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i965/vec4/nir: Emit single MOV to generate a scalar constant.

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If an immediate is written to multiple channels, we can load it in a
single writemasked MOV.

total instructions in shared programs: 6285144 -> 6261991 (-0.37%)
instructions in affected programs:     718991 -> 695838 (-3.22%)
helped:                                5762

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
This commit is contained in:
Matt Turner 2015-08-12 11:35:17 -07:00
parent 5af71fb5ac
commit 2450cbfcbc
1 changed files with 18 additions and 3 deletions
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21
src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
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@ -458,13 +458,28 @@ vec4_visitor::nir_emit_load_const(nir_load_const_instr *instr)
dst_reg reg = dst_reg(GRF, alloc.allocate(1));
reg.type = BRW_REGISTER_TYPE_F;
unsigned remaining = brw_writemask_for_size(instr->def.num_components);
/* @FIXME: consider emitting vector operations to save some MOVs in
* cases where the components are representable in 8 bits.
* By now, we emit a MOV for each component.
* For now, we emit a MOV for each distinct value.
*/
for (unsigned i = 0; i < instr->def.num_components; ++i) {
reg.writemask = 1 << i;
for (unsigned i = 0; i < instr->def.num_components; i++) {
unsigned writemask = 1 << i;
if ((remaining & writemask) == 0)
continue;
for (unsigned j = i; j < instr->def.num_components; j++) {
if (instr->value.u[i] == instr->value.u[j]) {
writemask |= 1 << j;
}
}
reg.writemask = writemask;
emit(MOV(reg, src_reg(instr->value.f[i])));
remaining &= ~writemask;
}
/* Set final writemask */