intel,nir: Move gl_LocalInvocationID lowering to nir_lower_system_values

It's not at all intel-specific; the formula is dictated by OpenGL and
Vulkan.  The only intel-specific thing is that we need the lowering.  As
a nice side-effect, the new version is variable-group-size ready.

Reviewed-by: Plamena Manolova <[email protected]>

2 files changed, 49 insertions, 1 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index b0cff50eaf2..1dd605010f6 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2178,6 +2178,7 @@ typedef struct nir_shader_compiler_options {
    bool lower_helper_invocation;
 
    bool lower_cs_local_index_from_id;
+   bool lower_cs_local_id_from_index;
 
    bool lower_device_index_to_zero;
 
diff --git a/src/compiler/nir/nir_lower_system_values.c b/src/compiler/nir/nir_lower_system_values.c
index fbc40573579..08a9e8be44a 100644
--- a/src/compiler/nir/nir_lower_system_values.c
+++ b/src/compiler/nir/nir_lower_system_values.c
@@ -51,6 +51,45 @@ build_local_group_size(nir_builder *b)
    return local_size;
 }
 
+static nir_ssa_def *
+build_local_invocation_id(nir_builder *b)
+{
+   if (b->shader->options->lower_cs_local_id_from_index) {
+      /* We lower gl_LocalInvocationID from gl_LocalInvocationIndex based
+       * on this formula:
+       *
+       *    gl_LocalInvocationID.x =
+       *       gl_LocalInvocationIndex % gl_WorkGroupSize.x;
+       *    gl_LocalInvocationID.y =
+       *       (gl_LocalInvocationIndex / gl_WorkGroupSize.x) %
+       *       gl_WorkGroupSize.y;
+       *    gl_LocalInvocationID.z =
+       *       (gl_LocalInvocationIndex /
+       *        (gl_WorkGroupSize.x * gl_WorkGroupSize.y)) %
+       *       gl_WorkGroupSize.z;
+       *
+       * However, the final % gl_WorkGroupSize.z does nothing unless we
+       * accidentally end up with a gl_LocalInvocationIndex that is too
+       * large so it can safely be omitted.
+       */
+      nir_ssa_def *local_index = nir_load_local_invocation_index(b);
+      nir_ssa_def *local_size = build_local_group_size(b);
+
+      nir_ssa_def *id_x, *id_y, *id_z;
+      id_x = nir_umod(b, local_index,
+                         nir_channel(b, local_size, 0));
+      id_y = nir_umod(b, nir_udiv(b, local_index,
+                                     nir_channel(b, local_size, 0)),
+                         nir_channel(b, local_size, 1));
+      id_z = nir_udiv(b, local_index,
+                         nir_imul(b, nir_channel(b, local_size, 0),
+                                     nir_channel(b, local_size, 1)));
+      return nir_vec3(b, id_x, id_y, id_z);
+   } else {
+      return nir_load_local_invocation_id(b);
+   }
+}
+
 static bool
 convert_block(nir_block *block, nir_builder *b)
 {
@@ -91,7 +130,7 @@ convert_block(nir_block *block, nir_builder *b)
           */
          nir_ssa_def *group_size = build_local_group_size(b);
          nir_ssa_def *group_id = nir_load_work_group_id(b);
-         nir_ssa_def *local_id = nir_load_local_invocation_id(b);
+         nir_ssa_def *local_id = build_local_invocation_id(b);
 
          sysval = nir_iadd(b, nir_imul(b, group_id, group_size), local_id);
          break;
@@ -126,6 +165,14 @@ convert_block(nir_block *block, nir_builder *b)
          break;
       }
 
+      case SYSTEM_VALUE_LOCAL_INVOCATION_ID:
+         /* If lower_cs_local_id_from_index is true, then we derive the local
+          * index from the local id.
+          */
+         if (b->shader->options->lower_cs_local_id_from_index)
+            sysval = build_local_invocation_id(b);
+         break;
+
       case SYSTEM_VALUE_LOCAL_GROUP_SIZE: {
          sysval = build_local_group_size(b);
          break;