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,
  81                      bool invert, float adjX, float adjY[2])
  82 {
  83    nir_builder *b = &state->b;
  84    nir_variable *fragcoord = intr->variables[0]->var;
  85    nir_ssa_def *wpostrans, *wpos_temp, *wpos_temp_y, *wpos_input;
  86
  87    assert(intr->dest.is_ssa);
  88
  89    b->cursor = nir_before_instr(&intr->instr);
  90
  91    wpostrans = get_transform(state);
  92    wpos_input = nir_load_var(b, fragcoord);
  93
  94    /* First, apply the coordinate shift: */
  95    if (adjX || adjY[0] || adjY[1]) {
  96       if (adjY[0] != adjY[1]) {
  97          /* Adjust the y coordinate by adjY[1] or adjY[0] respectively
  98           * depending on whether inversion is actually going to be applied
  99           * or not, which is determined by testing against the inversion
 100           * state variable used below, which will be either +1 or -1.
 101           */
 102          nir_ssa_def *adj_temp;
 103
 104          adj_temp = nir_cmp(b,
 105                             nir_channel(b, wpostrans, invert ? 2 : 0),
 106                             nir_imm_vec4(b, adjX, adjY[0], 0.0f, 0.0f),
 107                             nir_imm_vec4(b, adjX, adjY[1], 0.0f, 0.0f));
 108
 109          wpos_temp = nir_fadd(b, wpos_input, adj_temp);
 110       } else {
 111          wpos_temp = nir_fadd(b,
 112                               wpos_input,
 113                               nir_imm_vec4(b, adjX, adjY[0], 0.0f, 0.0f));
 114       }
 115       wpos_input = wpos_temp;
 116    } else {
 117       /* MOV wpos_temp, input[wpos]
 118        */
 119       wpos_temp = wpos_input;
 120    }
 121
 122    /* Now the conditional y flip: STATE_FB_WPOS_Y_TRANSFORM.xy/zw will be
 123     * inversion/identity, or the other way around if we're drawing to an FBO.
 124     */
 125    if (invert) {
 126       /* MAD wpos_temp.y, wpos_input, wpostrans.xxxx, wpostrans.yyyy
 127        */
 128       wpos_temp_y = nir_ffma(b,
 129                              nir_channel(b, wpos_temp, 1),
 130                              nir_channel(b, wpostrans, 0),
 131                              nir_channel(b, wpostrans, 1));
 132    } else {
 133       /* MAD wpos_temp.y, wpos_input, wpostrans.zzzz, wpostrans.wwww
 134        */
 135       wpos_temp_y = nir_ffma(b,
 136                              nir_channel(b, wpos_temp, 1),
 137                              nir_channel(b, wpostrans, 2),
 138                              nir_channel(b, wpostrans, 3));
 139    }
 140
 141    wpos_temp = nir_vec4(b,
 142                         nir_channel(b, wpos_temp, 0),
 143                         wpos_temp_y,
 144                         nir_channel(b, wpos_temp, 2),
 145                         nir_channel(b, wpos_temp, 3));
 146
 147    nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(wpos_temp));
 148 }
 149
 150 static void
 151 lower_fragcoord(lower_wpos_ytransform_state *state, nir_intrinsic_instr *intr)
 152 {
 153    const nir_lower_wpos_ytransform_options *options = state->options;
 154    nir_variable *fragcoord = intr->variables[0]->var;
 155    float adjX = 0.0f;
 156    float adjY[2] = { 0.0f, 0.0f };
 157    bool invert = false;
 158
 159    /* Based on logic in emit_wpos():
 160     *
 161     * Query the pixel center conventions supported by the pipe driver and set
 162     * adjX, adjY to help out if it cannot handle the requested one internally.
 163     *
 164     * The bias of the y-coordinate depends on whether y-inversion takes place
 165     * (adjY[1]) or not (adjY[0]), which is in turn dependent on whether we are
 166     * drawing to an FBO (causes additional inversion), and whether the the pipe
 167     * driver origin and the requested origin differ (the latter condition is
 168     * stored in the 'invert' variable).
