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i965: Add a pass to demote sample interpolation intrinsics.

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When working with a non-multisampled render target, asking for "sample"
interpolation locations doesn't make sense.  We demote them to centroid.

In a couple of patches, brw_compute_barycentric_modes will begin looking
at these intrinsics to determine the barycentric modes.  fs_visitor also
will use them to code-generate pixel interpolator messages or payload
references.  Handling the "but what if it's not MSAA?" logic ahead of
time in a NIR pass simplifies things and prevents duplicated logic.

This patch doesn't actually do anything useful yet as we don't generate
these intrinsics.  I decided to keep it separate as it's self-contained,
in the hopes of shrinking the "convert everything" patch for reviewers.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
This commit is contained in:
Kenneth Graunke 2016-07-17 18:37:08 -07:00
parent 707ca00fce
commit 048a56c1fc
1 changed files with 44 additions and 0 deletions
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44
src/mesa/drivers/dri/i965/brw_fs.cpp
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@ -39,6 +39,7 @@
#include "brw_program.h"
#include "brw_dead_control_flow.h"
#include "compiler/glsl_types.h"
#include "compiler/nir/nir_builder.h"
#include "program/prog_parameter.h"
using namespace brw;
@ -6445,6 +6446,47 @@ brw_nir_set_default_interpolation(const struct brw_device_info *devinfo,
}
}
/**
* Demote per-sample barycentric intrinsics to centroid.
*
* Useful when rendering to a non-multisampled buffer.
*/
static void
demote_sample_qualifiers(nir_shader *nir)
{
nir_foreach_function(f, nir) {
if (!f->impl)
continue;
nir_builder b;
nir_builder_init(&b, f->impl);
nir_foreach_block(block, f->impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if (intrin->intrinsic != nir_intrinsic_load_barycentric_sample &&
intrin->intrinsic != nir_intrinsic_load_barycentric_at_sample)
continue;
b.cursor = nir_before_instr(instr);
nir_ssa_def *centroid =
nir_load_barycentric(&b, nir_intrinsic_load_barycentric_centroid,
nir_intrinsic_interp_mode(intrin));
nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
nir_src_for_ssa(centroid));
nir_instr_remove(instr);
}
}
nir_metadata_preserve(f->impl, (nir_metadata)
((unsigned) nir_metadata_block_index |
(unsigned) nir_metadata_dominance));
}
}
const unsigned *
brw_compile_fs(const struct brw_compiler *compiler, void *log_data,
void *mem_ctx,
@ -6465,6 +6507,8 @@ brw_compile_fs(const struct brw_compiler *compiler, void *log_data,
key->flat_shade, key->persample_interp);
brw_nir_lower_fs_inputs(shader);
brw_nir_lower_fs_outputs(shader);
if (!key->multisample_fbo)
NIR_PASS_V(shader, demote_sample_qualifiers);
shader = brw_postprocess_nir(shader, compiler->devinfo, true);
/* key->alpha_test_func means simulating alpha testing via discards,