adding same test as frontend

Author: joaosaffran

llvm/test/CodeGen/DirectX/rootsignature-validation-fail-appending-limits-multiples.ll

@@ -0,0 +1,16 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' -mtriple=dxil-pc-shadermodel6.6-compute %s 2>&1 | FileCheck %s
+; CHECK: error: Cannot append range with implicit lower bound after an unbounded range CBV(register=2, space=0).
+
+define void @CSMain() "hlsl.shader"="compute" {
+entry:
+  ret void
+}
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!3}
+!3 = !{!"DescriptorTable", i32 0, !4, !5, !6}
+!4 = !{!"CBV", i32 1, i32 0, i32 0, i32 4294967294, i32 0}
+!5 = !{!"CBV", i32 1, i32 1, i32 0, i32 -1, i32 0}
+!6 = !{!"CBV", i32 1, i32 2, i32 0, i32 -1, i32 0}