[LAA] Add test variant with backward dep with overlap in loop.

The original test @backward_dep_known_distance_less_than_btc was
incorrectly named, as all loads are completely before the first store.

Add a variant where this is not the case: @backward_dep_known_distance_less_than_btc

Author: fhahn

llvm/test/Analysis/LoopAccessAnalysis/different-strides-safe-dep-due-to-backedge-taken-count.ll

@@ -106,8 +106,10 @@ exit:
   ret void
 }
 
-define void @backward_dep_known_distance_less_than_btc(ptr %A) {
-; CHECK-LABEL: 'backward_dep_known_distance_less_than_btc'
+; TOOD: The loop should be safe without dependence, as all accesses to %l are
+; completely before the first store.
+define void @backward_dep_known_safe_due_to_backedge_taken_count(ptr %A) {
+; CHECK-LABEL: 'backward_dep_known_safe_due_to_backedge_taken_count'
 ; CHECK-NEXT:    loop:
 ; CHECK-NEXT:      Memory dependences are safe with a maximum safe vector width of 8160 bits
 ; CHECK-NEXT:      Dependences:
@@ -142,3 +144,40 @@ loop:
 exit:
   ret void
 }
+
+define void @backward_dep_known_distance_less_than_btc(ptr %A) {
+; CHECK-LABEL: 'backward_dep_known_distance_less_than_btc'
+; CHECK-NEXT:    loop:
+; CHECK-NEXT:      Memory dependences are safe with a maximum safe vector width of 4064 bits
+; CHECK-NEXT:      Dependences:
+; CHECK-NEXT:        BackwardVectorizable:
+; CHECK-NEXT:            %l = load i32, ptr %gep, align 4 ->
+; CHECK-NEXT:            store i32 %add, ptr %gep.mul.2, align 4
+; CHECK-EMPTY:
+; CHECK-NEXT:      Run-time memory checks:
+; CHECK-NEXT:      Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:      SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Expressions re-written:
+;
+entry:
+  %A.510 = getelementptr inbounds i32, ptr %A, i64 510
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %iv.mul.2 = shl nuw nsw i64 %iv, 1
+  %gep = getelementptr inbounds i32, ptr %A, i64 %iv.mul.2
+  %l = load i32, ptr %gep, align 4
+  %add = add nsw i32 %l, 5
+  %gep.mul.2 = getelementptr inbounds i32, ptr %A.510, i64 %iv
+  store i32 %add, ptr %gep.mul.2, align 4
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %iv.next, 256
+  br i1 %exitcond.not, label %exit, label %loop
+
+exit:
+  ret void
+}