diff options
Diffstat (limited to 'src/compiler/nir')
| -rw-r--r-- | src/compiler/nir/meson.build | 1 | ||||
| -rw-r--r-- | src/compiler/nir/nir.h | 1 | ||||
| -rw-r--r-- | src/compiler/nir/nir_lower_viewport_transform.c | 102 |
3 files changed, 104 insertions, 0 deletions
diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build index 4e5039e28e0..d6e7b2cc167 100644 --- a/src/compiler/nir/meson.build +++ b/src/compiler/nir/meson.build @@ -152,6 +152,7 @@ files_libnir = files( 'nir_lower_vars_to_ssa.c', 'nir_lower_var_copies.c', 'nir_lower_vec_to_movs.c', + 'nir_lower_viewport_transform.c', 'nir_lower_wpos_center.c', 'nir_lower_wpos_ytransform.c', 'nir_lower_bit_size.c', diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h index ad72a5c9222..4323f5e0413 100644 --- a/src/compiler/nir/nir.h +++ b/src/compiler/nir/nir.h @@ -3114,6 +3114,7 @@ void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask); void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask); bool nir_lower_io_to_vector(nir_shader *shader, nir_variable_mode mask); +void nir_lower_viewport_transform(nir_shader *shader); bool nir_lower_uniforms_to_ubo(nir_shader *shader, int multiplier); typedef struct nir_lower_subgroups_options { diff --git a/src/compiler/nir/nir_lower_viewport_transform.c b/src/compiler/nir/nir_lower_viewport_transform.c new file mode 100644 index 00000000000..94b54524ab7 --- /dev/null +++ b/src/compiler/nir/nir_lower_viewport_transform.c @@ -0,0 +1,102 @@ +/* + * Copyright (C) 2019 Alyssa Rosenzweig + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +/* On some hardware (particularly, all current versions of Mali GPUs), + * vertex shaders do not output gl_Position in world-space. Instead, they + * output gl_Position in transformed screen space via the "pseudo" + * position varying. Thus, this pass finds writes to gl_Position and + * changes them to transformed writes, still to gl_Position. The + * outputted screen space is still written back to VARYING_SLOT_POS, + * which is semantically ambiguous but nevertheless a good match for + * Gallium/NIR/Mali. + * + * Implements coordinate transformation as defined in section 12.5 + * "Coordinate Transformation" of the OpenGL ES 3.2 full specification. + * + * This pass must run before lower_vars/lower_io such that derefs are + * still in place. + */ + +#include "nir/nir.h" +#include "nir/nir_builder.h" + +void +nir_lower_viewport_transform(nir_shader *shader) +{ + assert(shader->info.stage == MESA_SHADER_VERTEX); + + nir_foreach_function(func, shader) { + nir_foreach_block(block, func->impl) { + nir_foreach_instr_safe(instr, block) { + if (instr->type != nir_instr_type_intrinsic) + continue; + + nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr); + if (intr->intrinsic != nir_intrinsic_store_deref) + continue; + + nir_variable *var = nir_intrinsic_get_var(intr, 0); + if (var->data.location != VARYING_SLOT_POS) + continue; + + nir_builder b; + nir_builder_init(&b, func->impl); + b.cursor = nir_before_instr(instr); + + /* Grab the source and viewport */ + nir_ssa_def *input_point = nir_ssa_for_src(&b, intr->src[1], 4); + nir_ssa_def *scale = nir_load_viewport_scale(&b); + nir_ssa_def *offset = nir_load_viewport_offset(&b); + + /* World space to normalised device coordinates to screen space */ + + nir_ssa_def *w_recip = nir_frcp(&b, nir_channel(&b, input_point, 3)); + + nir_ssa_def *ndc_point = nir_fmul(&b, + nir_channels(&b, input_point, 0x7), w_recip); + + nir_ssa_def *screen = nir_fadd(&b, + nir_fmul(&b, ndc_point, scale), offset); + + /* gl_Position will be written out in screenspace xyz, with w set to + * the reciprocal we computed earlier. The transformed w component is + * then used for perspective-correct varying interpolation. The + * transformed w component must preserve its original sign; this is + * used in depth clipping computations + */ + + nir_ssa_def *screen_space = nir_vec4(&b, + nir_channel(&b, screen, 0), + nir_channel(&b, screen, 1), + nir_channel(&b, screen, 2), + w_recip); + + nir_instr_rewrite_src(instr, &intr->src[1], + nir_src_for_ssa(screen_space)); + } + } + + nir_metadata_preserve(func->impl, nir_metadata_block_index | + nir_metadata_dominance); + } +} |