[compiler-rt][XRay] Address follow-up comments to initial interface and initialisation code

This addresses some comments from D21612, which contains the following changes:

- Update __xray_patch() and __xray_unpatch() API documentation to not imply asynchrony.
- Introduce a scope cleanup mechanism to make sure we can roll-back changes to the XRayPatching global atomic.
- Introduce a few more comments for potential extension points for other platforms (for the implementation details of patching and un-patching).

Reviewers: eugenis, rnk, kcc, echristo, majnemer

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D22911

llvm-svn: 277124

1 files changed, 7 insertions, 15 deletions

diff --git a/compiler-rt/include/xray/xray_interface.h b/compiler-rt/include/xray/xray_interface.h
index b8a0a61920b..22f137d110f 100644
--- a/compiler-rt/include/xray/xray_interface.h
+++ b/compiler-rt/include/xray/xray_interface.h
@@ -41,26 +41,18 @@ extern int __xray_remove_handler();
 
 enum XRayPatchingStatus {
   NOT_INITIALIZED = 0,
-  NOTIFIED = 1,
+  SUCCESS = 1,
   ONGOING = 2,
-  FAILED = 3
+  FAILED = 3,
 };
 
-// This tells XRay to patch the instrumentation points. This is an asynchronous
-// process, and returns the following status in specific cases:
-//
-//   - 0 : XRay is not initialized.
-//   - 1 : We've done the notification.
-//   - 2 : Patching / un-patching is on-going.
+// This tells XRay to patch the instrumentation points. See XRayPatchingStatus
+// for possible result values.
 extern XRayPatchingStatus __xray_patch();
 
-// Reverses the effect of __xray_patch(). This is an asynchronous process, and
-// returns the following status in specific cases.
-//
-//   - 0 : XRay is not initialized.
-//   - 1 : We've done the notification.
-//   - 2 : Patching / un-patching is on-going.
-extern int __xray_unpatch();
+// Reverses the effect of __xray_patch(). See XRayPatchingStatus for possible
+// result values.
+extern XRayPatchingStatus __xray_unpatch();
 }
 
 #endif