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- From: shmeel gutl <shmeelgutl at shmuelhome dot mine dot nu>
- To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Cc: vmakarov at redhat dot com
- Date: Mon, 19 May 2014 09:13:57 +0300
- Subject: negative latencies
- Authentication-results: sourceware.org; auth=none
Are there hooks in gcc to deal with negative latencies? In other words,
an architecture that permits an instruction to use a result from an
instruction that will be issued later.
At first glance it seems that it will will break a few things.
1) The definition of dependencies cannot come from the simple ordering
2) The scheduling problem starts to look like "get off the train 3 stops
3) The definition of live ranges needs to use actual instruction timing
information, not just instruction sequencing.
The hooks in the scheduler seem to be enough to stop damage but not
enough to take advantage of this "feature".