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i965/fs: Simplify interference scan in register coalescing.

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We were starting at the beginning of the instruction list, rather than
with the MOV instruction itself. This allows us to coalesce after
control flow.

Excluding the shaders from an unreleased title, the shader-db results:

total instructions in shared programs: 1603791 -> 1594215 (-0.60%)
instructions in affected programs:     678772 -> 669196 (-1.41%)
GAINED:                                5
LOST:                                  0

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner 2014-04-09 14:31:10 -07:00
parent 04a4e43eb2
commit 5ff1e446d4
1 changed files with 9 additions and 13 deletions
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22
src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
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@ -77,7 +77,7 @@ is_coalesce_candidate(const fs_inst *inst, const int *virtual_grf_sizes)
static bool
can_coalesce_vars(brw::fs_live_variables *live_intervals,
const exec_list *instructions, const fs_inst *inst,
const exec_list *instructions, const fs_inst *inst, int ip,
int var_to, int var_from)
{
if (!live_intervals->vars_interfere(var_from, var_to))
@ -96,21 +96,15 @@ can_coalesce_vars(brw::fs_live_variables *live_intervals,
if (live_intervals->end[var_to] > live_intervals->end[var_from])
return false;
int scan_ip = -1;
foreach_list(n, instructions) {
fs_inst *scan_inst = (fs_inst *)n;
scan_ip++;
assert(ip >= live_intervals->start[var_to]);
fs_inst *scan_inst;
for (scan_inst = (fs_inst *)inst->next;
!scan_inst->is_tail_sentinel() && ip <= live_intervals->end[var_to];
scan_inst = (fs_inst *)scan_inst->next, ip++) {
if (scan_inst->is_control_flow())
return false;
if (scan_ip <= live_intervals->start[var_to])
continue;
if (scan_ip > live_intervals->end[var_to])
break;
if (scan_inst->dst.equals(inst->dst) ||
scan_inst->dst.equals(inst->src[0]))
return false;
@ -133,9 +127,11 @@ fs_visitor::register_coalesce()
fs_inst *mov[MAX_SAMPLER_MESSAGE_SIZE];
int var_to[MAX_SAMPLER_MESSAGE_SIZE];
int var_from[MAX_SAMPLER_MESSAGE_SIZE];
int ip = -1;
foreach_list(node, &this->instructions) {
fs_inst *inst = (fs_inst *)node;
ip++;
if (!is_coalesce_candidate(inst, virtual_grf_sizes))
continue;
@ -174,7 +170,7 @@ fs_visitor::register_coalesce()
var_to[i] = live_intervals->var_from_vgrf[reg_to] + reg_to_offset[i];
var_from[i] = live_intervals->var_from_vgrf[reg_from] + i;
if (!can_coalesce_vars(live_intervals, &instructions, inst,
if (!can_coalesce_vars(live_intervals, &instructions, inst, ip,
var_to[i], var_from[i])) {
can_coalesce = false;
reg_from = -1;