src/compiler/nir/nir_lower_wpos_ytransform.c

   1 /*
   2  * Copyright © 2015 Red Hat
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  */
  23
  24 #include "nir.h"
  25 #include "nir_builder.h"
  26 #include "program/prog_instruction.h"
  27
  28 /* Lower gl_FragCoord (and fddy) to account for driver's requested coordinate-
  29  * origin and pixel-center vs. shader.  If transformation is required, a
  30  * gl_FbWposYTransform uniform is inserted (with the specified state-slots)
  31  * and additional instructions are inserted to transform gl_FragCoord (and
  32  * fddy src arg).
  33  *
  34  * This is based on the logic in emit_wpos()/emit_wpos_adjustment() in TGSI
  35  * compiler.
  36  *
  37  * Run before nir_lower_io.
  38  */
  39
  40 typedef struct {
  41    const nir_lower_wpos_ytransform_options *options;
  42    nir_shader   *shader;
  43    nir_builder   b;
  44    nir_variable *transform;
  45 } lower_wpos_ytransform_state;
  46
  47 static nir_ssa_def *
  48 get_transform(lower_wpos_ytransform_state *state)
  49 {
  50    if (state->transform == NULL) {
  51       /* NOTE: name must be prefixed w/ "gl_" to trigger slot based
  52        * special handling in uniform setup:
  53        */
  54       nir_variable *var = nir_variable_create(state->shader,
  55                                               nir_var_uniform,
  56                                               glsl_vec4_type(),
  57                                               "gl_FbWposYTransform");
  58
  59       var->num_state_slots = 1;
  60       var->state_slots = ralloc_array(var, nir_state_slot, 1);
  61       var->state_slots[0].swizzle = SWIZZLE_XYZW;
  62       memcpy(var->state_slots[0].tokens, state->options->state_tokens,
  63              sizeof(var->state_slots[0].tokens));
  64
  65       state->transform = var;
  66    }
  67    return nir_load_var(&state->b, state->transform);
  68 }
  69
  70 /* NIR equiv of TGSI CMP instruction: */
  71 static nir_ssa_def *
  72 nir_cmp(nir_builder *b, nir_ssa_def *src0, nir_ssa_def *src1, nir_ssa_def *src2)
  73 {
  74    return nir_bcsel(b, nir_flt(b, src0, nir_imm_float(b, 0.0)), src1, src2);
  75 }
  76
  77 /* see emit_wpos_adjustment() in st_mesa_to_tgsi.c */
  78 static void
  79 emit_wpos_adjustment(lower_wpos_ytransform_state *state,
  80                      nir_intrinsic_instr *intr, nir_variable *fragcoord,
  81                      bool invert, float adjX, float adjY[2])
  82 {
  83    nir_builder *b = &state->b;
  84    nir_ssa_def *wpostrans, *wpos_temp, *wpos_temp_y, *wpos_input;
  85
  86    assert(intr->dest.is_ssa);
  87
  88    b->cursor = nir_before_instr(&intr->instr);
  89
  90    wpostrans = get_transform(state);
  91    wpos_input = nir_load_var(b, fragcoord);
  92
  93    /* First, apply the coordinate shift: */
  94    if (adjX || adjY[0] || adjY[1]) {
  95       if (adjY[0] != adjY[1]) {
  96          /* Adjust the y coordinate by adjY[1] or adjY[0] respectively
  97           * depending on whether inversion is actually going to be applied
  98           * or not, which is determined by testing against the inversion
  99           * state variable used below, which will be either +1 or -1.
 100           */
 101          nir_ssa_def *adj_temp;
 102
 103          adj_temp = nir_cmp(b,
 104                             nir_channel(b, wpostrans, invert ? 2 : 0),
 105                             nir_imm_vec4(b, adjX, adjY[0], 0.0f, 0.0f),
 106                             nir_imm_vec4(b, adjX, adjY[1], 0.0f, 0.0f));
 107
 108          wpos_temp = nir_fadd(b, wpos_input, adj_temp);
 109       } else {
 110          wpos_temp = nir_fadd(b,
 111                               wpos_input,
 112                               nir_imm_vec4(b, adjX, adjY[0], 0.0f, 0.0f));
 113       }
 114       wpos_input = wpos_temp;
 115    } else {
 116       /* MOV wpos_temp, input[wpos]
 117        */
 118       wpos_temp = wpos_input;
 119    }
 120
 121    /* Now the conditional y flip: STATE_FB_WPOS_Y_TRANSFORM.xy/zw will be
 122     * inversion/identity, or the other way around if we're drawing to an FBO.
