Add an implementation of Differentiation without tgmath (swiftlang#34116)

Addresses rdar://68471851

Author: edymtt

stdlib/CMakeLists.txt

@@ -66,6 +66,10 @@ option(SWIFT_ENABLE_MODULE_INTERFACES
        "Generate .swiftinterface files alongside .swiftmodule files"
        "${SWIFT_STDLIB_STABLE_ABI}")
 
+option(SWIFT_COMPILE_DIFFERENTIATION_WITHOUT_TGMATH
+       "Build Differentation without tgmath (and dependency on platform runtime libraries)"
+       FALSE)
+
 #
 # End of user-configurable options.
 #

stdlib/public/CMakeLists.txt

@@ -87,7 +87,15 @@ if(SWIFT_BUILD_STDLIB)
   add_subdirectory(SwiftOnoneSupport)
 
   if(SWIFT_ENABLE_EXPERIMENTAL_DIFFERENTIABLE_PROGRAMMING)
-    add_subdirectory(Differentiation)
+    if(SWIFT_COMPILE_DIFFERENTIATION_WITHOUT_TGMATH)
+      # Use a different CMakeLists.txt for this configuration
+      # while sharing the bulk of the code
+      # This way we will reduce any side effect on the main configuration
+      # and increase the readability of the CMake code
+      add_subdirectory(Differentiation_NoTgMath)
+    else()
+      add_subdirectory(Differentiation)
+    endif()
   endif()
 
   if(SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY)

stdlib/public/Differentiation_NoTgMath/CMakeLists.txt

@@ -0,0 +1,20 @@
+set(SOURCES_FOLDER ../Differentiation)
+
+add_swift_target_library(swift_Differentiation ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
+  ${SOURCES_FOLDER}/Differentiable.swift
+  ${SOURCES_FOLDER}/DifferentialOperators.swift
+  ${SOURCES_FOLDER}/DifferentiationUtilities.swift
+  ${SOURCES_FOLDER}/AnyDifferentiable.swift
+  ${SOURCES_FOLDER}/ArrayDifferentiation.swift
+  ${SOURCES_FOLDER}/OptionalDifferentiation.swift
+
+  GYB_SOURCES
+    ${SOURCES_FOLDER}/FloatingPointDifferentiation.swift.gyb
+    ${SOURCES_FOLDER}/SIMDDifferentiation.swift.gyb
+
+  SWIFT_COMPILE_FLAGS
+    ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
+    -parse-stdlib
+  LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
+  DARWIN_INSTALL_NAME_DIR "@rpath"
+  INSTALL_IN_COMPONENT stdlib)