add option for enabling short mangling lookups (#78122)

Author: justice-adams-apple

Runtimes/Core/CMakeLists.txt

@@ -91,6 +91,7 @@ defaulted_option(SwiftCore_ENABLE_COMPACT_ABSOLUTE_FUNCTION_POINTERS "Resolve ab
 defaulted_option(SwiftCore_ENABLE_BACKDEPLOYMENT_SUPPORT "Add symbols for runtime backdeployment")
 defaulted_option(SwiftCore_ENABLE_STDLIB_TRACING "Enable tracing in the runtime. Assumes the presence of os_log(3) and the os_signpost(3) API.")
 option(SwiftCore_ENABLE_UNICODE_DATA "Include unicode data in Swift runtimes" ON)
+option(SwiftCore_ENABLE_SHORT_MANGLING_LOOKUPS "Build with fast-path context descriptor lookups based on well-known short manglings." ON)
 
 defaulted_option(SwiftCore_ENABLE_BACKTRACING "Enable backtracing runtime support")
 defaulted_set(SwiftCore_BACKTRACER_PATH STRING "Set a fixed path to the Swift backtracer")

Runtimes/Core/runtime/CMakeLists.txt

@@ -83,7 +83,8 @@ target_compile_definitions(swiftRuntime
     $<$<BOOL:${SwiftCore_ENABLE_OVERRIDABLE_RETAIN_RELEASE}>:-DSWIFT_STDLIB_OVERRIDABLE_RETAIN_RELEASE>
     $<$<BOOL:${SwiftCore_ENABLE_MALLOC_TYPE}>:-DSWIFT_STDLIB_HAS_MALLOC_TYPE>
     $<$<BOOL:${SwiftCore_BACKTRACER_PATH}>:-DSWIFT_RUNTIME_FIXED_BACKTRACER_PATH="${SwiftCore_BACKTRACER_PATH}">
-    $<$<BOOL:${SwiftCore_ENABLE_STDLIB_TRACING}>:-DSWIFT_STDLIB_TRACING>)
+    $<$<BOOL:${SwiftCore_ENABLE_STDLIB_TRACING}>:-DSWIFT_STDLIB_TRACING>
+    $<$<BOOL:${SwiftCore_ENABLE_SHORT_MANGLING_LOOKUPS}>:-DSWIFT_STDLIB_SHORT_MANGLING_LOOKUPS>)
 
 target_include_directories(swiftRuntime PRIVATE
   "${PROJECT_BINARY_DIR}/include"