agx: Handle uniforms passed to COLLECT

It's useful to be able to copyprop uniform registers into COLLECT. That
requires handling of uniform registers in the parallel copy lowering,
which isn't too hard to add.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18813>

src/asahi/compiler/agx_compiler.h

@@ -769,8 +769,9 @@ struct agx_copy {
    /* Base register destination of the copy */
    unsigned dest;
 
-   /* Base register source of the copy */
+   /* Base register source (or uniform base) of the copy */
    unsigned src;
+   bool is_uniform;
 
    /* Size of the copy */
    enum agx_size size;

src/asahi/compiler/agx_lower_parallel_copy.c

@@ -40,22 +40,31 @@
  * We only handles register-register copies, not general agx_index sources. This
  * suffices for its internal use for register allocation.
  */
+static agx_index
+copy_src(const struct agx_copy *copy)
+{
+   if (copy->is_uniform)
+      return agx_uniform(copy->src, copy->size);
+   else
+      return agx_register(copy->src, copy->size);
+}
 
 static void
 do_copy(agx_builder *b, const struct agx_copy *copy)
 {
-   agx_mov_to(b, agx_register(copy->dest, copy->size),
-                 agx_register(copy->src, copy->size));
+   agx_mov_to(b, agx_register(copy->dest, copy->size), copy_src(copy));
 }
 
 static void
 do_swap(agx_builder *b, const struct agx_copy *copy)
 {
+   assert(!copy->is_uniform && "cannot swap uniform with GPR");
+
    if (copy->dest == copy->src)
       return;
 
    agx_index x = agx_register(copy->dest, copy->size);
-   agx_index y = agx_register(copy->src, copy->size);
+   agx_index y = copy_src(copy);
 
    agx_xor_to(b, x, x, y);
    agx_xor_to(b, y, x, y);
@@ -92,8 +101,7 @@ entry_blocked(struct agx_copy *entry, struct copy_ctx *ctx)
 static bool
 is_real(struct agx_copy *entry)
 {
-   /* TODO: Allow immediates in agx_copy */
-   return true;
+   return !entry->is_uniform;
 }
 
 /* TODO: Generalize to other bit sizes */

src/asahi/compiler/agx_register_allocate.c

@@ -382,9 +382,12 @@ agx_ra(agx_context *ctx)
             if (agx_is_null(ins->src[i])) continue;
             assert(ins->src[i].size == ins->dest[0].size);
 
+            bool is_uniform = ins->src[i].type == AGX_INDEX_UNIFORM;
+
             copies[n++] = (struct agx_copy) {
                .dest = base + (i * width),
-               .src = agx_index_to_reg(ssa_to_reg, ins->src[i]) ,
+               .is_uniform = is_uniform,
+               .src = is_uniform ? ins->src[i].value : agx_index_to_reg(ssa_to_reg, ins->src[i]),
                .size = ins->src[i].size
             };
          }