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i965/fs: Reduce restrictions on interference in register coalescing.

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We previously only allowed coalescing registers that interfere (i.e.,
whose live ranges overlap) if the destination register's live range was
entirely inside the source's live range. This is unnecessary -- we only
need to check for interfering writes in the intersection of their live
ranges.

total instructions in shared programs: 1639470 -> 1638453 (-0.06%)
instructions in affected programs:     84751 -> 83734 (-1.20%)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner
2014-04-15 22:46:55 -07:00
parent 55de1c035c
commit f770123f58
1 changed files with 0 additions and 13 deletions
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src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
-13
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@@ -83,19 +83,6 @@ can_coalesce_vars(brw::fs_live_variables *live_intervals,
if (!live_intervals->vars_interfere(var_from, var_to))
return true;
/* We know that the live ranges of A (var_from) and B (var_to)
* interfere because of the ->vars_interfere() call above. If the end
* of B's live range is after the end of A's range, then we know two
* things:
* - the start of B's live range must be in A's live range (since we
* already know the two ranges interfere, this is the only remaining
* possibility)
* - the interference isn't of the form we're looking for (where B is
* entirely inside A)
*/
if (live_intervals->end[var_to] > live_intervals->end[var_from])
return false;
assert(ip >= live_intervals->start[var_to]);
fs_inst *scan_inst;