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gallium/util: Add u_stream_outputs_for_vertices helper

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This u_prim.h helper determines the number of outputs for stream output,
given a particular primitive type and a vertex count. This is useful for
statically calculating sizes of stream output buffers (i.e. when there
is no geometry/tessellation shader in use).

This helper will be used in Panfrost's transform feedback
implementation, as you can probably guess since why else would I be
submitting it....

See also dEQP's getTransformFeedbackOutputCount routine.

v2: Simplify definition using new helpers, which also extends to non-ES2
primitive types (Eric).

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Alyssa Rosenzweig 2019-08-08 14:27:41 -07:00
parent 8ce4f9bbc3
commit e881aa8c12
1 changed files with 19 additions and 0 deletions
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19
src/gallium/auxiliary/util/u_prim.h
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@ -327,6 +327,25 @@ u_vertices_for_prims(enum pipe_prim_type prim_type, int count)
return info->min + (count - 1) * info->incr;
}
/**
* Returns the number of stream out outputs for a given number of vertices and
* primitive type.
*/
static inline unsigned
u_stream_outputs_for_vertices(enum pipe_prim_type primitive, unsigned nr)
{
/* Extraneous vertices don't contribute to stream outputs */
u_trim_pipe_prim(primitive, &nr);
/* Consider how many primitives are actually generated */
unsigned prims = u_decomposed_prims_for_vertices(primitive, nr);
/* One output per vertex after decomposition */
enum pipe_prim_type base = u_base_prim_type(primitive);
return u_vertices_for_prims(base, prims);
}
const char *u_prim_name(enum pipe_prim_type pipe_prim);