[PATCH] AMD GCN: Implement circular buffering.

[Andrew Stubbs]

The GCN port outputs stdout and stderr via a shared-memory interface.
Previously the buffer was limited to 1000 write operations, which was enough
for testing purposes, but easy to exhaust.

This patch implements a new circular buffering system allowing a greater
amount of output.  The interface must allow hundreds of hardware threads to
output simultaneously.  The new limit is UINT32_MAX write operations.

Unfortunately, there's no way to tell if the host side has also been updated.
This code will misbehave unless the gcn-run from GCC is also updated (although
it's fine the other way around), but that patch has already been committed.

OK?

Andrew Stubbs
Mentor Graphics / CodeSourcery

---
 newlib/libc/sys/amdgcn/write.c | 55 +++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 17 deletions(-)

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