 123     */
 124    if (invert) {
 125       /* wpos_temp.y = wpos_input * wpostrans.xxxx + wpostrans.yyyy */
 126       wpos_temp_y = nir_fadd(b, nir_fmul(b, nir_channel(b, wpos_temp, 1),
 127                                             nir_channel(b, wpostrans, 0)),
 128                                 nir_channel(b, wpostrans, 1));
 129    } else {
 130       /* wpos_temp.y = wpos_input * wpostrans.zzzz + wpostrans.wwww */
 131       wpos_temp_y = nir_fadd(b, nir_fmul(b, nir_channel(b, wpos_temp, 1),
 132                                             nir_channel(b, wpostrans, 2)),
 133                                 nir_channel(b, wpostrans, 3));
 134    }
 135
 136    wpos_temp = nir_vec4(b,
 137                         nir_channel(b, wpos_temp, 0),
 138                         wpos_temp_y,
 139                         nir_channel(b, wpos_temp, 2),
 140                         nir_channel(b, wpos_temp, 3));
 141
 142    nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(wpos_temp));
 143 }
 144
 145 static void
 146 lower_fragcoord(lower_wpos_ytransform_state *state,
 147                 nir_intrinsic_instr *intr, nir_variable *fragcoord)
 148 {
 149    const nir_lower_wpos_ytransform_options *options = state->options;
 150    float adjX = 0.0f;
 151    float adjY[2] = { 0.0f, 0.0f };
 152    bool invert = false;
 153
 154    /* Based on logic in emit_wpos():
 155     *
 156     * Query the pixel center conventions supported by the pipe driver and set
 157     * adjX, adjY to help out if it cannot handle the requested one internally.
 158     *
 159     * The bias of the y-coordinate depends on whether y-inversion takes place
 160     * (adjY[1]) or not (adjY[0]), which is in turn dependent on whether we are
 161     * drawing to an FBO (causes additional inversion), and whether the pipe
 162     * driver origin and the requested origin differ (the latter condition is
 163     * stored in the 'invert' variable).
 164     *
 165     * For height = 100 (i = integer, h = half-integer, l = lower, u = upper):
 166     *
 167     * center shift only:
 168     * i -> h: +0.5
 169     * h -> i: -0.5
 170     *
 171     * inversion only:
 172     * l,i -> u,i: ( 0.0 + 1.0) * -1 + 100 = 99
 173     * l,h -> u,h: ( 0.5 + 0.0) * -1 + 100 = 99.5
 174     * u,i -> l,i: (99.0 + 1.0) * -1 + 100 = 0
 175     * u,h -> l,h: (99.5 + 0.0) * -1 + 100 = 0.5
 176     *
 177     * inversion and center shift:
 178     * l,i -> u,h: ( 0.0 + 0.5) * -1 + 100 = 99.5
 179     * l,h -> u,i: ( 0.5 + 0.5) * -1 + 100 = 99
 180     * u,i -> l,h: (99.0 + 0.5) * -1 + 100 = 0.5
 181     * u,h -> l,i: (99.5 + 0.5) * -1 + 100 = 0
 182     */
 183
 184    if (fragcoord->data.origin_upper_left) {
 185       /* Fragment shader wants origin in upper-left */
 186       if (options->fs_coord_origin_upper_left) {
 187          /* the driver supports upper-left origin */
 188       } else if (options->fs_coord_origin_lower_left) {
 189          /* the driver supports lower-left origin, need to invert Y */
 190          invert = true;
 191       } else {
 192          unreachable("invalid options");
 193       }
 194    } else {
 195       /* Fragment shader wants origin in lower-left */
 196       if (options->fs_coord_origin_lower_left) {
 197          /* the driver supports lower-left origin */
 198       } else if (options->fs_coord_origin_upper_left) {
 199          /* the driver supports upper-left origin, need to invert Y */
 200          invert = true;
 201       } else {
 202          unreachable("invalid options");
 203       }
 204    }
 205
 206    if (fragcoord->data.pixel_center_integer) {
 207       /* Fragment shader wants pixel center integer */
 208       if (options->fs_coord_pixel_center_integer) {
 209          /* the driver supports pixel center integer */
 210          adjY[1] = 1.0f;
 211       } else if (options->fs_coord_pixel_center_half_integer) {
