Add a testcase to loop-idiom to cover PR14241 when we start handling

strided loops again.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167287 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/LoopIdiom/basic.ll

@@ -383,4 +383,37 @@ for.end:                                          ; preds = %for.inc
 
 }
 
+define void @PR14241(i32* %s, i64 %size) {
+; Ensure that we don't form a memcpy for strided loops. Briefly, when we taught
+; LoopIdiom about memmove and strided loops, this got miscompiled into a memcpy
+; instead of a memmove. If we get the memmove transform back, this will catch
+; regressions.
+;
+; CHECK: @PR14241
 
+entry:
+  %end.idx = add i64 %size, -1
+  %end.ptr = getelementptr inbounds i32* %s, i64 %end.idx
+  br label %while.body
+; CHECK-NOT: memcpy
+;
+; FIXME: When we regain the ability to form a memmove here, this test should be
+; reversed and turned into a positive assertion.
+; CHECK-NOT: memmove
+
+while.body:
+  %phi.ptr = phi i32* [ %s, %entry ], [ %next.ptr, %while.body ]
+  %src.ptr = getelementptr inbounds i32* %phi.ptr, i64 1
+  %val = load i32* %src.ptr, align 4
+; CHECK: load
+  %dst.ptr = getelementptr inbounds i32* %phi.ptr, i64 0
+  store i32 %val, i32* %dst.ptr, align 4
+; CHECK: store
+  %next.ptr = getelementptr inbounds i32* %phi.ptr, i64 1
+  %cmp = icmp eq i32* %next.ptr, %end.ptr
+  br i1 %cmp, label %exit, label %while.body
+
+exit:
+  ret void
+; CHECK: ret void
+}