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25 #include "nir_builder.h"
27 /* Lowing for fragment shader load_output.
29 * This pass supports the blend_equation_advanced, where a fragment
30 * shader loads the output (fragcolor) to read the current framebuffer.
31 * It does this by lowering the output read to a txf_ms_fb instruction.
32 * This instruction works similarly to a normal txf_ms except without
33 * taking a texture source argument. (The driver backend is expected
34 * to wire this up to a free texture slot which is configured to read
35 * from the framebuffer.)
37 * This should be run after lower_wpos_ytransform, because the tex
38 * coordinates should be the physical fragcoord, not the logical
41 * Note that this pass explicitly does *not* add a sampler uniform
42 * (as txf_ms_fb does not reference a texture). The driver backend
43 * is going to want nif->info.num_textures to include the count of
44 * number of textures *not* including the one it inserts to sample
45 * from the framebuffer, so it more easily knows where to insert the
46 * hidden texture to read from the fb.
50 lower_fb_read(nir_builder
*b
, nir_intrinsic_instr
*intr
)
52 b
->cursor
= nir_before_instr(&intr
->instr
);
54 nir_ssa_def
*fragcoord
= nir_load_frag_coord(b
);
55 nir_ssa_def
*sampid
= nir_load_sample_id(b
);
57 fragcoord
= nir_f2i32(b
, fragcoord
);
59 nir_tex_instr
*tex
= nir_tex_instr_create(b
->shader
, 2);
60 tex
->op
= nir_texop_txf_ms_fb
;
61 tex
->sampler_dim
= GLSL_SAMPLER_DIM_2D
;
62 tex
->coord_components
= 2;
63 tex
->dest_type
= nir_type_float
;
64 tex
->src
[0].src_type
= nir_tex_src_coord
;
65 tex
->src
[0].src
= nir_src_for_ssa(nir_channels(b
, fragcoord
, 0x3));
66 tex
->src
[1].src_type
= nir_tex_src_ms_index
;
67 tex
->src
[1].src
= nir_src_for_ssa(sampid
);
69 nir_ssa_dest_init(&tex
->instr
, &tex
->dest
, 4, 32, NULL
);
70 nir_builder_instr_insert(b
, &tex
->instr
);
72 nir_ssa_def_rewrite_uses(&intr
->dest
.ssa
, nir_src_for_ssa(&tex
->dest
.ssa
));
76 nir_lower_fb_read(nir_shader
*shader
)
78 bool progress
= false;
80 assert(shader
->info
.stage
== MESA_SHADER_FRAGMENT
);
82 nir_foreach_function(function
, shader
) {
83 nir_function_impl
*impl
= function
->impl
;
88 nir_foreach_block(block
, impl
) {
89 nir_foreach_instr_safe(instr
, block
) {
90 if (instr
->type
!= nir_instr_type_intrinsic
)
93 nir_intrinsic_instr
*intr
= nir_instr_as_intrinsic(instr
);
94 if (intr
->intrinsic
!= nir_intrinsic_load_output
)
97 /* TODO KHR_blend_equation_advanced is limited to non-MRT
98 * scenarios.. but possible there are other extensions
99 * where this pass would be useful that do support MRT?
101 * I guess for now I'll leave that as an exercise for the
104 if (nir_intrinsic_base(intr
) != 0 ||
105 nir_src_as_uint(intr
->src
[0]) != 0)
109 nir_builder_init(&b
, impl
);
110 lower_fb_read(&b
, intr
);
115 nir_metadata_preserve(impl
, nir_metadata_block_index
|
116 nir_metadata_dominance
);