Index: llvm/CMakeLists.txt
===================================================================
--- llvm/CMakeLists.txt
+++ llvm/CMakeLists.txt
@@ -391,6 +391,8 @@
 
 set(LLVM_ENABLE_ZLIB "ON" CACHE STRING "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON")
 
+set(LLVM_ENABLE_CURL "ON" CACHE STRING "Use libcurl for the HTTP client 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/include/llvm/Support/HTTPClient.h
===================================================================
--- llvm/include/llvm/Support/HTTPClient.h
+++ llvm/include/llvm/Support/HTTPClient.h
@@ -78,6 +78,9 @@
 
 /// A reusable client that can perform HTTPRequests through a network socket.
 class HTTPClient {
+#ifdef LLVM_ENABLE_CURL
+  void *Curl = nullptr;
+#endif
   static bool IsInitialized;
 
 public:
Index: llvm/lib/Support/CMakeLists.txt
===================================================================
--- llvm/lib/Support/CMakeLists.txt
+++ llvm/lib/Support/CMakeLists.txt
@@ -74,6 +74,11 @@
   set(system_libs ${system_libs} ${Z3_LIBRARIES})
 endif()
 
+# Link LibCURL if the user wants it
+if (LLVM_ENABLE_CURL)
+  set(system_libs ${system_libs} ${CURL_LIBRARIES})
+endif()
+
 # Override the C runtime allocator on Windows and embed it into LLVM tools & libraries
 if(LLVM_INTEGRATED_CRT_ALLOC)
   if (CMAKE_BUILD_TYPE AND NOT ${LLVM_USE_CRT_${uppercase_CMAKE_BUILD_TYPE}} MATCHES "^(MT|MTd)$")
Index: llvm/lib/Support/HTTPClient.cpp
===================================================================
--- llvm/lib/Support/HTTPClient.cpp
+++ llvm/lib/Support/HTTPClient.cpp
@@ -19,6 +19,9 @@
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
+#ifdef LLVM_ENABLE_CURL
+#include <curl/curl.h>
+#endif
 
 using namespace llvm;
 
@@ -76,6 +79,105 @@
   return perform(Request);
 }
 
+#ifdef LLVM_ENABLE_CURL
+
+bool HTTPClient::isAvailable() { return true; }
+
+bool HTTPClient::IsInitialized = false;
+
+void HTTPClient::initialize() {
+  if (!IsInitialized) {
+    curl_global_init(CURL_GLOBAL_ALL);
+    IsInitialized = true;
+  }
+}
+
+void HTTPClient::cleanup() {
+  if (IsInitialized) {
+    curl_global_cleanup();
+    IsInitialized = false;
+  }
+}
+
+HTTPClient::HTTPClient() {
+  assert(IsInitialized &&
+         "Must call HTTPClient::initialize() at the beginning of main().");
+  if (Curl)
+    return;
+  assert(Curl = curl_easy_init() && "Curl could not be initialized.");
+  // Set the callback hooks.
+  curl_easy_setopt(Curl, CURLOPT_WRITEFUNCTION, curlWriteFunction);
+  curl_easy_setopt(Curl, CURLOPT_HEADERFUNCTION, curlHeaderFunction);
+}
+
+HTTPClient::~HTTPClient() { curl_easy_cleanup(Curl); }
+
+/// CurlHTTPRequest and the curl{HeaderLine,BodyChunk}Hook functions are
+/// implementation details used to work with Curl. Curl makes callbacks with a
+/// single customizable pointer parameter.
+struct CurlHTTPRequest {
+  CurlHTTPRequest(HTTPResponseHandler &Handler) : Handler(Handler) {}
+  void storeError(Error &Err) {
+    ErrorState = joinErrors(std::move(Err), std::move(ErrorState));
+  }
+  HTTPResponseHandler &Handler;
+  llvm::Error ErrorState = Error::success();
+};
+
+static size_t curlHeaderFunction(char *Contents, size_t Size, size_t NMemb,
+                                 CurlHTTPRequest *CurlRequest) {
+  assert(Size == 1 && "The Size passed by libCURL to CURLOPT_HEADERFUNCTION "
+                      "should always be 1.");
+  if (Error Err =
+          CurlRequest->Handler.handleHeaderLine(StringRef(Contents, NMemb))) {
+    CurlRequest->storeError(Err);
+    return 0;
+  }
+  return NMemb;
+}
+
+static size_t curlWriteFunction(char *Contents, size_t Size, size_t NMemb,
+                                CurlHTTPRequest *CurlRequest) {
+  Size *= NMemb;
+  if (Error Err =
+          CurlRequest->Handler.handleBodyChunk(StringRef(Contents, Size))) {
+    CurlRequest->storeError(Err);
+    return 0;
+  }
+  return Size;
+}
+
+Error HTTPClient::perform(const HTTPRequest &Request,
+                          HTTPResponseHandler &Handler) {
+  if (Request.Method != HTTPMethod::GET)
+    return createStringError(errc::invalid_argument,
+                             "Unsupported CURL request method.");
+
+  SmallString<128> Url = Request.Url;
+  curl_easy_setopt(Curl, CURLOPT_URL, Url.c_str());
+  curl_easy_setopt(Curl, CURLOPT_FOLLOWLOCATION, Request.FollowRedirects);
+
+  CurlHTTPRequest CurlRequest(Handler);
+  curl_easy_setopt(Curl, CURLOPT_WRITEDATA, &CurlRequest);
+  curl_easy_setopt(Curl, CURLOPT_HEADERDATA, &CurlRequest);
+  CURLcode CurlRes = curl_easy_perform(Curl);
+  if (CurlRes != CURLE_OK)
+    return joinErrors(std::move(CurlRequest.ErrorState),
+                      createStringError(errc::io_error,
+                                        "curl_easy_perform() failed: %s\n",
+                                        curl_easy_strerror(CurlRes)));
+  if (CurlRequest.ErrorState)
+    return std::move(CurlRequest.ErrorState);
+
+  unsigned Code;
+  curl_easy_getinfo(Curl, CURLINFO_RESPONSE_CODE, &Code);
+  if (Error Err = Handler.handleStatusCode(Code))
+    return Err;
+  return std::move(CurlRequest.ErrorState);
+}
+
+#else
+
 HTTPClient::HTTPClient() {}
 
 HTTPClient::~HTTPClient() {}
@@ -92,3 +194,5 @@
                           HTTPResponseHandler &Handler) {
   llvm_unreachable("No HTTP Client implementation available.");
 }
+
+#endif