 169     *
 170     * For height = 100 (i = integer, h = half-integer, l = lower, u = upper):
 171     *
 172     * center shift only:
 173     * i -> h: +0.5
 174     * h -> i: -0.5
 175     *
 176     * inversion only:
 177     * l,i -> u,i: ( 0.0 + 1.0) * -1 + 100 = 99
 178     * l,h -> u,h: ( 0.5 + 0.0) * -1 + 100 = 99.5
 179     * u,i -> l,i: (99.0 + 1.0) * -1 + 100 = 0
 180     * u,h -> l,h: (99.5 + 0.0) * -1 + 100 = 0.5
 181     *
 182     * inversion and center shift:
 183     * l,i -> u,h: ( 0.0 + 0.5) * -1 + 100 = 99.5
 184     * l,h -> u,i: ( 0.5 + 0.5) * -1 + 100 = 99
 185     * u,i -> l,h: (99.0 + 0.5) * -1 + 100 = 0.5
 186     * u,h -> l,i: (99.5 + 0.5) * -1 + 100 = 0
 187     */
 188
 189    if (fragcoord->data.origin_upper_left) {
 190       /* Fragment shader wants origin in upper-left */
 191       if (options->fs_coord_origin_upper_left) {
 192          /* the driver supports upper-left origin */
 193       } else if (options->fs_coord_origin_lower_left) {
 194          /* the driver supports lower-left origin, need to invert Y */
 195          invert = true;
 196       } else {
 197          unreachable("invalid options");
 198       }
 199    } else {
 200       /* Fragment shader wants origin in lower-left */
 201       if (options->fs_coord_origin_lower_left) {
 202          /* the driver supports lower-left origin */
 203       } else if (options->fs_coord_origin_upper_left) {
 204          /* the driver supports upper-left origin, need to invert Y */
 205          invert = true;
 206       } else {
 207          unreachable("invalid options");
 208       }
 209    }
 210
 211    if (fragcoord->data.pixel_center_integer) {
 212       /* Fragment shader wants pixel center integer */
 213       if (options->fs_coord_pixel_center_integer) {
 214          /* the driver supports pixel center integer */
 215          adjY[1] = 1.0f;
 216       } else if (options->fs_coord_pixel_center_half_integer) {
 217          /* the driver supports pixel center half integer, need to bias X,Y */
 218          adjX = -0.5f;
 219          adjY[0] = -0.5f;
 220          adjY[1] = 0.5f;
 221       } else {
 222          unreachable("invalid options");
 223       }
 224    } else {
 225       /* Fragment shader wants pixel center half integer */
 226       if (options->fs_coord_pixel_center_half_integer) {
 227          /* the driver supports pixel center half integer */
 228       } else if (options->fs_coord_pixel_center_integer) {
 229          /* the driver supports pixel center integer, need to bias X,Y */
 230          adjX = adjY[0] = adjY[1] = 0.5f;
 231       } else {
 232          unreachable("invalid options");
 233       }
 234    }
 235
 236    emit_wpos_adjustment(state, intr, invert, adjX, adjY);
 237 }
 238
 239 /* turns 'fddy(p)' into 'fddy(fmul(p, transform.x))' */
 240 static void
 241 lower_fddy(lower_wpos_ytransform_state *state, nir_alu_instr *fddy)
 242 {
 243    nir_builder *b = &state->b;
 244    nir_ssa_def *p, *pt, *trans;
 245
 246    b->cursor = nir_before_instr(&fddy->instr);
 247
 248    p = nir_ssa_for_alu_src(b, fddy, 0);
 249    trans = get_transform(state);
 250    pt = nir_fmul(b, p, nir_channel(b, trans, 0));
 251
 252    nir_instr_rewrite_src(&fddy->instr,
 253                          &fddy->src[0].src,
 254                          nir_src_for_ssa(pt));
 255
 256    for (unsigned i = 0; i < 4; i++)
 257       fddy->src[0].swizzle[i] = MIN2(i, pt->num_components - 1);
 258 }
 259
 260 static bool
 261 lower_wpos_ytransform_block(lower_wpos_ytransform_state *state, nir_block *block)
 262 {
 263    nir_foreach_instr_safe(instr, block) {
 264       if (instr->type == nir_instr_type_intrinsic) {
 265          nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 266          if (intr->intrinsic == nir_intrinsic_load_var) {
 267             nir_deref_var *dvar = intr->variables[0];
 268             nir_variable *var = dvar->var;
 269
 270             if (strcmp(var->name, "gl_FragCoord") == 0) {
 271                /* gl_FragCoord should not have array/struct deref's: */
 272                assert(dvar->deref.child == NULL);
 273                lower_fragcoord(state, intr);
 274             }
 275          }
 276       } else if (instr->type == nir_instr_type_alu) {
 277          nir_alu_instr *alu = nir_instr_as_alu(instr);
 278          if (alu->op == nir_op_fddy)
 279             lower_fddy(state, alu);
 280       }
 281    }
 282
 283    return true;
 284 }
 285
 286 static void
 287 lower_wpos_ytransform_impl(lower_wpos_ytransform_state *state, nir_function_impl *impl)
 288 {
 289    nir_builder_init(&state->b, impl);
 290
 291    nir_foreach_block(block, impl) {
 292       lower_wpos_ytransform_block(state, block);
 293    }
 294    nir_metadata_preserve(impl, nir_metadata_block_index |
 295                                nir_metadata_dominance);
 296 }
 297
 298 bool
 299 nir_lower_wpos_ytransform(nir_shader *shader,
 300                           const nir_lower_wpos_ytransform_options *options)
 301 {
 302    lower_wpos_ytransform_state state = {
 303       .options = options,
 304       .shader = shader,
 305    };
 306
 307    assert(shader->stage == MESA_SHADER_FRAGMENT);
 308
 309    nir_foreach_function(function, shader) {
 310       if (function->impl)
 311          lower_wpos_ytransform_impl(&state, function->impl);
 312    }
 313
 314    return state.transform != NULL;
 315 }