Mesa (master): i965/fs: Add a note explaining a detail of register_coalesce_2().
Eric Anholt
anholt at kemper.freedesktop.org
Sat Dec 15 00:26:26 UTC 2012
Module: Mesa
Branch: master
Commit: 78ce522932e8c356880c7ca10dace4b6fe6cf313
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=78ce522932e8c356880c7ca10dace4b6fe6cf313
Author: Eric Anholt <eric at anholt.net>
Date: Fri Nov 30 15:54:19 2012 -0800
i965/fs: Add a note explaining a detail of register_coalesce_2().
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 21 +++++++++++++++++++++
1 files changed, 21 insertions(+), 0 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 5d765e0..94d200e 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1855,7 +1855,28 @@ fs_visitor::register_coalesce_2()
}
inst->remove();
+
+ /* We don't need to recalculate live intervals inside the loop despite
+ * flagging live_intervals_valid because we only use live intervals for
+ * the interferes test, and we must have had a situation where the
+ * intervals were:
+ *
+ * from to
+ * ^
+ * |
+ * v
+ * ^
+ * |
+ * v
+ *
+ * Some register R that might get coalesced with one of these two could
+ * only be referencing "to", otherwise "from"'s range would have been
+ * longer. R's range could also only start at the end of "to" or later,
+ * otherwise it will conflict with "to" when we try to coalesce "to"
+ * into Rw anyway.
+ */
live_intervals_valid = false;
+
progress = true;
continue;
}
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