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1 /**************************************************************************
2  *
3  * Copyright 2007 VMware, Inc.
4  * All Rights Reserved.
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a
7  * copy of this software and associated documentation files (the
8  * "Software"), to deal in the Software without restriction, including
9  * without limitation the rights to use, copy, modify, merge, publish,
10  * distribute, sub license, and/or sell copies of the Software, and to
11  * permit persons to whom the Software is furnished to do so, subject to
12  * the following conditions:
13  *
14  * The above copyright notice and this permission notice (including the
15  * next paragraph) shall be included in all copies or substantial portions
16  * of the Software.
17  *
18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21  * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25  *
26  **************************************************************************/
27 
28 /*
29  * Binning code for lines
30  */
31 
32 #include "util/u_math.h"
33 #include "util/u_memory.h"
34 #include "lp_perf.h"
35 #include "lp_setup_context.h"
36 #include "lp_rast.h"
37 #include "lp_state_fs.h"
38 #include "lp_state_setup.h"
39 #include "lp_context.h"
40 #include "draw/draw_context.h"
41 
42 #define NUM_CHANNELS 4
43 
44 struct lp_line_info {
45 
46    float dx;
47    float dy;
48    float oneoverarea;
49    boolean frontfacing;
50 
51    const float (*v1)[4];
52    const float (*v2)[4];
53 
54    float (*a0)[4];
55    float (*dadx)[4];
56    float (*dady)[4];
57 };
58 
59 
60 /**
61  * Compute a0 for a constant-valued coefficient (GL_FLAT shading).
62  */
constant_coef(struct lp_setup_context * setup,struct lp_line_info * info,unsigned slot,const float value,unsigned i)63 static void constant_coef( struct lp_setup_context *setup,
64                            struct lp_line_info *info,
65                            unsigned slot,
66                            const float value,
67                            unsigned i )
68 {
69    info->a0[slot][i] = value;
70    info->dadx[slot][i] = 0.0f;
71    info->dady[slot][i] = 0.0f;
72 }
73 
74 
75 /**
76  * Compute a0, dadx and dady for a linearly interpolated coefficient,
77  * for a triangle.
78  */
linear_coef(struct lp_setup_context * setup,struct lp_line_info * info,unsigned slot,unsigned vert_attr,unsigned i)79 static void linear_coef( struct lp_setup_context *setup,
80                          struct lp_line_info *info,
81                          unsigned slot,
82                          unsigned vert_attr,
83                          unsigned i)
84 {
85    float a1 = info->v1[vert_attr][i];
86    float a2 = info->v2[vert_attr][i];
87 
88    float da21 = a1 - a2;
89    float dadx = da21 * info->dx * info->oneoverarea;
90    float dady = da21 * info->dy * info->oneoverarea;
91 
92    info->dadx[slot][i] = dadx;
93    info->dady[slot][i] = dady;
94 
95    info->a0[slot][i] = (a1 -
96                               (dadx * (info->v1[0][0] - setup->pixel_offset) +
97                                dady * (info->v1[0][1] - setup->pixel_offset)));
98 }
99 
100 
101 /**
102  * Compute a0, dadx and dady for a perspective-corrected interpolant,
103  * for a triangle.
104  * We basically multiply the vertex value by 1/w before computing
105  * the plane coefficients (a0, dadx, dady).
106  * Later, when we compute the value at a particular fragment position we'll
107  * divide the interpolated value by the interpolated W at that fragment.
