[Mesa-dev] [PATCH v2 2/2] mesa/st: only do scalar lowerings if driver benefits

[Christian Gmeiner]

As not every (upcoming) backend compiler is happy with
nir_lower_xxx_to_scalar lowerings do them only if the backend
is scalar (and not vec4) based.

Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
---
 src/mesa/state_tracker/st_glsl_to_nir.cpp | 39 +++++++++++++++++------
 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index c8c2ef6cff..67622c127a 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -315,15 +315,18 @@ st_nir_assign_uniform_locations(struct gl_context *ctx,
 }
 
 void
-st_nir_opts(nir_shader *nir)
+st_nir_opts(nir_shader *nir, bool scalar)
 {
    bool progress;
    do {
       progress = false;
 
       NIR_PASS_V(nir, nir_lower_vars_to_ssa);
-      NIR_PASS_V(nir, nir_lower_alu_to_scalar);
-      NIR_PASS_V(nir, nir_lower_phis_to_scalar);
+
+      if (scalar) {
+         NIR_PASS_V(nir, nir_lower_alu_to_scalar);
+         NIR_PASS_V(nir, nir_lower_phis_to_scalar);
+      }
 
       NIR_PASS_V(nir, nir_lower_alu);
       NIR_PASS_V(nir, nir_lower_pack);
@@ -362,6 +365,9 @@ st_glsl_to_nir(struct st_context *st, struct gl_program *prog,
 {
    const nir_shader_compiler_options *options =
       st->ctx->Const.ShaderCompilerOptions[prog->info.stage].NirOptions;
+   enum pipe_shader_type type = pipe_shader_type_from_mesa(stage);
+   struct pipe_screen *screen = st->pipe->screen;
+   bool is_scalar = screen->get_shader_param(screen, type, PIPE_SHADER_CAP_SCALAR_ISA);
    assert(options);
 
    if (prog->nir)
@@ -404,7 +410,7 @@ st_glsl_to_nir(struct st_context *st, struct gl_program *prog,
    NIR_PASS_V(nir, nir_split_var_copies);
    NIR_PASS_V(nir, nir_lower_var_copies);
 
-   st_nir_opts(nir);
+   st_nir_opts(nir, is_scalar);
 
    return nir;
 }
@@ -586,7 +592,7 @@ st_nir_get_mesa_program(struct gl_context *ctx,
 }
 
 static void
-st_nir_link_shaders(nir_shader **producer, nir_shader **consumer)
+st_nir_link_shaders(nir_shader **producer, nir_shader **consumer, bool scalar)
 {
    nir_lower_io_arrays_to_elements(*producer, *consumer);
 
@@ -613,8 +619,8 @@ st_nir_link_shaders(nir_shader **producer, nir_shader **consumer)
       NIR_PASS_V(*producer, nir_lower_indirect_derefs, indirect_mask);
       NIR_PASS_V(*consumer, nir_lower_indirect_derefs, indirect_mask);
 
-      st_nir_opts(*producer);
-      st_nir_opts(*consumer);
+      st_nir_opts(*producer, scalar);
+      st_nir_opts(*consumer, scalar);
    }
 }
 
@@ -625,6 +631,20 @@ st_link_nir(struct gl_context *ctx,
             struct gl_shader_program *shader_program)
 {
    struct st_context *st = st_context(ctx);
+   struct pipe_screen *screen = st->pipe->screen;
+   bool is_scalar[MESA_SHADER_STAGES];
+
+   /* Determine scalar property of each shader stage */
+   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
+      struct gl_linked_shader *shader = shader_program->_LinkedShaders[i];
+      enum pipe_shader_type type;
+
+      if (shader == NULL)
+         continue;
+
+      type = pipe_shader_type_from_mesa(shader->Stage);
+      is_scalar[i] = screen->get_shader_param(screen, type, PIPE_SHADER_CAP_SCALAR_ISA);
+   }
 
    /* Determine first and last stage. */
    unsigned first = MESA_SHADER_STAGES;
@@ -653,7 +673,7 @@ st_link_nir(struct gl_context *ctx,
 
       nir_shader *nir = shader->Program->nir;
       NIR_PASS_V(nir, nir_lower_io_to_scalar_early, mask);
-      st_nir_opts(nir);
+      st_nir_opts(nir, is_scalar[i]);
    }
 
    /* Linking the stages in the opposite order (from fragment to vertex)
@@ -668,7 +688,8 @@ st_link_nir(struct gl_context *ctx,
          continue;
 
       st_nir_link_shaders(&shader->Program->nir,
-                          &shader_program->_LinkedShaders[next]->Program->nir);
+                          &shader_program->_LinkedShaders[next]->Program->nir,
+                          is_scalar[i]);
       next = i;
    }
 
-- 
2.17.1