[Flang][AMDGPU] Add a lit test for Lowering ALLOCATE/DEALLOCATE to runtime calls. (llvm#1631)

Author: ronlieb

flang/test/Lower/AMDGPU/allocate_deallocate_runtime_calls.f90

@@ -0,0 +1,28 @@
+! RUN: %flang -target amdgcn-- -mmlir -use-alloc-runtime -S -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK
+! RUN: %flang -target amdgcn-- -S -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK-NO-FLAG
+
+! Test to check if usage of flag -use-alloc-runtime results in runtime calls.
+
+subroutine allocate_deallocate()
+  real, allocatable :: x
+
+  allocate(x)
+! CHECK: call i32 @_FortranAAllocatableAllocate
+! CHECK-NO-FLAG: call ptr @malloc
+
+  deallocate(x)
+! CHECK: call i32 @_FortranAAllocatableDeallocate
+! CHECK-NO-FLAG: call void @free
+end subroutine
+
+subroutine allocate_deallocate_ptr()
+  integer, pointer :: x
+
+  allocate(x)
+! CHECK: call i32 @_FortranAPointerAllocate
+! CHECK-NO-FLAG: call i32 @_FortranAPointerAllocate
+
+  deallocate(x)
+! CHECK: call i32 @_FortranAPointerDeallocate
+! CHECK-NO-FLAG: call i32 @_FortranAPointerDeallocate
+end subroutine