gallium/util: add a helper to compute vertex count from primitive count

v2:
  - Only compute vertex counts for base primitives.
  - Add a unit test (Eric)

Reviewed-by: Eric Anholt <eric@anholt.net>

2 files changed, 47 insertions, 1 deletions

diff --git a/src/gallium/tests/unit/meson.build b/src/gallium/tests/unit/meson.build
index d4f3aed0877..afde9840c37 100644
--- a/src/gallium/tests/unit/meson.build
+++ b/src/gallium/tests/unit/meson.build
@@ -19,7 +19,8 @@
 # SOFTWARE.
 
 foreach t : ['pipe_barrier_test', 'u_cache_test', 'u_half_test',
-             'u_format_test', 'u_format_compatible_test', 'translate_test']
+             'u_format_test', 'u_format_compatible_test', 'translate_test',
+             'u_prim_verts_test' ]
   exe = executable(
     t,
     '@0@.c'.format(t),
diff --git a/src/gallium/tests/unit/u_prim_verts_test.c b/src/gallium/tests/unit/u_prim_verts_test.c
new file mode 100644
index 00000000000..94b64f75eec
--- /dev/null
+++ b/src/gallium/tests/unit/u_prim_verts_test.c
@@ -0,0 +1,45 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "util/u_prim.h"
+
+struct test_info {
+   enum pipe_prim_type prim_type;
+   uint32_t count;
+   uint32_t expected;
+};
+
+struct test_info tests[] = {
+   { PIPE_PRIM_POINTS, 0, 0 },
+   { PIPE_PRIM_POINTS, 1, 1 },
+   { PIPE_PRIM_POINTS, 2, 2 },
+
+   { PIPE_PRIM_LINES, 0, 0 },
+   { PIPE_PRIM_LINES, 1, 2 },
+   { PIPE_PRIM_LINES, 2, 4 },
+
+   { PIPE_PRIM_TRIANGLES, 0, 0 },
+   { PIPE_PRIM_TRIANGLES, 1, 3 },
+   { PIPE_PRIM_TRIANGLES, 2, 6 },
+
+   { PIPE_PRIM_QUADS, 0, 0 },
+   { PIPE_PRIM_QUADS, 1, 4 },
+   { PIPE_PRIM_QUADS, 2, 8 },
+};
+
+int
+main(int argc, char **argv)
+{
+   for(int i = 0; i < ARRAY_SIZE(tests); i++) {
+      struct test_info *info = &tests[i];
+      uint32_t n = u_vertices_for_prims(info->prim_type, info->count);
+      if (n != info->expected) {
+         printf("Failure! Expected %u vertices for %u x %s, but got %u.\n",
+                info->expected, info->count, u_prim_name(info->prim_type), n);
+         return 1;
+      }
+   }
+
+   printf("Success!\n");
+   return 0;
+}