[SCEV] NFC - add testcase for get accurate range for AddExpr

Author: czhengsz

llvm/test/Analysis/ScalarEvolution/range_nw_flag.ll

@@ -0,0 +1,21 @@
+; RUN: opt < %s -S -analyze -scalar-evolution | FileCheck %s
+
+; copied from flags-from-poison.ll
+; CHECK-LABEL: @test-add-nuw
+; CHECK: -->  {(1 + %offset)<nuw>,+,1}<nuw><%loop> U: full-set S: full-set
+define void @test-add-nuw(float* %input, i32 %offset, i32 %numIterations) {
+entry:
+  br label %loop
+loop:
+  %i = phi i32 [ %nexti, %loop ], [ 0, %entry ]
+  %nexti = add nuw i32 %i, 1
+  %index32 = add nuw i32 %nexti, %offset
+  %ptr = getelementptr inbounds float, float* %input, i32 %index32
+  %f = load float, float* %ptr, align 4
+  %exitcond = icmp eq i32 %nexti, %numIterations
+  br i1 %exitcond, label %exit, label %loop
+
+exit:
+  ret void
+}
+