Hi Eric,

I'm working on lima gp compiler which should benefit from nir lowering
uniform load to scalar.
I notice you write the nir_lower_io_to_scalar.c which support lowering
shader_in/shader_out
but left the uniform lowering in vc4 driver, any reason why not
implement in the nir_lower_io_to_scalar.c?

I'm new to nir, tried to add it but seems not correct after
optimization pass. So I should missing
some place, anyone can help to point out?

Thanks,
Qiang
diff --git a/src/compiler/nir/nir_intrinsics.h b/src/compiler/nir/nir_intrinsics.h
index 3a519a73..93bf0fc 100644
--- a/src/compiler/nir/nir_intrinsics.h
+++ b/src/compiler/nir/nir_intrinsics.h
@@ -392,8 +392,8 @@ BARYCENTRIC(at_offset, 1, 2)
 #define LOAD(name, srcs, num_indices, idx0, idx1, idx2, flags) \
    INTRINSIC(load_##name, srcs, ARR(1, 1, 1, 1), true, 0, 0, num_indices, idx0, idx1, idx2, flags)
 
-/* src[] = { offset }. const_index[] = { base, range } */
-LOAD(uniform, 1, 2, BASE, RANGE, xx, NIR_INTRINSIC_CAN_ELIMINATE | NIR_INTRINSIC_CAN_REORDER)
+/* src[] = { offset }. const_index[] = { base, range, component } */
+LOAD(uniform, 1, 2, BASE, RANGE, COMPONENT, NIR_INTRINSIC_CAN_ELIMINATE | NIR_INTRINSIC_CAN_REORDER)
 /* src[] = { buffer_index, offset }. No const_index */
 LOAD(ubo, 2, 0, xx, xx, xx, NIR_INTRINSIC_CAN_ELIMINATE | NIR_INTRINSIC_CAN_REORDER)
 /* src[] = { offset }. const_index[] = { base, component } */
diff --git a/src/compiler/nir/nir_lower_io.c b/src/compiler/nir/nir_lower_io.c
index 1ae2cc7..566f8d0 100644
--- a/src/compiler/nir/nir_lower_io.c
+++ b/src/compiler/nir/nir_lower_io.c
@@ -208,7 +208,7 @@ lower_load(nir_intrinsic_instr *intrin, struct lower_io_state *state,
    load->num_components = intrin->num_components;
 
    nir_intrinsic_set_base(load, var->data.driver_location);
-   if (mode == nir_var_shader_in || mode == nir_var_shader_out)
+   if (mode == nir_var_shader_in || mode == nir_var_shader_out || mode == nir_var_uniform)
       nir_intrinsic_set_component(load, component);
 
    if (load->intrinsic == nir_intrinsic_load_uniform)
diff --git a/src/compiler/nir/nir_lower_io_to_scalar.c b/src/compiler/nir/nir_lower_io_to_scalar.c
index f2345d5..d838770 100644
--- a/src/compiler/nir/nir_lower_io_to_scalar.c
+++ b/src/compiler/nir/nir_lower_io_to_scalar.c
@@ -26,8 +26,8 @@
 
 /** @file nir_lower_io_to_scalar.c
  *
- * Replaces nir_load_input/nir_store_output operations with num_components !=
- * 1 with individual per-channel operations.
+ * Replaces nir_load_input/nir_store_output/nir_load_uniform operations
+ * with num_components != 1 with individual per-channel operations.
  */
 
 static void
@@ -63,6 +63,39 @@ lower_load_input_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
 }
 
 static void
+lower_load_uniform_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
+{
+   b->cursor = nir_before_instr(&intr->instr);
+
+   assert(intr->dest.is_ssa);
+
+   nir_ssa_def *loads[4];
+
+   for (unsigned i = 0; i < intr->num_components; i++) {
+      nir_intrinsic_instr *chan_intr =
+         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
+      nir_ssa_dest_init(&chan_intr->instr, &chan_intr->dest,
+                        1, intr->dest.ssa.bit_size, NULL);
+      chan_intr->num_components = 1;
+
+      nir_intrinsic_set_base(chan_intr, nir_intrinsic_base(intr));
+      nir_intrinsic_set_component(chan_intr, nir_intrinsic_component(intr) + i);
+      nir_intrinsic_set_range(chan_intr, nir_intrinsic_range(intr));
+      /* offset */
+      nir_src_copy(&chan_intr->src[0], &intr->src[0], chan_intr);
+
+      nir_builder_instr_insert(b, &chan_intr->instr);
+
+      loads[i] = &chan_intr->dest.ssa;
+   }
+
+   nir_ssa_def_rewrite_uses(&intr->dest.ssa,
+                            nir_src_for_ssa(nir_vec(b, loads,
+                                                    intr->num_components)));
+   nir_instr_remove(&intr->instr);
+}
+
+static void
 lower_store_output_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
 {
    b->cursor = nir_before_instr(&intr->instr);
@@ -119,6 +152,10 @@ nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask)
                   if (mask & nir_var_shader_out)
                      lower_store_output_to_scalar(&b, intr);
                   break;
+               case nir_intrinsic_load_uniform:
+                  if (mask & nir_var_uniform)
+                     lower_load_uniform_to_scalar(&b, intr);
+                  break;
                default:
                   break;
                }
diff --git a/src/gallium/drivers/lima/ir/gp/nir.c b/src/gallium/drivers/lima/ir/gp/nir.c
index 1f6b91d..e71c0a0 100644
--- a/src/gallium/drivers/lima/ir/gp/nir.c
+++ b/src/gallium/drivers/lima/ir/gp/nir.c
@@ -123,8 +123,8 @@ static gpir_node *gpir_emit_intrinsic(gpir_compiler *comp, nir_intrinsic_instr *
       if (!lnode)
          return NULL;
 
-      lnode->index = instr->const_index[info->index_map[NIR_INTRINSIC_BASE] - 1];
-      lnode->component = instr->const_index[info->index_map[NIR_INTRINSIC_COMPONENT] - 1];
+      lnode->index = nir_intrinsic_base(instr);
+      lnode->component = nir_intrinsic_component(instr);
 
       return &lnode->node;
 
@@ -133,8 +133,8 @@ static gpir_node *gpir_emit_intrinsic(gpir_compiler *comp, nir_intrinsic_instr *
       if (!snode)
          return NULL;
 
-      snode->index = instr->const_index[info->index_map[NIR_INTRINSIC_BASE] - 1];
-      snode->component = instr->const_index[info->index_map[NIR_INTRINSIC_COMPONENT] - 1];
+      snode->index = nir_intrinsic_base(instr);
+      snode->component = nir_intrinsic_component(instr);
 
       child = gpir_node_find(comp, instr->src);
       snode->child = child;
diff --git a/src/gallium/drivers/lima/lima_program.c b/src/gallium/drivers/lima/lima_program.c
index 68cfeb5..8ba6511 100644
--- a/src/gallium/drivers/lima/lima_program.c
+++ b/src/gallium/drivers/lima/lima_program.c
@@ -63,7 +63,8 @@ lima_program_optimize_nir(struct nir_shader *s)
    bool progress;
 
    NIR_PASS_V(s, nir_lower_load_const_to_scalar);
-   NIR_PASS_V(s, nir_lower_io_to_scalar, nir_var_shader_in|nir_var_shader_out);
+   NIR_PASS_V(s, nir_lower_io_to_scalar,
+              nir_var_shader_in|nir_var_shader_out|nir_var_uniform);
 
    do {
       progress = false;
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