Index: llvm/CMakeLists.txt
===================================================================
--- llvm/CMakeLists.txt
+++ llvm/CMakeLists.txt
@@ -393,6 +393,8 @@
 
 set(LLVM_ENABLE_CURL "ON" CACHE STRING "Use libcurl for the HTTP client if available. Can be ON, OFF, or FORCE_ON")
 
+set(LLVM_ENABLE_CPP_HTTPLIB "ON" CACHE STRING "Use cpp-httplib HTTP server library if available. Can be ON, OFF, or FORCE_ON")
+
 set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")
 
 option(LLVM_ENABLE_Z3_SOLVER
Index: llvm/cmake/config-ix.cmake
===================================================================
--- llvm/cmake/config-ix.cmake
+++ llvm/cmake/config-ix.cmake
@@ -6,6 +6,7 @@
 include(CheckIncludeFile)
 include(CheckLibraryExists)
 include(CheckSymbolExists)
+include(CheckCXXSymbolExists)
 include(CheckFunctionExists)
 include(CheckStructHasMember)
 include(CheckCCompilerFlag)
@@ -180,6 +181,33 @@
   set(LLVM_ENABLE_CURL "${HAVE_CURL}")
 endif()
 
+if(LLVM_ENABLE_CPP_HTTPLIB)
+  if(LLVM_ENABLE_CPP_HTTPLIB STREQUAL FORCE_ON)
+    find_package(httplib REQUIRED)
+  else()
+    find_package(httplib)
+  endif()
+  if(HTTPLIB_FOUND)
+    # Check if the "httplib" we found is usable; for example there may be another
+    # library with the same name.
+    cmake_push_check_state()
+    list(APPEND CMAKE_REQUIRED_LIBRARIES ${HTTPLIB_LIBRARY})
+    check_cxx_symbol_exists(CPPHTTPLIB_HTTPLIB_H ${HTTPLIB_HEADER_PATH} HAVE_HTTPLIB_HEADER)
+    check_cxx_symbol_exists(httplib::default_socket_options ${HTTPLIB_HEADER_PATH} HAVE_HTTPLIB_DEFAULT_SOCKET_OPTIONS)
+    check_cxx_symbol_exists(httplib::detail::find_content_type ${HTTPLIB_HEADER_PATH} HAVE_HTTPLIB_FIND_CONTENT_TYPE)
+    if(HAVE_HTTPLIB_HEADER AND HAVE_HTTPLIB_DEFAULT_SOCKET_OPTIONS AND HAVE_HTTPLIB_FIND_CONTENT_TYPE)
+      set(HAVE_HTTPLIB YES)
+    else()
+      set(HAVE_HTTPLIB NO)
+    endif()
+    cmake_pop_check_state()
+    if(LLVM_ENABLE_CPP_HTTPLIB STREQUAL FORCE_ON AND NOT HAVE_HTTPLIB)
+      message(FATAL_ERROR "Failed to configure cpp-httplib")
+    endif()
+  endif()
+  set(LLVM_ENABLE_CPP_HTTPLIB "${HAVE_HTTPLIB}")
+endif()
+
 # Don't look for these libraries if we're using MSan, since uninstrumented third
 # party code may call MSan interceptors like strlen, leading to false positives.
 if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")