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i965/fs: Let sat-prop ignore live ranges if producer already has sat.

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This sequence (where both x and w are used afterwards) wasn't handled.

   mul.sat x, y, z
   ...
   mov.sat w, x

We assumed that if x was used after the mov.sat, that we couldn't
propagate the saturate modifier, but in fact x was already saturated.

So ignore the live range check if the producing instruction already
saturates its result. Cuts one instruction from hundreds of TF2 shaders.

total instructions in shared programs: 1995631 -> 1994951 (-0.03%)
instructions in affected programs:     155248 -> 154568 (-0.44%)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner 2014-06-28 18:00:27 -07:00
parent e58992aedd
commit bcbb7c41b7
1 changed files with 7 additions and 4 deletions
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11
src/mesa/drivers/dri/i965/brw_fs_saturate_propagation.cpp
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@ -49,8 +49,6 @@ opt_saturate_propagation_local(fs_visitor *v, bblock_t *block)
int src_var = v->live_intervals->var_from_reg(&inst->src[0]);
int src_end_ip = v->live_intervals->end[src_var];
if (src_end_ip > ip && !inst->dst.equals(inst->src[0]))
continue;
int scan_ip = ip;
bool interfered = false;
@ -63,10 +61,15 @@ opt_saturate_propagation_local(fs_visitor *v, bblock_t *block)
scan_inst->dst.reg == inst->src[0].reg &&
scan_inst->dst.reg_offset == inst->src[0].reg_offset &&
!scan_inst->is_partial_write()) {
if (scan_inst->can_do_saturate()) {
scan_inst->saturate = true;
if (scan_inst->saturate) {
inst->saturate = false;
progress = true;
} else if (src_end_ip <= ip || inst->dst.equals(inst->src[0])) {
if (scan_inst->can_do_saturate()) {
scan_inst->saturate = true;
inst->saturate = false;
progress = true;
}
}
break;
}