108  */
perspective_coef(struct lp_setup_context * setup,struct lp_line_info * info,unsigned slot,unsigned vert_attr,unsigned i)109 static void perspective_coef( struct lp_setup_context *setup,
110                               struct lp_line_info *info,
111                               unsigned slot,
112                               unsigned vert_attr,
113                               unsigned i)
114 {
115    /* premultiply by 1/w  (v[0][3] is always 1/w):
116     */
117    float a1 = info->v1[vert_attr][i] * info->v1[0][3];
118    float a2 = info->v2[vert_attr][i] * info->v2[0][3];
119 
120    float da21 = a1 - a2;
121    float dadx = da21 * info->dx * info->oneoverarea;
122    float dady = da21 * info->dy * info->oneoverarea;
123 
124    info->dadx[slot][i] = dadx;
125    info->dady[slot][i] = dady;
126 
127    info->a0[slot][i] = (a1 -
128                         (dadx * (info->v1[0][0] - setup->pixel_offset) +
129                          dady * (info->v1[0][1] - setup->pixel_offset)));
130 }
131 
132 static void
setup_fragcoord_coef(struct lp_setup_context * setup,struct lp_line_info * info,unsigned slot,unsigned usage_mask)133 setup_fragcoord_coef( struct lp_setup_context *setup,
134                       struct lp_line_info *info,
135                       unsigned slot,
136                       unsigned usage_mask)
137 {
138    /*X*/
139    if (usage_mask & TGSI_WRITEMASK_X) {
140       info->a0[slot][0] = 0.0;
141       info->dadx[slot][0] = 1.0;
142       info->dady[slot][0] = 0.0;
143    }
144 
145    /*Y*/
146    if (usage_mask & TGSI_WRITEMASK_Y) {
147       info->a0[slot][1] = 0.0;
148       info->dadx[slot][1] = 0.0;
149       info->dady[slot][1] = 1.0;
150    }
151 
152    /*Z*/
153    if (usage_mask & TGSI_WRITEMASK_Z) {
154       linear_coef(setup, info, slot, 0, 2);
155    }
156 
157    /*W*/
158    if (usage_mask & TGSI_WRITEMASK_W) {
159       linear_coef(setup, info, slot, 0, 3);
160    }
161 }
162 
163 /**
164  * Compute the tri->coef[] array dadx, dady, a0 values.
165  */
setup_line_coefficients(struct lp_setup_context * setup,struct lp_line_info * info)166 static void setup_line_coefficients( struct lp_setup_context *setup,
167                                      struct lp_line_info *info)
168 {
169    const struct lp_setup_variant_key *key = &setup->setup.variant->key;
170    unsigned fragcoord_usage_mask = TGSI_WRITEMASK_XYZ;
171    unsigned slot;
172 
173    /* setup interpolation for all the remaining attributes:
174     */
175    for (slot = 0; slot < key->num_inputs; slot++) {
176       unsigned vert_attr = key->inputs[slot].src_index;
177       unsigned usage_mask = key->inputs[slot].usage_mask;
178       unsigned i;
179 
180       switch (key->inputs[slot].interp) {
181       case LP_INTERP_CONSTANT:
182          if (key->flatshade_first) {
183             for (i = 0; i < NUM_CHANNELS; i++)
184                if (usage_mask & (1 << i))
185                   constant_coef(setup, info, slot+1, info->v1[vert_attr][i], i);
186          }
187          else {
188             for (i = 0; i < NUM_CHANNELS; i++)
189                if (usage_mask & (1 << i))
190                   constant_coef(setup, info, slot+1, info->v2[vert_attr][i], i);
191          }
192          break;
193 
194       case LP_INTERP_LINEAR:
195          for (i = 0; i < NUM_CHANNELS; i++)
196             if (usage_mask & (1 << i))
197                linear_coef(setup, info, slot+1, vert_attr, i);
198          break;
199 
200       case LP_INTERP_PERSPECTIVE:
201          for (i = 0; i < NUM_CHANNELS; i++)
202             if (usage_mask & (1 << i))
203                perspective_coef(setup, info, slot+1, vert_attr, i);
204          fragcoord_usage_mask |= TGSI_WRITEMASK_W;
205          break;
206 
207       case LP_INTERP_POSITION:
208          /*
209           * The generated pixel interpolators will pick up the coeffs from
210           * slot 0, so all need to ensure that the usage mask is covers all
211           * usages.
212           */
213          fragcoord_usage_mask |= usage_mask;
214          break;
215 
216       case LP_INTERP_FACING:
217          for (i = 0; i < NUM_CHANNELS; i++)
218             if (usage_mask & (1 << i))
219                constant_coef(setup, info, slot+1,
220                              info->frontfacing ? 1.0f : -1.0f, i);
221          break;
222 
223       default:
224          assert(0);
225       }
226    }
227 
228    /* The internal position input is in slot zero:
229     */
230    setup_fragcoord_coef(setup, info, 0,
231                         fragcoord_usage_mask);
232 }
233 
234 
235 
subpixel_snap(float a)236 static inline int subpixel_snap( float a )
237 {
238    return util_iround(FIXED_ONE * a);
239 }
240 
241 
242 /**
243  * Print line vertex attribs (for debug).
