[Mesa-dev] [PATCH v2 5/9] nir: Add a concept of constant data associated with a shader

[Jason Ekstrand]

This commit adds a concept to NIR of having a blob of constant data
associated with a shader.  Instead of being a UBO or uniform that can be
manipulated by the client, this constant data considered part of the
shader and remains constant across all invocations of the given shader
until the end of time.  To access this constant data from the shader, we
add a new load_constant intrinsic.  The intention is that drivers will
eventually lower load_constant intrinsics to load_ubo, load_uniform, or
something similar.  Constant data will be used by the optimization pass
in the next commit but this concept may also be useful for OpenCL.

v2 (Jason Ekstrand):
 - Rename num_constants to constant_data_size (anholt)
---
 src/compiler/nir/nir.h             |  8 ++++++++
 src/compiler/nir/nir_clone.c       |  6 ++++++
 src/compiler/nir/nir_intrinsics.py |  2 ++
 src/compiler/nir/nir_serialize.c   | 12 ++++++++++++
 src/compiler/nir/nir_sweep.c       |  2 ++
 5 files changed, 30 insertions(+)

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index e35bef612df..cc5f88d6f54 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2067,6 +2067,14 @@ typedef struct nir_shader {
     * access plus one
     */
    unsigned num_inputs, num_uniforms, num_outputs, num_shared;
+
+   /** Constant data associated with this shader.
+    *
+    * Constant data is loaded through load_constant intrinsics.  See also
+    * nir_opt_large_constants.
+    */
+   void *constant_data;
+   unsigned constant_data_size;
 } nir_shader;
 
 static inline nir_function_impl *
diff --git a/src/compiler/nir/nir_clone.c b/src/compiler/nir/nir_clone.c
index 23bb17eeba3..989c5051a54 100644
--- a/src/compiler/nir/nir_clone.c
+++ b/src/compiler/nir/nir_clone.c
@@ -734,6 +734,12 @@ nir_shader_clone(void *mem_ctx, const nir_shader *s)
    ns->num_outputs = s->num_outputs;
    ns->num_shared = s->num_shared;
 
+   ns->constant_data_size = s->constant_data_size;
+   if (s->constant_data_size > 0) {
+      ns->constant_data = ralloc_size(ns, s->constant_data_size);
+      memcpy(ns->constant_data, s->constant_data, s->constant_data_size);
+   }
+
    free_clone_state(&state);
 
    return ns;
diff --git a/src/compiler/nir/nir_intrinsics.py b/src/compiler/nir/nir_intrinsics.py
index d9d0bbdfccf..44a5b76beb6 100644
--- a/src/compiler/nir/nir_intrinsics.py
+++ b/src/compiler/nir/nir_intrinsics.py
@@ -532,6 +532,8 @@ load("per_vertex_output", 2, [BASE, COMPONENT], [CAN_ELIMINATE])
 load("shared", 1, [BASE], [CAN_ELIMINATE])
 # src[] = { offset }. const_index[] = { base, range }
 load("push_constant", 1, [BASE, RANGE], [CAN_ELIMINATE, CAN_REORDER])
+# src[] = { offset }. const_index[] = { base, range }
+load("constant", 1, [BASE, RANGE], [CAN_ELIMINATE, CAN_REORDER])
 
 # Stores work the same way as loads, except now the first source is the value
 # to store and the second (and possibly third) source specify where to store
diff --git a/src/compiler/nir/nir_serialize.c b/src/compiler/nir/nir_serialize.c
index cc4bf23aa0f..6a30738c2d7 100644
--- a/src/compiler/nir/nir_serialize.c
+++ b/src/compiler/nir/nir_serialize.c
@@ -1116,6 +1116,10 @@ nir_serialize(struct blob *blob, const nir_shader *nir)
       write_function_impl(&ctx, fxn->impl);
    }
 
+   blob_write_uint32(blob, nir->constant_data_size);
+   if (nir->constant_data_size > 0)
+      blob_write_bytes(blob, nir->constant_data, nir->constant_data_size);
+
    *(uintptr_t *)(blob->data + idx_size_offset) = ctx.next_idx;
 
    _mesa_hash_table_destroy(ctx.remap_table, NULL);
@@ -1169,6 +1173,14 @@ nir_deserialize(void *mem_ctx,
    nir_foreach_function(fxn, ctx.nir)
       fxn->impl = read_function_impl(&ctx, fxn);
 
+   ctx.nir->constant_data_size = blob_read_uint32(blob);
+   if (ctx.nir->constant_data_size > 0) {
+      ctx.nir->constant_data =
+         ralloc_size(ctx.nir, ctx.nir->constant_data_size);
+      blob_copy_bytes(blob, ctx.nir->constant_data,
+                      ctx.nir->constant_data_size);
+   }
+
    free(ctx.idx_table);
 
    return ctx.nir;
diff --git a/src/compiler/nir/nir_sweep.c b/src/compiler/nir/nir_sweep.c
index b14bf139c1b..aab641388db 100644
--- a/src/compiler/nir/nir_sweep.c
+++ b/src/compiler/nir/nir_sweep.c
@@ -167,6 +167,8 @@ nir_sweep(nir_shader *nir)
       sweep_function(nir, func);
    }
 
+   ralloc_steal(nir, nir->constant_data);
+
    /* Free everything we didn't steal back. */
    ralloc_free(rubbish);
 }
-- 
2.17.1