Mesa (master): pan/mdg: Eliminate expand_writemask division

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Module: Mesa
Branch: master
Commit: 28a750c5f2a4b31c4d58165d19c91310b05a26b1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=28a750c5f2a4b31c4d58165d19c91310b05a26b1

Author: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Date:   Thu May 21 18:04:36 2020 -0400

pan/mdg: Eliminate expand_writemask division

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5154>

---

 src/panfrost/midgard/helpers.h      | 6 +++---
 src/panfrost/midgard/midgard_emit.c | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/panfrost/midgard/helpers.h b/src/panfrost/midgard/helpers.h
index 658c43b785d..a7177ce2f2e 100644
--- a/src/panfrost/midgard/helpers.h
+++ b/src/panfrost/midgard/helpers.h
@@ -240,13 +240,13 @@ struct mir_tag_props {
  * which is used for vector units */
 
 static inline unsigned
-expand_writemask(unsigned mask, unsigned channels)
+expand_writemask(unsigned mask, unsigned log2_channels)
 {
         unsigned o = 0;
-        unsigned factor = 8 / channels;
+        unsigned factor = 8 >> log2_channels;
         unsigned expanded = (1 << factor) - 1;
 
-        for (unsigned i = 0; i < channels; ++i)
+        for (unsigned i = 0; i < (1 << log2_channels); ++i)
                 if (mask & (1 << i))
                         o |= (expanded << (factor * i));
 
diff --git a/src/panfrost/midgard/midgard_emit.c b/src/panfrost/midgard/midgard_emit.c
index c8340f9e44d..6431dc02c0e 100644
--- a/src/panfrost/midgard/midgard_emit.c
+++ b/src/panfrost/midgard/midgard_emit.c
@@ -184,9 +184,9 @@ mir_pack_mask_alu(midgard_instruction *ins)
         }
 
         if (ins->alu.reg_mode == midgard_reg_mode_32)
-                ins->alu.mask = expand_writemask(effective, 4);
-        else if (ins->alu.reg_mode == midgard_reg_mode_64)
                 ins->alu.mask = expand_writemask(effective, 2);
+        else if (ins->alu.reg_mode == midgard_reg_mode_64)
+                ins->alu.mask = expand_writemask(effective, 1);
         else
                 ins->alu.mask = effective;
 }