 212          /* the driver supports pixel center half integer, need to bias X,Y */
 213          adjX = -0.5f;
 214          adjY[0] = -0.5f;
 215          adjY[1] = 0.5f;
 216       } else {
 217          unreachable("invalid options");
 218       }
 219    } else {
 220       /* Fragment shader wants pixel center half integer */
 221       if (options->fs_coord_pixel_center_half_integer) {
 222          /* the driver supports pixel center half integer */
 223       } else if (options->fs_coord_pixel_center_integer) {
 224          /* the driver supports pixel center integer, need to bias X,Y */
 225          adjX = adjY[0] = adjY[1] = 0.5f;
 226       } else {
 227          unreachable("invalid options");
 228       }
 229    }
 230
 231    emit_wpos_adjustment(state, intr, fragcoord, invert, adjX, adjY);
 232 }
 233
 234 /* turns 'fddy(p)' into 'fddy(fmul(p, transform.x))' */
 235 static void
 236 lower_fddy(lower_wpos_ytransform_state *state, nir_alu_instr *fddy)
 237 {
 238    nir_builder *b = &state->b;
 239    nir_ssa_def *p, *pt, *trans;
 240
 241    b->cursor = nir_before_instr(&fddy->instr);
 242
 243    p = nir_ssa_for_alu_src(b, fddy, 0);
 244    trans = get_transform(state);
 245    pt = nir_fmul(b, p, nir_channel(b, trans, 0));
 246
 247    nir_instr_rewrite_src(&fddy->instr,
 248                          &fddy->src[0].src,
 249                          nir_src_for_ssa(pt));
 250
 251    for (unsigned i = 0; i < 4; i++)
 252       fddy->src[0].swizzle[i] = MIN2(i, pt->num_components - 1);
 253 }
 254
 255 /* Multiply interp_deref_at_offset's offset by transform.x to flip it. */
 256 static void
 257 lower_interp_deref_at_offset(lower_wpos_ytransform_state *state,
 258                            nir_intrinsic_instr *interp)
 259 {
 260    nir_builder *b = &state->b;
 261    nir_ssa_def *offset;
 262    nir_ssa_def *flip_y;
 263
 264    b->cursor = nir_before_instr(&interp->instr);
 265
 266    offset = nir_ssa_for_src(b, interp->src[1], 2);
 267    flip_y = nir_fmul(b, nir_channel(b, offset, 1),
 268                         nir_channel(b, get_transform(state), 0));
 269    nir_instr_rewrite_src(&interp->instr, &interp->src[1],
 270                          nir_src_for_ssa(nir_vec2(b, nir_channel(b, offset, 0),
 271                                                      flip_y)));
 272 }
 273
 274 static void
 275 lower_interp_var_at_offset(lower_wpos_ytransform_state *state,
 276                            nir_intrinsic_instr *interp)
 277 {
 278    nir_builder *b = &state->b;
 279    nir_ssa_def *offset;
 280    nir_ssa_def *flip_y;
 281
 282    b->cursor = nir_before_instr(&interp->instr);
 283
 284    offset = nir_ssa_for_src(b, interp->src[0], 2);
 285    flip_y = nir_fmul(b, nir_channel(b, offset, 1),
 286                         nir_channel(b, get_transform(state), 0));
 287    nir_instr_rewrite_src(&interp->instr, &interp->src[0],
 288                          nir_src_for_ssa(nir_vec2(b, nir_channel(b, offset, 0),
 289                                                      flip_y)));
 290 }
 291
 292 static void
 293 lower_load_sample_pos(lower_wpos_ytransform_state *state,
 294                       nir_intrinsic_instr *intr)
 295 {
 296    nir_builder *b = &state->b;
 297    b->cursor = nir_after_instr(&intr->instr);
 298
 299    nir_ssa_def *pos = &intr->dest.ssa;
 300    nir_ssa_def *scale = nir_channel(b, get_transform(state), 0);
 301    nir_ssa_def *neg_scale = nir_channel(b, get_transform(state), 2);
 302    /* Either y or 1-y for scale equal to 1 or -1 respectively. */
 303    nir_ssa_def *flipped_y =
 304                nir_fadd(b, nir_fmax(b, neg_scale, nir_imm_float(b, 0.0)),
 305                         nir_fmul(b, nir_channel(b, pos, 1), scale));
 306    nir_ssa_def *flipped_pos = nir_vec2(b, nir_channel(b, pos, 0), flipped_y);
 307
 308    nir_ssa_def_rewrite_uses_after(&intr->dest.ssa, nir_src_for_ssa(flipped_pos),