244  */
245 static void
print_line(struct lp_setup_context * setup,const float (* v1)[4],const float (* v2)[4])246 print_line(struct lp_setup_context *setup,
247            const float (*v1)[4],
248            const float (*v2)[4])
249 {
250    const struct lp_setup_variant_key *key = &setup->setup.variant->key;
251    uint i;
252 
253    debug_printf("llvmpipe line\n");
254    for (i = 0; i < 1 + key->num_inputs; i++) {
255       debug_printf("  v1[%d]:  %f %f %f %f\n", i,
256                    v1[i][0], v1[i][1], v1[i][2], v1[i][3]);
257    }
258    for (i = 0; i < 1 + key->num_inputs; i++) {
259       debug_printf("  v2[%d]:  %f %f %f %f\n", i,
260                    v2[i][0], v2[i][1], v2[i][2], v2[i][3]);
261    }
262 }
263 
264 
sign(float x)265 static inline boolean sign(float x){
266    return x >= 0;
267 }
268 
269 
270 /* Used on positive floats only:
271  */
fracf(float f)272 static inline float fracf(float f)
273 {
274    return f - floorf(f);
275 }
276 
277 
278 
279 static boolean
try_setup_line(struct lp_setup_context * setup,const float (* v1)[4],const float (* v2)[4])280 try_setup_line( struct lp_setup_context *setup,
281                const float (*v1)[4],
282                const float (*v2)[4])
283 {
284    struct llvmpipe_context *lp_context = (struct llvmpipe_context *)setup->pipe;
285    struct lp_scene *scene = setup->scene;
286    const struct lp_setup_variant_key *key = &setup->setup.variant->key;
287    struct lp_rast_triangle *line;
288    struct lp_rast_plane *plane;
289    struct lp_line_info info;
290    float width = MAX2(1.0, setup->line_width);
291    const struct u_rect *scissor;
292    struct u_rect bbox, bboxpos;
293    boolean s_planes[4];
294    unsigned tri_bytes;
295    int x[4];
296    int y[4];
297    int i;
298    int nr_planes = 4;
299    unsigned viewport_index = 0;
300    unsigned layer = 0;
301    float pixel_offset = setup->multisample ? 0.0 : setup->pixel_offset;
302    /* linewidth should be interpreted as integer */
303    int fixed_width = util_iround(width) * FIXED_ONE;
304 
305    float x_offset=0;
306    float y_offset=0;
307    float x_offset_end=0;
308    float y_offset_end=0;
309 
310    float x1diff;
311    float y1diff;
312    float x2diff;
313    float y2diff;
314    float dx, dy;
315    float area;
316    const float (*pv)[4];
317 
318    boolean draw_start;
319    boolean draw_end;
320    boolean will_draw_start;
321    boolean will_draw_end;
322 
323    if (lp_context->active_statistics_queries) {
324       lp_context->pipeline_statistics.c_primitives++;
325    }
326 
327    if (0)
328       print_line(setup, v1, v2);
329 
330    if (setup->flatshade_first) {
331       pv = v1;
332    }
333    else {
334       pv = v2;
335    }
336    if (setup->viewport_index_slot > 0) {
337       unsigned *udata = (unsigned*)pv[setup->viewport_index_slot];
338       viewport_index = lp_clamp_viewport_idx(*udata);
339    }
340    if (setup->layer_slot > 0) {
341       layer = *(unsigned*)pv[setup->layer_slot];
342       layer = MIN2(layer, scene->fb_max_layer);
343    }
344 
345    dx = v1[0][0] - v2[0][0];
346    dy = v1[0][1] - v2[0][1];
347    area = (dx * dx  + dy * dy);
348    if (area == 0) {
349       LP_COUNT(nr_culled_tris);
350       return TRUE;
351    }
352 
353    info.oneoverarea = 1.0f / area;
354    info.dx = dx;
355    info.dy = dy;
356    info.v1 = v1;
357    info.v2 = v2;
358 
359 
360    /* X-MAJOR LINE */
361    if (fabsf(dx) >= fabsf(dy)) {
362       float dydx = dy / dx;
363 
