tree c6a1034d7fade566abc555c1c0f53cb4be05230c
parent 50dce07c8dd6ea205f7ed0c5689237cde40c5796
author Dean Michael Berris <dberris@google.com> 1537315172 +0000
committer Dean Michael Berris <dberris@google.com> 1537315172 +0000

[XRay][compiler-rt] FDRLogWriter Abstraction

Summary:
This change introduces an `FDRLogWriter` type which is responsible for
serialising metadata and function records to character buffers. This is
the first step in a refactoring of the implementation of the FDR runtime
to allow for more granular testing of the individual components of the
implementation.

The main contribution of this change is a means of hiding the details of
how specific records are written to a buffer, and for managing the
extents of these buffers. We make use of C++ features (templates and
some metaprogramming) to reduce repetition in the act of writing out
specific kinds of records to the buffer.

In this process, we make a number of changes across both LLVM and
compiler-rt to allow us to use the `Trace` abstraction defined in the
LLVM project in the testing of the runtime implementation. This gives us
a closer end-to-end test which version-locks the runtime implementation
with the loading implementation in LLVM.

We also allow using gmock in compiler-rt unit tests, by adding the
requisite definitions in the `AddCompilerRT.cmake` module.

Finally, we've gone ahead and updated the FDR logging implementation to
use the FDRLogWriter for the lowest-level record-writing details.

Following patches will isolate the state machine transitions which
manage the set-up and tear-down of the buffers we're using in multiple
threads.

Reviewers: mboerger, eizan

Subscribers: mgorny, jfb, llvm-commits

Differential Revision: https://reviews.llvm.org/D52220

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342518 91177308-0d34-0410-b5e6-96231b3b80d8