Mesa (main): llvmpipe: fix 4-bit output scaling.

[GitLab Mirror]

Module: Mesa
Branch: main
Commit: 29f4931b520f71b27d65a5df70503d6dfc622aed
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=29f4931b520f71b27d65a5df70503d6dfc622aed

Author: Dave Airlie <airlied at redhat.com>
Date:   Mon Jul 20 15:41:27 2020 +1000

llvmpipe: fix 4-bit output scaling.

This is overkill, but hey 4-bits per channel is hardly something to
care about.

(Suggestions welcome for a better version).

Fixes:
dEQP-GLES2.functional.fbo.render.*rgba4*

Reviewed-by: Adam Jackson <ajax at redhat.com>
Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12001>

---

 src/gallium/drivers/llvmpipe/lp_state_fs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index c77f0f38df8..80dd95f01e9 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -1712,6 +1712,15 @@ scale_bits(struct gallivm_state *gallivm,
       int delta_bits = src_bits - dst_bits;
 
       if (delta_bits <= dst_bits) {
+
+         if (dst_bits == 4) {
+            struct lp_type flt_type = lp_type_float_vec(32, src_type.length * 32);
+
+            result = lp_build_unsigned_norm_to_float(gallivm, src_bits, flt_type, src);
+            result = lp_build_clamped_float_to_unsigned_norm(gallivm, flt_type, dst_bits, result);
+            return result;
+         }
+
          /*
           * Approximate the rescaling with a single shift.
           *