While this is not yet used, Compilation will be able to adopt this for easier testing of driver-level task execution (instead of forcing all driver-level tests to invoke the frontend, linker, etc.).
Swift SVN r12349
Instead of always calling waitpid() and looking for the termination of a task, call poll() and watch for events on the pipes which are used for buffering subtask output. When we receive a POLLIN or POLLPRI event, ask the corresponding Task to read from the pipe; when we receive a POLLHUP or POLLERR event, wait for the subtask to finish and then ask the Task to perform its post-execution tasks.
Now that the Unix implementation properly handles large amounts of subtask output, re-enable the Unix implementation (if supported).
This fixes <rdar://problem/15795234>.
Swift SVN r12293
The current implementation does not read() from each Task's pipe until execution
finishes. This causes subtasks to block in write() if the pipe is full, which
only happens if there is a large amount of output (such as in -dump-ast mode).
Fixing output buffering and reenabling the Unix TaskQueue implementation is
tracked by <rdar://problem/15795234>.
Swift SVN r12135
Due to the nature of this class, there are two implementations of TaskQueue:
a Unix-specific implementation which supports both parallel execution and output
buffering, and a default implementation which supports neither of these features.
(The default implementation uses the functions from llvm/Support/Program.h for execution.)
TaskQueue allows clients to provide a TaskBeganCallback and a TaskFinishedCallback,
each of which will be called when a new task begins or when a task finishes execution,
respectively. Clients may add tasks to the TaskQueue in either of these callbacks,
and clients can stop further execution by returning TaskFinishedResponse::StopExecution
from the TaskFinishedCallback.
Swift SVN r12059
