[Mesa-dev] [RFC] i965: alternative to memctx for cleaning up nir variants

[Rob Clark]

From: Rob Clark <robclark at freedesktop.org>

Jason,

How much do you hate this idea?  Seems like an easy alternative to
using ralloc ctx's to clean up nir variants/clones, which would let
us drop the parent memctx for nir_shader_create()/clone(), making
it easier to introduce reference counting.

---
 src/mesa/drivers/dri/i965/brw_compiler.h          | 22 ++++++++++++++++++++++
 src/mesa/drivers/dri/i965/brw_fs.cpp              |  6 ++++--
 src/mesa/drivers/dri/i965/brw_vec4.cpp            |  3 ++-
 src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp |  3 ++-
 4 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_compiler.h b/src/mesa/drivers/dri/i965/brw_compiler.h
index c9e0317..eb1087a 100644
--- a/src/mesa/drivers/dri/i965/brw_compiler.h
+++ b/src/mesa/drivers/dri/i965/brw_compiler.h
@@ -26,6 +26,7 @@
 #include <stdio.h>
 #include "brw_device_info.h"
 #include "main/mtypes.h"
+#include "nir.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -651,6 +652,27 @@ struct brw_gs_prog_data
 
 /** @} */
 
+#ifdef __cplusplus
+/* A common pattern is for brw_compile_xyz to create a clone of the original
+ * shader, modify it (various lowering passes, etc), and then throw it away.
+ * The scoped_clone helper class is just a way to use RAII to clean up the
+ * shader when it goes out of scope.
+ */
+class scoped_clone
+{
+public:
+   nir_shader *shader;
+   scoped_clone(const nir_shader *s)
+   {
+      shader = nir_shader_clone(NULL, s);
+   }
+   ~scoped_clone()
+   {
+      ralloc_free(shader);
+   }
+};
+#endif
+
 /**
  * Compile a vertex shader.
  *
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index c833ef0..44ea156 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -5490,7 +5490,8 @@ brw_compile_fs(const struct brw_compiler *compiler, void *log_data,
                unsigned *final_assembly_size,
                char **error_str)
 {
-   nir_shader *shader = nir_shader_clone(mem_ctx, src_shader);
+   scoped_clone sc(src_shader);
+   nir_shader *shader = sc.shader;
    shader = brw_nir_apply_sampler_key(shader, compiler->devinfo, &key->tex,
                                       true);
    shader = brw_postprocess_nir(shader, compiler->devinfo, true);
@@ -5616,7 +5617,8 @@ brw_compile_cs(const struct brw_compiler *compiler, void *log_data,
                unsigned *final_assembly_size,
                char **error_str)
 {
-   nir_shader *shader = nir_shader_clone(mem_ctx, src_shader);
+   scoped_clone sc(src_shader);
+   nir_shader *shader = sc.shader;
    shader = brw_nir_apply_sampler_key(shader, compiler->devinfo, &key->tex,
                                       true);
    shader = brw_postprocess_nir(shader, compiler->devinfo, true);
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index a697bdf..a89e884 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1957,7 +1957,8 @@ brw_compile_vs(const struct brw_compiler *compiler, void *log_data,
                unsigned *final_assembly_size,
                char **error_str)
 {
-   nir_shader *shader = nir_shader_clone(mem_ctx, src_shader);
+   scoped_clone sc(src_shader);
+   nir_shader *shader = sc.shader;
    shader = brw_nir_apply_sampler_key(shader, compiler->devinfo, &key->tex,
                                       compiler->scalar_stage[MESA_SHADER_VERTEX]);
    shader = brw_postprocess_nir(shader, compiler->devinfo,
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
index b13d36e..9ed7e0d 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
@@ -617,7 +617,8 @@ brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
    memset(&c, 0, sizeof(c));
    c.key = *key;
 
-   nir_shader *shader = nir_shader_clone(mem_ctx, src_shader);
+   scoped_clone sc(src_shader);
+   nir_shader *shader = sc.shader;
    shader = brw_nir_apply_sampler_key(shader, compiler->devinfo, &key->tex,
                                       compiler->scalar_stage[MESA_SHADER_GEOMETRY]);
    shader = brw_postprocess_nir(shader, compiler->devinfo,
-- 
2.5.0