364       x1diff = v1[0][0] - floorf(v1[0][0]) - 0.5f;
365       y1diff = v1[0][1] - floorf(v1[0][1]) - 0.5f;
366       x2diff = v2[0][0] - floorf(v2[0][0]) - 0.5f;
367       y2diff = v2[0][1] - floorf(v2[0][1]) - 0.5f;
368 
369       if (y2diff==-0.5 && dy<0){
370          y2diff = 0.5;
371       }
372 
373       /*
374        * Diamond exit rule test for starting point
375        */
376       if (fabsf(x1diff) + fabsf(y1diff) < 0.5) {
377          draw_start = TRUE;
378       }
379       else if (sign(x1diff) == sign(-dx)) {
380          draw_start = FALSE;
381       }
382       else if (sign(-y1diff) != sign(dy)) {
383          draw_start = TRUE;
384       }
385       else {
386          /* do intersection test */
387          float yintersect = fracf(v1[0][1]) + x1diff * dydx;
388          draw_start = (yintersect < 1.0 && yintersect > 0.0);
389       }
390 
391 
392       /*
393        * Diamond exit rule test for ending point
394        */
395       if (fabsf(x2diff) + fabsf(y2diff) < 0.5) {
396          draw_end = FALSE;
397       }
398       else if (sign(x2diff) != sign(-dx)) {
399          draw_end = FALSE;
400       }
401       else if (sign(-y2diff) == sign(dy)) {
402          draw_end = TRUE;
403       }
404       else {
405          /* do intersection test */
406          float yintersect = fracf(v2[0][1]) + x2diff * dydx;
407          draw_end = (yintersect < 1.0 && yintersect > 0.0);
408       }
409 
410       /* Are we already drawing start/end?
411        */
412       will_draw_start = sign(-x1diff) != sign(dx);
413       will_draw_end = (sign(x2diff) == sign(-dx)) || x2diff==0;
414 
415       if (dx < 0) {
416          /* if v2 is to the right of v1, swap pointers */
417          const float (*temp)[4] = v1;
418          v1 = v2;
419          v2 = temp;
420          dx = -dx;
421          dy = -dy;
422          /* Otherwise shift planes appropriately */
423          if (will_draw_start != draw_start) {
424             x_offset_end = - x1diff - 0.5;
425             y_offset_end = x_offset_end * dydx;
426 
427          }
428          if (will_draw_end != draw_end) {
429             x_offset = - x2diff - 0.5;
430             y_offset = x_offset * dydx;
431          }
432 
433       }
434       else{
435          /* Otherwise shift planes appropriately */
436          if (will_draw_start != draw_start) {
437             x_offset = - x1diff + 0.5;
438             y_offset = x_offset * dydx;
439          }
440          if (will_draw_end != draw_end) {
441             x_offset_end = - x2diff + 0.5;
442             y_offset_end = x_offset_end * dydx;
443          }
444       }
445 
446       /* x/y positions in fixed point */
447       x[0] = subpixel_snap(v1[0][0] + x_offset     - pixel_offset);
448       x[1] = subpixel_snap(v2[0][0] + x_offset_end - pixel_offset);
449       x[2] = subpixel_snap(v2[0][0] + x_offset_end - pixel_offset);
450       x[3] = subpixel_snap(v1[0][0] + x_offset     - pixel_offset);
451 
452       y[0] = subpixel_snap(v1[0][1] + y_offset     - pixel_offset) - fixed_width/2;
453       y[1] = subpixel_snap(v2[0][1] + y_offset_end - pixel_offset) - fixed_width/2;
454       y[2] = subpixel_snap(v2[0][1] + y_offset_end - pixel_offset) + fixed_width/2;
455       y[3] = subpixel_snap(v1[0][1] + y_offset     - pixel_offset) + fixed_width/2;
456 
457    }
458    else {
459       const float dxdy = dx / dy;
460 
461       /* Y-MAJOR LINE */
462       x1diff = v1[0][0] - floorf(v1[0][0]) - 0.5f;
463       y1diff = v1[0][1] - floorf(v1[0][1]) - 0.5f;