 309                                   flipped_pos->parent_instr);
 310 }
 311
 312 static void
 313 lower_wpos_ytransform_block(lower_wpos_ytransform_state *state, nir_block *block)
 314 {
 315    nir_foreach_instr_safe(instr, block) {
 316       if (instr->type == nir_instr_type_intrinsic) {
 317          nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 318          if (intr->intrinsic == nir_intrinsic_load_deref) {
 319             nir_deref_instr *deref = nir_src_as_deref(intr->src[0]);
 320             nir_variable *var = nir_deref_instr_get_variable(deref);
 321
 322             if ((var->data.mode == nir_var_shader_in &&
 323                  var->data.location == VARYING_SLOT_POS) ||
 324                 (var->data.mode == nir_var_system_value &&
 325                  var->data.location == SYSTEM_VALUE_FRAG_COORD)) {
 326                /* gl_FragCoord should not have array/struct derefs: */
 327                lower_fragcoord(state, intr, var);
 328             } else if (var->data.mode == nir_var_system_value &&
 329                        var->data.location == SYSTEM_VALUE_SAMPLE_POS) {
 330                lower_load_sample_pos(state, intr);
 331             }
 332          } else if (intr->intrinsic == nir_intrinsic_load_var) {
 333             nir_deref_var *dvar = intr->variables[0];
 334             nir_variable *var = dvar->var;
 335
 336             if ((var->data.mode == nir_var_shader_in &&
 337                  var->data.location == VARYING_SLOT_POS) ||
 338                 (var->data.mode == nir_var_system_value &&
 339                  var->data.location == SYSTEM_VALUE_FRAG_COORD)) {
 340                /* gl_FragCoord should not have array/struct derefs: */
 341                assert(dvar->deref.child == NULL);
 342                lower_fragcoord(state, intr, var);
 343             } else if (var->data.mode == nir_var_system_value &&
 344                        var->data.location == SYSTEM_VALUE_SAMPLE_POS) {
 345                assert(dvar->deref.child == NULL);
 346                lower_load_sample_pos(state, intr);
 347             }
 348          } else if (intr->intrinsic == nir_intrinsic_load_frag_coord) {
 349             lower_fragcoord(state, intr, NULL);
 350          } else if (intr->intrinsic == nir_intrinsic_load_sample_pos) {
 351             lower_load_sample_pos(state, intr);
 352          } else if (intr->intrinsic == nir_intrinsic_interp_deref_at_offset) {
 353             lower_interp_deref_at_offset(state, intr);
 354          } else if (intr->intrinsic == nir_intrinsic_interp_var_at_offset) {
 355             lower_interp_var_at_offset(state, intr);
 356          }
 357       } else if (instr->type == nir_instr_type_alu) {
 358          nir_alu_instr *alu = nir_instr_as_alu(instr);
 359          if (alu->op == nir_op_fddy ||
 360              alu->op == nir_op_fddy_fine ||
 361              alu->op == nir_op_fddy_coarse)
 362             lower_fddy(state, alu);
 363       }
 364    }
 365 }
 366
 367 static void
 368 lower_wpos_ytransform_impl(lower_wpos_ytransform_state *state, nir_function_impl *impl)
 369 {
 370    nir_builder_init(&state->b, impl);
 371
 372    nir_foreach_block(block, impl) {
 373       lower_wpos_ytransform_block(state, block);
 374    }
 375    nir_metadata_preserve(impl, nir_metadata_block_index |
 376                                nir_metadata_dominance);
 377 }
 378
 379 bool
 380 nir_lower_wpos_ytransform(nir_shader *shader,
 381                           const nir_lower_wpos_ytransform_options *options)
 382 {
 383    lower_wpos_ytransform_state state = {
 384       .options = options,
 385       .shader = shader,
 386    };
 387
 388    assert(shader->info.stage == MESA_SHADER_FRAGMENT);
 389
 390    nir_foreach_function(function, shader) {
 391       if (function->impl)
 392          lower_wpos_ytransform_impl(&state, function->impl);
 393    }
 394
 395    return state.transform != NULL;
 396 }