From 0e97dc25d7736dc4c2a1d8e82cc62b64d003825a Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Date: Wed, 21 Jun 2023 08:29:34 -0400
Subject: [PATCH] pan/mdg: Copy-prop even with swizzle restrictions

Some instructions are not able to swizzle their sources, so we conservatively
refused to propagate moves into them to avoid needing a swizzle on the source.
This is too conservative: we only need to do this if the move swizzles. If there
is only an identity swizzle on the move, we can propagate it without issue. This
will mitigate some instruction count regression from the later modifier
propagation, which will leave lots of moves that need to be propagated.

   total instructions in shared programs: 1514834 -> 1514477 (-0.02%)
   instructions in affected programs: 132297 -> 131940 (-0.27%)
   helped: 349
   HURT: 3
   Instructions are helped.

   total bundles in shared programs: 645093 -> 645069 (<.01%)
   bundles in affected programs: 9650 -> 9626 (-0.25%)
   helped: 42
   HURT: 23
   Bundles are helped.

   total quadwords in shared programs: 1130751 -> 1130469 (-0.02%)
   quadwords in affected programs: 78790 -> 78508 (-0.36%)
   helped: 269
   HURT: 21
   Quadwords are helped.

   total registers in shared programs: 90563 -> 90577 (0.02%)
   registers in affected programs: 163 -> 177 (8.59%)
   helped: 4
   HURT: 16
   Registers are HURT.

   total spills in shared programs: 1400 -> 1399 (-0.07%)
   spills in affected programs: 2 -> 1 (-50.00%)
   helped: 1
   HURT: 0

   total fills in shared programs: 5276 -> 5273 (-0.06%)
   fills in affected programs: 151 -> 148 (-1.99%)
   helped: 1
   HURT: 3

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Italo Nicola <italonicola@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23769>
---
 src/panfrost/midgard/midgard_opt_copy_prop.c | 22 +++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/panfrost/midgard/midgard_opt_copy_prop.c b/src/panfrost/midgard/midgard_opt_copy_prop.c
index 7fa3fa35675..a5c92d19509 100644
--- a/src/panfrost/midgard/midgard_opt_copy_prop.c
+++ b/src/panfrost/midgard/midgard_opt_copy_prop.c
@@ -22,9 +22,25 @@
  * SOFTWARE.
  */
 
+#include "util/bitscan.h"
 #include "compiler.h"
 #include "midgard_ops.h"
 
+static bool
+identity_swizzle(midgard_instruction *mov)
+{
+   /* Write mask should be minimal in SSA form */
+   assert(mir_is_ssa(mov->src[1]));
+   assert(mov->mask == BITFIELD_MASK(util_last_bit(mov->mask)));
+
+   for (unsigned i = 0; i < util_last_bit(mov->mask); ++i) {
+      if (mov->swizzle[1][i] != i)
+         return false;
+   }
+
+   return true;
+}
+
 bool
 midgard_opt_copy_prop(compiler_context *ctx, midgard_block *block)
 {
@@ -65,7 +81,7 @@ midgard_opt_copy_prop(compiler_context *ctx, midgard_block *block)
        * component and even that is restricted. Fragment writeout
        * doesn't even get that much */
 
-      bool skip = false;
+      bool no_swizzle = false;
 
       mir_foreach_instr_global(ctx, q) {
          bool is_tex = q->type == TAG_TEXTURE_4;
@@ -83,13 +99,13 @@ midgard_opt_copy_prop(compiler_context *ctx, midgard_block *block)
 
          mir_foreach_src(q, s) {
             if ((s >= start) && q->src[s] == to) {
-               skip = true;
+               no_swizzle = true;
                break;
             }
          }
       }
 
-      if (skip)
+      if (no_swizzle && !identity_swizzle(ins))
          continue;
 
       if (ctx->blend_src1 == to)