464       x2diff = v2[0][0] - floorf(v2[0][0]) - 0.5f;
465       y2diff = v2[0][1] - floorf(v2[0][1]) - 0.5f;
466 
467       if (x2diff==-0.5 && dx<0) {
468          x2diff = 0.5;
469       }
470 
471       /*
472        * Diamond exit rule test for starting point
473        */
474       if (fabsf(x1diff) + fabsf(y1diff) < 0.5) {
475          draw_start = TRUE;
476       }
477       else if (sign(-y1diff) == sign(dy)) {
478          draw_start = FALSE;
479       }
480       else if (sign(x1diff) != sign(-dx)) {
481          draw_start = TRUE;
482       }
483       else {
484          /* do intersection test */
485          float xintersect = fracf(v1[0][0]) + y1diff * dxdy;
486          draw_start = (xintersect < 1.0 && xintersect > 0.0);
487       }
488 
489       /*
490        * Diamond exit rule test for ending point
491        */
492       if (fabsf(x2diff) + fabsf(y2diff) < 0.5) {
493          draw_end = FALSE;
494       }
495       else if (sign(-y2diff) != sign(dy) ) {
496          draw_end = FALSE;
497       }
498       else if (sign(x2diff) == sign(-dx) ) {
499          draw_end = TRUE;
500       }
501       else {
502          /* do intersection test */
503          float xintersect = fracf(v2[0][0]) + y2diff * dxdy;
504          draw_end = (xintersect < 1.0 && xintersect >= 0.0);
505       }
506 
507       /* Are we already drawing start/end?
508        */
509       will_draw_start = sign(y1diff) == sign(dy);
510       will_draw_end = (sign(-y2diff) == sign(dy)) || y2diff==0;
511 
512       if (dy > 0) {
513          /* if v2 is on top of v1, swap pointers */
514          const float (*temp)[4] = v1;
515          v1 = v2;
516          v2 = temp;
517          dx = -dx;
518          dy = -dy;
519 
520          /* Otherwise shift planes appropriately */
521          if (will_draw_start != draw_start) {
522             y_offset_end = - y1diff + 0.5;
523             x_offset_end = y_offset_end * dxdy;
524          }
525          if (will_draw_end != draw_end) {
526             y_offset = - y2diff + 0.5;
527             x_offset = y_offset * dxdy;
528          }
529       }
530       else {
531          /* Otherwise shift planes appropriately */
532          if (will_draw_start != draw_start) {
533             y_offset = - y1diff - 0.5;
534             x_offset = y_offset * dxdy;
535 
536          }
537          if (will_draw_end != draw_end) {
538             y_offset_end = - y2diff - 0.5;
539             x_offset_end = y_offset_end * dxdy;
540          }
541       }
542 
543       /* x/y positions in fixed point */
544       x[0] = subpixel_snap(v1[0][0] + x_offset     - pixel_offset) - fixed_width/2;
545       x[1] = subpixel_snap(v2[0][0] + x_offset_end - pixel_offset) - fixed_width/2;
546       x[2] = subpixel_snap(v2[0][0] + x_offset_end - pixel_offset) + fixed_width/2;
547       x[3] = subpixel_snap(v1[0][0] + x_offset     - pixel_offset) + fixed_width/2;
548 
549       y[0] = subpixel_snap(v1[0][1] + y_offset     - pixel_offset);
550       y[1] = subpixel_snap(v2[0][1] + y_offset_end - pixel_offset);
551       y[2] = subpixel_snap(v2[0][1] + y_offset_end - pixel_offset);
552       y[3] = subpixel_snap(v1[0][1] + y_offset     - pixel_offset);
553    }
554 
555    /* Bounding rectangle (in pixels) */
556    {
557       /* Yes this is necessary to accurately calculate bounding boxes
558        * with the two fill-conventions we support.  GL (normally) ends
559        * up needing a bottom-left fill convention, which requires
560        * slightly different rounding.
