[JITLink] Infer default value for -use-orc-runtime option from CMake

[sgraenitz]

Summary

If compiler-rt is enabled and the ORC runtime target for the active platform exists, we can default enable the UseOrcRuntime option in llvm-jitlink.

[sgraenitz]

This patch is based on the prototype implementation in https://github.com/lhames/llvm-project/commit/8833a7f24693f1c7a3616438718e7927c6624894

[sgraenitz]

This patch wasn't adopted. Instead, ORC opted for explicit runtime paths in https://reviews.llvm.org/rG13c8ec44e6385127f4aaba333dcad705dd5888c6

llvm/tools/llvm-jitlink/CMakeLists.txt

set(LLVM_LINK_COMPONENTS
   )
 
 add_llvm_tool(llvm-jitlink
   llvm-jitlink.cpp
   llvm-jitlink-elf.cpp
   llvm-jitlink-macho.cpp
   )
 
+# If compiler-rt is enabled in this build and the ORC runtime target
+# for our platform exists, we can default enable the UseOrcRuntime option
+# in llvm-jitlink.
+if (APPLE AND CMAKE_SYSTEM_NAME MATCHES Darwin)
+  # We cannot use get_target_property() here, because compiler-rt is configured
+  # after LLVM (so the respective target doesn't exist yet). Instead we use a
+  # generator expression, which evaluates after all targets were configured.
+  # For that to work we add a manual generation-step for the config file below.
+  set(USE_ORC_RUNTIME_DEFAULT $<TARGET_EXISTS:clang_rt.orc_osx>)
+else()
+  set(USE_ORC_RUNTIME_DEFAULT 0)
+endif()
+
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/llvm-jitlink-config.h.in
+               ${CMAKE_CURRENT_BINARY_DIR}/llvm-jitlink-config.h.conf @ONLY)
+file(GENERATE OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/llvm-jitlink-config.h
+              INPUT ${CMAKE_CURRENT_BINARY_DIR}/llvm-jitlink-config.h.conf)
+
 export_executable_symbols(llvm-jitlink)

llvm/tools/llvm-jitlink/llvm-jitlink-config.h.in

+#define LLVM_JITLINK_USE_ORC_RUNTIME_DEFAULT @USE_ORC_RUNTIME_DEFAULT@

llvm/tools/llvm-jitlink/llvm-jitlink.cpp

 
 #ifdef LLVM_ON_UNIX
 #include <netdb.h>
 #include <netinet/in.h>
 #include <sys/socket.h>
 #include <unistd.h>
 #endif // LLVM_ON_UNIX
 
+#include "llvm-jitlink-config.h"
+
 #define DEBUG_TYPE "llvm_jitlink"
 
 using namespace llvm;
 using namespace llvm::jitlink;
 using namespace llvm::orc;
 
 static cl::list<std::string> InputFiles(cl::Positional, cl::OneOrMore,
                                         cl::desc("input files"));

 static cl::opt<std::string> OutOfProcessExecutor(
     "oop-executor", cl::desc("Launch an out-of-process executor to run code"),
     cl::ValueOptional);
 
 static cl::opt<std::string> OutOfProcessExecutorConnect(
     "oop-executor-connect",
     cl::desc("Connect to an out-of-process executor via TCP"));
 
-// TODO: Default to false if compiler-rt is not built.
-static cl::opt<bool> UseOrcRuntime("use-orc-runtime",
-                                   cl::desc("Do not required/load ORC runtime"),
-                                   cl::init(true));
+static cl::opt<bool>
+    UseOrcRuntime("use-orc-runtime",
+                  cl::init(LLVM_JITLINK_USE_ORC_RUNTIME_DEFAULT));
 
 static cl::opt<std::string>
     OrcRuntimePath("orc-runtime-path", cl::desc("Add orc runtime to session"),
                    cl::init(""));
 
 ExitOnError ExitOnErr;
 
 namespace llvm {
if (OrcRuntimePath.empty()) {
              DefaultOrcRuntimePath.back() == '/')
         DefaultOrcRuntimePath.pop_back();
       if (DefaultOrcRuntimePath.endswith("bin"))
         sys::path::remove_filename(DefaultOrcRuntimePath); // remove 'bin'
       sys::path::append(DefaultOrcRuntimePath,
                         "lib/clang/12.0.0/lib/darwin/libclang_rt.orc_osx.a");
       OrcRuntimePath = DefaultOrcRuntimePath.str().str();
     }
+
+    if (!sys::fs::exists(OrcRuntimePath))
+      return make_error<StringError>(
+          formatv("Cannot find static archive for ORC runtime: {0}",
+                  OrcRuntimePath),
+          inconvertibleErrorCode());
   }
+
   return Error::success();
 }
 
 static Error loadProcessSymbols(Session &S) {
   auto FilterMainEntryPoint =
       [EPName = S.ES.intern(EntryPointName)](SymbolStringPtr Name) {
         return Name != EPName;
       };