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i965/vec4: check writemask when bailing out at register coalesce

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opt_register_coalesce stopped to check previous instructions to
coalesce with if somebody else was writing on the same
destination. This can be optimized to check if somebody else was
writing to the same channels of the same destination using the
writemask.

Shader DB results (taking into account only vec4):

total instructions in shared programs: 1781593 -> 1734957 (-2.62%)
instructions in affected programs:     1238390 -> 1191754 (-3.77%)
helped:                                12782
HURT:                                  0
GAINED:                                0
LOST:                                  0

v2: removed some parenthesis, fixed indentation, as suggested by
    Matt Turner
v3: added brackets, for consistency, as suggested by Eduardo Lima

Reviewed-by: Matt Turner <mattst88@gmail.com>
(cherry picked from commit d4e29af234)
Nominated-by: Jason Ekstrand <jason@jlekstrand.net>
This commit is contained in:
Alejandro Piñeiro 2015-09-11 12:21:13 +02:00 • committed by Emil Velikov
parent 42364b33d1
commit 6766a36e19
1 changed files with 6 additions and 4 deletions
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10
src/mesa/drivers/dri/i965/brw_vec4.cpp
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@ -1105,11 +1105,13 @@ vec4_visitor::opt_register_coalesce()
if (interfered)
break;
/* If somebody else writes our destination here, we can't coalesce
* before that.
/* If somebody else writes the same channels of our destination here,
* we can't coalesce before that.
*/
if (inst->dst.in_range(scan_inst->dst, scan_inst->regs_written))
break;
if (inst->dst.in_range(scan_inst->dst, scan_inst->regs_written) &&
(inst->dst.writemask & scan_inst->dst.writemask) != 0) {
break;
}
/* Check for reads of the register we're trying to coalesce into. We
* can't go rewriting instructions above that to put some other value