561        */
562       int adj = (setup->bottom_edge_rule != 0) ? 1 : 0;
563 
564       bbox.x0 = (MIN4(x[0], x[1], x[2], x[3]) + (FIXED_ONE-1)) >> FIXED_ORDER;
565       bbox.x1 = (MAX4(x[0], x[1], x[2], x[3]) + (FIXED_ONE-1)) >> FIXED_ORDER;
566       bbox.y0 = (MIN4(y[0], y[1], y[2], y[3]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
567       bbox.y1 = (MAX4(y[0], y[1], y[2], y[3]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
568 
569       /* Inclusive coordinates:
570        */
571       bbox.x1--;
572       bbox.y1--;
573    }
574 
575    if (bbox.x1 < bbox.x0 ||
576        bbox.y1 < bbox.y0) {
577       if (0) debug_printf("empty bounding box\n");
578       LP_COUNT(nr_culled_tris);
579       return TRUE;
580    }
581 
582    if (!u_rect_test_intersection(&setup->draw_regions[viewport_index], &bbox)) {
583       if (0) debug_printf("offscreen\n");
584       LP_COUNT(nr_culled_tris);
585       return TRUE;
586    }
587 
588    bboxpos = bbox;
589 
590    /* Can safely discard negative regions:
591     */
592    bboxpos.x0 = MAX2(bboxpos.x0, 0);
593    bboxpos.y0 = MAX2(bboxpos.y0, 0);
594 
595    nr_planes = 4;
596    /*
597     * Determine how many scissor planes we need, that is drop scissor
598     * edges if the bounding box of the tri is fully inside that edge.
599     */
600    scissor = &setup->draw_regions[viewport_index];
601    scissor_planes_needed(s_planes, &bboxpos, scissor);
602    nr_planes += s_planes[0] + s_planes[1] + s_planes[2] + s_planes[3];
603 
604    line = lp_setup_alloc_triangle(scene,
605                                   key->num_inputs,
606                                   nr_planes,
607                                   &tri_bytes);
608    if (!line)
609       return FALSE;
610 
611 #ifdef DEBUG
612    line->v[0][0] = v1[0][0];
613    line->v[1][0] = v2[0][0];
614    line->v[0][1] = v1[0][1];
615    line->v[1][1] = v2[0][1];
616 #endif
617 
618    LP_COUNT(nr_tris);
619 
620    /* calculate the deltas */
621    plane = GET_PLANES(line);
622    plane[0].dcdy = x[0] - x[1];
623    plane[1].dcdy = x[1] - x[2];
624    plane[2].dcdy = x[2] - x[3];
625    plane[3].dcdy = x[3] - x[0];
626 
627    plane[0].dcdx = y[0] - y[1];
628    plane[1].dcdx = y[1] - y[2];
629    plane[2].dcdx = y[2] - y[3];
630    plane[3].dcdx = y[3] - y[0];
631 
632    if (draw_will_inject_frontface(lp_context->draw) &&
633        setup->face_slot > 0) {
634       line->inputs.frontfacing = v1[setup->face_slot][0];
635    } else {
636       line->inputs.frontfacing = TRUE;
637    }
638 
639    /* Setup parameter interpolants:
640     */
641    info.a0 = GET_A0(&line->inputs);
642    info.dadx = GET_DADX(&line->inputs);
643    info.dady = GET_DADY(&line->inputs);
644    info.frontfacing = line->inputs.frontfacing;
645    setup_line_coefficients(setup, &info);
646 
647    line->inputs.disable = FALSE;
648    line->inputs.opaque = FALSE;
649    line->inputs.layer = layer;
650    line->inputs.viewport_index = viewport_index;
651 
652    /*
653     * XXX: this code is mostly identical to the one in lp_setup_tri, except it
654     * uses 4 planes instead of 3. Could share the code (including the sse
655     * assembly, in fact we'd get the 4th plane for free).
656     * The only difference apart from storing the 4th plane would be some
657     * different shuffle for calculating dcdx/dcdy.
658     */
659    for (i = 0; i < 4; i++) {
660 
661       /* half-edge constants, will be iterated over the whole render
662        * target.
663        */
664       plane[i].c = IMUL64(plane[i].dcdx, x[i]) - IMUL64(plane[i].dcdy, y[i]);
665 
666       /* correct for top-left vs. bottom-left fill convention.
