[Mesa-dev] [PATCH 1/2] anv/pipeline: use less instructions for multiview

Caio Marcelo de Oliveira Filho caio.oliveira at intel.com
Tue Feb 27 19:46:50 UTC 2018

The view_index is encoded in the remainder of dividing instance id by
the number of views in the view mask (n). In the general case (handled
by the else clause), there is a need to map from 0..n-1 into the
number of the view being masked. For that a map is encoded.

In the case only the first n bits in the mask are set, the mapping is
trivial, 0..n-1 already represent what view is being referred to.

That case was in the original patch that added
anv_nir_lower_multiview.c but disabled.
 src/intel/vulkan/anv_nir_lower_multiview.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/intel/vulkan/anv_nir_lower_multiview.c b/src/intel/vulkan/anv_nir_lower_multiview.c
index 88e6f9af87..d2aefdee62 100644
--- a/src/intel/vulkan/anv_nir_lower_multiview.c
+++ b/src/intel/vulkan/anv_nir_lower_multiview.c
@@ -86,7 +86,7 @@ build_view_index(struct lower_multiview_state *state)
             nir_umod(b, nir_load_instance_id(b),
                         nir_imm_int(b, _mesa_bitcount(state->view_mask)));
-         if (0 && util_is_power_of_two(state->view_mask + 1)) {
+         if (util_is_power_of_two(state->view_mask + 1)) {
             /* If we have a full view mask, then compacted is what we want */
             state->view_index = compacted;
          } else {

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