @f(i32 %x, i32 %y) {
+entry:
+        %tmp63 = icmp ult i32 %x, %y            ; <i1> [#uses=1]
+        br i1 %tmp63, label %bb.preheader, label %bb8
+
+bb.preheader:           ; preds = %entry
+        br label %bb
+
+bb:             ; preds = %bb3, %bb.preheader
+        %x_addr.0 = phi i32 [ %tmp2, %bb3 ], [ %x, %bb.preheader ]              ; <i32> [#uses=1]
+        %tmp2 = add i32 %x_addr.0, 1            ; <i32> [#uses=3]
+        br label %bb3
+
+bb3:            ; preds = %bb
+        %tmp6 = icmp ult i32 %tmp2, %y          ; <i1> [#uses=1]
+        br i1 %tmp6, label %bb, label %bb8.loopexit
+
+bb8.loopexit:           ; preds = %bb3
+        br label %bb8
+
+bb8:            ; preds = %bb8.loopexit, %entry
+        %x_addr.1 = phi i32 [ %x, %entry ], [ %tmp2, %bb8.loopexit ]            ; <i32> [#uses=1]
+        br label %return
+
+return:         ; preds = %bb8
+        ret i32 %x_addr.1
+}