| /* |
| * 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.mode != nir_var_shader_out || |
| 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); |
| } |
| } |