[libc++][PSTL] Make the PSTL submodules only have one header

[iana]

Summary

Module map generation for the private detail headers is easier done if each private header is by itself in a submodule. Move the __algorithm/pstl_backends into their own submodules.

[iana]

libcxx/test/libcxx/lint/lint_modulemap.sh.py

32

This isn't a perfect regex, it's only matching backend.h instead of cpu_backend.h. It's probably ok enough?

[iana]

libcxx/test/libcxx/lint/lint_modulemap.sh.py

32

It's also about to not matter because the private submodules are going to be generated.

[iana]

Add one more export

libcxx/include/module.modulemap.in

module __algorithm {
       module nth_element                     { private header "__algorithm/nth_element.h" }
       module partial_sort                    { private header "__algorithm/partial_sort.h" }
       module partial_sort_copy               { private header "__algorithm/partial_sort_copy.h" }
       module partition                       { private header "__algorithm/partition.h" }
       module partition_copy                  { private header "__algorithm/partition_copy.h" }
       module partition_point                 { private header "__algorithm/partition_point.h" }
       module pop_heap                        { private header "__algorithm/pop_heap.h" }
       module prev_permutation                { private header "__algorithm/prev_permutation.h" }
-      module pstl {
+      module pstl_backends_cpu_backend       {
         private header "__algorithm/pstl_backends/cpu_backend.h"
+        export *
+      }
+      module pstl_backends_cpu_backends_any_of {
         private header "__algorithm/pstl_backends/cpu_backends/any_of.h"
+      }
+      module pstl_backends_cpu_backends_backend {
         private header "__algorithm/pstl_backends/cpu_backends/backend.h"
-        private header "__algorithm/pstl_backends/cpu_backends/fill.h"
+        export *
+      }
+      module pstl_backends_cpu_backends_fill { private header "__algorithm/pstl_backends/cpu_backends/fill.h" }
+      module pstl_backends_cpu_backends_find_if {
         private header "__algorithm/pstl_backends/cpu_backends/find_if.h"
+      }
+      module pstl_backends_cpu_backends_for_each {
         private header "__algorithm/pstl_backends/cpu_backends/for_each.h"
+      }
+      module pstl_backends_cpu_backends_serial {
         private header "__algorithm/pstl_backends/cpu_backends/serial.h"
       }
       module push_heap                       { private header "__algorithm/push_heap.h" }
       module ranges_adjacent_find            { private header "__algorithm/ranges_adjacent_find.h" }
       module ranges_all_of                   { private header "__algorithm/ranges_all_of.h" }
       module ranges_any_of                   { private header "__algorithm/ranges_any_of.h" }
       module ranges_binary_search {
         private header "__algorithm/ranges_binary_search.h"

libcxx/test/libcxx/lint/lint_modulemap.sh.py

with open(modulemap_name, 'r') as f:
                     # It's a top-level private header, such as <__bit_reference>.
                     pass
                 elif re.match(r'^\s*module (\w+)\s+[{] private (textual )?header "__(\w+/)*\1[.]h" [}]', line):
                     # It's a private submodule, such as <__utility/swap.h>.
                     pass
                 elif re.match(r'^\s*module (\w+)_fwd\s+[{] private header "__fwd/\1[.]h" [}]', line):
                     # It's a private submodule with forward declarations, such as <__fwd/span.h>.
                     pass
+                elif re.match(r'^\s*module (?:\w+_)*(\w+)\s+[{] private (textual )?header "__(\w+/)*\1[.]h" [}]', line):
+                    # It's a private pstl submodule, such as <__algorithm/pstl_backends/cpu_backend.h>
+                    pass
                 else:
                     okay = False
                     print("LINE DOESN'T MATCH REGEX in libcxx/include/module.modulemap.in!")
                     print(line)
                 # Check that these lines are alphabetized.
                 if (prevline is not None) and (line < prevline):
                     okay = False
                     print('LINES OUT OF ORDER in libcxx/include/module.modulemap.in!')
                     print(prevline)
                     print(line)
                 prevline = line
             else:
                 prevline = None
     assert okay