[XRay][compiler-rt] Implement logging implementation registration

Summary:
This change allows for registration of multiple logging implementations
through a central mechanism in XRay, mapping an implementation to a
"mode". Modes are strings that are used as keys to determine which
implementation to install through a single API. This mechanism allows
users to choose which implementation to install either from the
environment variable 'XRAY_OPTIONS' with the `xray_mode=` flag, or
programmatically using the `__xray_select_mode(...)` function.

Here, we introduce two API functions for the XRay logging:

__xray_log_register_mode(Mode, Impl): Associates an XRayLogImpl to a
string Mode. We can only have one implementation associated with a given
Mode.

__xray_log_select_mode(Mode): Finds the associated Impl for Mode and
installs it as if by calling `__xray_set_log_impl(...)`.

Along with these changes, we also deprecate the xray_naive_log and
xray_fdr_log flags and encourage users to instead use the xray_mode
flag.

Reviewers: kpw, dblaikie, eizan, pelikan

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D40703

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@319759 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 10 deletions

diff --git a/lib/xray/xray_fdr_logging.cc b/lib/xray/xray_fdr_logging.cc
index ca764022f..1bfa10c21 100644
--- a/lib/xray/xray_fdr_logging.cc
+++ b/lib/xray/xray_fdr_logging.cc
@@ -362,16 +362,25 @@ XRayLogInitStatus fdrLoggingInit(std::size_t BufferSize, std::size_t BufferMax,
   return XRayLogInitStatus::XRAY_LOG_INITIALIZED;
 }
 
-} // namespace __xray
-
-static auto UNUSED Unused = [] {
+bool fdrLogDynamicInitializer() XRAY_NEVER_INSTRUMENT {
   using namespace __xray;
-  if (flags()->xray_fdr_log) {
-    XRayLogImpl Impl{
-        fdrLoggingInit, fdrLoggingFinalize, fdrLoggingHandleArg0,
-        fdrLoggingFlush,
-    };
+  XRayLogImpl Impl{
+      fdrLoggingInit,
+      fdrLoggingFinalize,
+      fdrLoggingHandleArg0,
+      fdrLoggingFlush,
+  };
+  auto RegistrationResult = __xray_log_register_mode("xray-fdr", Impl);
+  if (RegistrationResult != XRayLogRegisterStatus::XRAY_REGISTRATION_OK &&
+      __sanitizer::Verbosity())
+    Report("Cannot register XRay FDR mode to 'xray-fdr'; error = %d\n",
+           RegistrationResult);
+  if (flags()->xray_fdr_log ||
+      !__sanitizer::internal_strcmp(flags()->xray_mode, "xray-fdr"))
     __xray_set_log_impl(Impl);
-  }
   return true;
-}();
+}
+
+} // namespace __xray
+
+static auto UNUSED Unused = __xray::fdrLogDynamicInitializer();