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      1 /*
      2  * Copyright  2015 Intel Corporation
      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
     20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
     21  * IN THE SOFTWARE.
     22  */
     23 
     24 #include "nir.h"
     25 #include "nir_builder.h"
     26 
     27 static nir_intrinsic_instr *
     28 as_intrinsic(nir_instr *instr, nir_intrinsic_op op)
     29 {
     30    if (instr->type != nir_instr_type_intrinsic)
     31       return NULL;
     32 
     33    nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
     34    if (intrin->intrinsic != op)
     35       return NULL;
     36 
     37    return intrin;
     38 }
     39 
     40 static nir_intrinsic_instr *
     41 as_set_vertex_count(nir_instr *instr)
     42 {
     43    return as_intrinsic(instr, nir_intrinsic_set_vertex_count);
     44 }
     45 
     46 /**
     47  * If a geometry shader emits a constant number of vertices, return the
     48  * number of vertices.  Otherwise, return -1 (unknown).
     49  *
     50  * This only works if you've used nir_lower_gs_intrinsics() to do vertex
     51  * counting at the NIR level.
     52  */
     53 int
     54 nir_gs_count_vertices(const nir_shader *shader)
     55 {
     56    int count = -1;
     57 
     58    nir_foreach_function(function, shader) {
     59       if (!function->impl)
     60          continue;
     61 
     62       /* set_vertex_count intrinsics only appear in predecessors of the
     63        * end block.  So we don't need to walk all of them.
     64        */
     65       struct set_entry *entry;
     66       set_foreach(function->impl->end_block->predecessors, entry) {
     67          nir_block *block = (nir_block *) entry->key;
     68 
     69          nir_foreach_instr_reverse(instr, block) {
     70             nir_intrinsic_instr *intrin = as_set_vertex_count(instr);
     71             if (!intrin)
     72                continue;
     73 
     74             nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
     75             /* We've found a non-constant value.  Bail. */
     76             if (!val)
     77                return -1;
     78 
     79             if (count == -1)
     80                count = val->i32[0];
     81 
     82             /* We've found contradictory set_vertex_count intrinsics.
     83              * This can happen if there are early-returns in main() and
     84              * different paths emit different numbers of vertices.
     85              */
     86             if (count != val->i32[0])
     87                return -1;
     88          }
     89       }
     90    }
     91 
     92    return count;
     93 }
     94