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i965/fs: Handle conditional discards.

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The discard condition tells us which channels we want killed.  We want
to invert that condition to get the channels that should survive (remain
live) in f0.1.  Emit a CMP to negate it.

Nothing generates these today, but that will change shortly.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Kenneth Graunke 2014-08-19 15:22:43 -07:00
parent 8e62bd52f8
commit 8eb6c10999
2 changed files with 26 additions and 17 deletions
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22
src/mesa/drivers/dri/i965/brw_fs_nir.cpp
View file

@ -1258,16 +1258,22 @@ fs_visitor::nir_emit_intrinsic(nir_intrinsic_instr *instr)
bool has_indirect = false;
switch (instr->intrinsic) {
case nir_intrinsic_discard: {
case nir_intrinsic_discard:
case nir_intrinsic_discard_if: {
/* We track our discarded pixels in f0.1. By predicating on it, we can
* update just the flag bits that aren't yet discarded. By emitting a
* CMP of g0 != g0, all our currently executing channels will get turned
* off.
* update just the flag bits that aren't yet discarded. If there's no
* condition, we emit a CMP of g0 != g0, so all currently executing
* channels will get turned off.
*/
fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
BRW_REGISTER_TYPE_UW));
fs_inst *cmp = emit(CMP(reg_null_f, some_reg, some_reg,
BRW_CONDITIONAL_NZ));
fs_inst *cmp;
if (instr->intrinsic == nir_intrinsic_discard_if) {
cmp = emit(CMP(reg_null_f, get_nir_src(instr->src[0]),
fs_reg(0), BRW_CONDITIONAL_Z));
} else {
fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
BRW_REGISTER_TYPE_UW));
cmp = emit(CMP(reg_null_f, some_reg, some_reg, BRW_CONDITIONAL_NZ));
}
cmp->predicate = BRW_PREDICATE_NORMAL;
cmp->flag_subreg = 1;

21
src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
View file

@ -2415,17 +2415,20 @@ fs_visitor::visit(ir_swizzle *ir)
void
fs_visitor::visit(ir_discard *ir)
{
assert(ir->condition == NULL); /* FINISHME */
/* We track our discarded pixels in f0.1. By predicating on it, we can
* update just the flag bits that aren't yet discarded. By emitting a
* CMP of g0 != g0, all our currently executing channels will get turned
* off.
* update just the flag bits that aren't yet discarded. If there's no
* condition, we emit a CMP of g0 != g0, so all currently executing
* channels will get turned off.
*/
fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
BRW_REGISTER_TYPE_UW));
fs_inst *cmp = emit(CMP(reg_null_f, some_reg, some_reg,
BRW_CONDITIONAL_NZ));
fs_inst *cmp;
if (ir->condition) {
ir->condition->accept(this);
cmp = emit(CMP(reg_null_f, this->result, fs_reg(0), BRW_CONDITIONAL_Z));
} else {
fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
BRW_REGISTER_TYPE_UW));
cmp = emit(CMP(reg_null_f, some_reg, some_reg, BRW_CONDITIONAL_NZ));
}
cmp->predicate = BRW_PREDICATE_NORMAL;
cmp->flag_subreg = 1;