667        */
668       if (plane[i].dcdx < 0) {
669          /* both fill conventions want this - adjust for left edges */
670          plane[i].c++;
671       }
672       else if (plane[i].dcdx == 0) {
673          if (pixel_offset == 0) {
674             /* correct for top-left fill convention:
675              */
676             if (plane[i].dcdy > 0) plane[i].c++;
677          }
678          else {
679             /* correct for bottom-left fill convention:
680              */
681             if (plane[i].dcdy < 0) plane[i].c++;
682          }
683       }
684 
685       plane[i].dcdx *= FIXED_ONE;
686       plane[i].dcdy *= FIXED_ONE;
687 
688       /* find trivial reject offsets for each edge for a single-pixel
689        * sized block.  These will be scaled up at each recursive level to
690        * match the active blocksize.  Scaling in this way works best if
691        * the blocks are square.
692        */
693       plane[i].eo = 0;
694       if (plane[i].dcdx < 0) plane[i].eo -= plane[i].dcdx;
695       if (plane[i].dcdy > 0) plane[i].eo += plane[i].dcdy;
696    }
697 
698 
699    /*
700     * When rasterizing scissored tris, use the intersection of the
701     * triangle bounding box and the scissor rect to generate the
702     * scissor planes.
703     *
704     * This permits us to cut off the triangle "tails" that are present
705     * in the intermediate recursive levels caused when two of the
706     * triangles edges don't diverge quickly enough to trivially reject
707     * exterior blocks from the triangle.
708     *
709     * It's not really clear if it's worth worrying about these tails,
710     * but since we generate the planes for each scissored tri, it's
711     * free to trim them in this case.
712     *
713     * Note that otherwise, the scissor planes only vary in 'C' value,
714     * and even then only on state-changes.  Could alternatively store
715     * these planes elsewhere.
716     * (Or only store the c value together with a bit indicating which
717     * scissor edge this is, so rasterization would treat them differently
718     * (easier to evaluate) to ordinary planes.)
719     */
720    if (nr_planes > 4) {
721       struct lp_rast_plane *plane_s = &plane[4];
722 
723       if (s_planes[0]) {
724          plane_s->dcdx = ~0U << 8;
725          plane_s->dcdy = 0;
726          plane_s->c = (1-scissor->x0) << 8;
727          plane_s->eo = 1 << 8;
728          plane_s++;
729       }
730       if (s_planes[1]) {
731          plane_s->dcdx = 1 << 8;
732          plane_s->dcdy = 0;
733          plane_s->c = (scissor->x1+1) << 8;
734          plane_s->eo = 0 << 8;
735          plane_s++;
736       }
737       if (s_planes[2]) {
738          plane_s->dcdx = 0;
739          plane_s->dcdy = 1 << 8;
740          plane_s->c = (1-scissor->y0) << 8;
741          plane_s->eo = 1 << 8;
742          plane_s++;
743       }
744       if (s_planes[3]) {
745          plane_s->dcdx = 0;
746          plane_s->dcdy = ~0U << 8;
747          plane_s->c = (scissor->y1+1) << 8;
748          plane_s->eo = 0;
749          plane_s++;
750       }
751       assert(plane_s == &plane[nr_planes]);
752    }
753 
754    return lp_setup_bin_triangle(setup, line, &bbox, &bboxpos, nr_planes, viewport_index);
755 }
756 
757 
lp_setup_line_discard(struct lp_setup_context * setup,const float (* v0)[4],const float (* v1)[4])758 static void lp_setup_line_discard(struct lp_setup_context *setup,
759                                   const float (*v0)[4],
760                                   const float (*v1)[4])
761 {
762 }
763 
lp_setup_line(struct lp_setup_context * setup,const float (* v0)[4],const float (* v1)[4])764 static void lp_setup_line(struct lp_setup_context *setup,
765                           const float (*v0)[4],
766                           const float (*v1)[4])
767 {
768    if (!try_setup_line(setup, v0, v1)) {
769       if (!lp_setup_flush_and_restart(setup))
770          return;
771 
772       if (!try_setup_line(setup, v0, v1))
773          return;
774    }
775 }
776 
777 
lp_setup_choose_line(struct lp_setup_context * setup)778 void lp_setup_choose_line(struct lp_setup_context *setup)
779 {
780    if (setup->rasterizer_discard) {
781       setup->line = lp_setup_line_discard;
782    } else {
783       setup->line = lp_setup_line;
784    }
785 }
786 
787 
788