[libc] Clean up GPU math implementations

Summary:
The math directory likes to do architecture specific implementations of
these math functions. For the GPU case it was complicated by the fact
that both NVPTX and AMDGPU had to go through the same code paths. Since
reworking the GPU target this is no longer the case and we can simply
use the same scheme. This patch moves all the old code into two separate
directories. This likely results in a net increase in code, but it's
easier to reason with.

Author: jhuber6

libc/cmake/modules/LLVMLibCObjectRules.cmake

@@ -307,7 +307,7 @@ function(create_entrypoint_object fq_target_name)
     ${fq_target_name}
     PROPERTIES
       ENTRYPOINT_NAME ${ADD_ENTRYPOINT_OBJ_NAME}
-      TARGET_TYPE ${ENTRYPOINT_OBJ_TARGET_TYPE}
+      TARGET_TYPE ${entrypoint_target_type}
       OBJECT_FILE "$<TARGET_OBJECTS:${fq_target_name}>"
       CXX_STANDARD ${ADD_ENTRYPOINT_OBJ_CXX_STANDARD}
       DEPS "${fq_deps_list}"

libc/src/math/CMakeLists.txt

@@ -1,17 +1,13 @@
 add_subdirectory(generic)
 if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
   add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
-elseif(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
-  # TODO: We should split this into 'nvptx' and 'amdgpu' for the GPU build.
-  add_subdirectory(${LIBC_TARGET_OS})
 endif()
 
 function(add_math_entrypoint_object name)
   # We prefer machine specific implementation if available. Hence we check
   # that first and return early if we are able to add an alias target for the
   # machine specific implementation.
   get_fq_target_name("${LIBC_TARGET_ARCHITECTURE}.${name}" fq_machine_specific_target_name)
-  get_fq_target_name("${LIBC_TARGET_OS}.${name}" fq_os_specific_target_name)
   if(TARGET ${fq_machine_specific_target_name})
     add_entrypoint_object(
       ${name}
@@ -20,28 +16,6 @@ function(add_math_entrypoint_object name)
         .${LIBC_TARGET_ARCHITECTURE}.${name}
     )
     return()
-  elseif(TARGET ${fq_os_specific_target_name})
-    add_entrypoint_object(
-      ${name}
-      ALIAS
-      DEPENDS
-        .${LIBC_TARGET_OS}.${name}
-    )
-    return()
-  endif()
-
-  # The GPU optionally depends on vendor libraries. If we emitted one of these
-  # entrypoints it means the user requested it and we should use it instead.
-  get_fq_target_name("${LIBC_TARGET_OS}.vendor.${name}" fq_vendor_specific_target_name)
-  if(TARGET ${fq_vendor_specific_target_name})
-    add_entrypoint_object(
-      ${name}
-      ALIAS
-      DEPENDS
-        .${LIBC_TARGET_OS}.vendor.${name}
-      VENDOR
-    )
-    return()
   endif()
 
   get_fq_target_name("generic.${name}" fq_generic_target_name)