[OpenMP] Fix omp_get_wtime function being marked incorrectly as readonly

OpenMP has a list of of optimistic attributes that can be attached to
known runtime functions to aid some analysis. The `omp_get_wtime`
function incorrectly used the `readonly` attribute. This is not correct
at the `omp_get_wtime` function changes values depending on some
external state. This is more correctly modeled with
`inaccessiblememonly` meaning that the value does not depend on anything
within the module, but can not be removes as it depends on external
state.

Fixes #57578

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D133360

Author: jhuber6

llvm/include/llvm/Frontend/OpenMP/OMPKinds.def

@@ -683,7 +683,7 @@ __OMP_RTL_ATTRS(omp_get_partition_num_places, GetterAttrs, AttributeSet(),
                 ParamAttrs())
 __OMP_RTL_ATTRS(omp_get_partition_place_nums, GetterAttrs, AttributeSet(),
                 ParamAttrs())
-__OMP_RTL_ATTRS(omp_get_wtime, GetterAttrs, AttributeSet(), ParamAttrs())
+__OMP_RTL_ATTRS(omp_get_wtime, GetterArgWriteAttrs, AttributeSet(), ParamAttrs())
 
 __OMP_RTL_ATTRS(omp_set_num_threads, SetterAttrs, AttributeSet(), ParamAttrs())
 __OMP_RTL_ATTRS(omp_set_dynamic, SetterAttrs, AttributeSet(), ParamAttrs())

llvm/test/Transforms/OpenMP/add_attributes.ll

@@ -1313,7 +1313,7 @@ attributes #0 = { noinline cold }
 ; OPTIMISTIC-NOT: Function Attrs
 ; OPTIMISTIC: declare dso_local void @omp_init_nest_lock_with_hint(%struct.omp_nest_lock_t*, i32)
 
-; OPTIMISTIC: ; Function Attrs: inaccessiblememonly nofree nosync nounwind readonly willreturn
+; OPTIMISTIC: ; Function Attrs: inaccessiblemem_or_argmemonly nofree nosync nounwind willreturn
 ; OPTIMISTIC-NEXT: declare dso_local double @omp_get_wtime()
 
 ; OPTIMISTIC-NOT: Function Attrs