i965/fs_nir: Handle sample ID, position, and mask better

Before, we were emitting the full pile of setup instructions for sample_id
and sample_pos every time they were used.  With this commit, we emit them
in their own pass once at the beginning of the shader and simply emit uses
later on.  When it comes time for setting up VS, we can put setup for its
special values in the same pass.

2 files changed, 71 insertions, 12 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index 8f6b3b0557..0cd3966ff5 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -574,6 +574,7 @@ public:
    void nir_setup_uniforms(nir_shader *shader);
    void nir_setup_uniform(nir_variable *var);
    void nir_setup_builtin_uniform(nir_variable *var);
+   void nir_emit_system_values(nir_shader *shader);
    void nir_emit_impl(nir_function_impl *impl);
    void nir_emit_cf_list(exec_list *list);
    void nir_emit_if(nir_if *if_stmt);
@@ -701,6 +702,7 @@ public:
    fs_reg nir_inputs;
    fs_reg nir_outputs;
    fs_reg nir_uniforms;
+   fs_reg *nir_system_values;
 
    /** @{ debug annotation info */
    const char *current_annotation;
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index 9046e262e7..32f9538fc8 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -106,6 +106,8 @@ fs_visitor::emit_nir_code()
       nir_setup_uniforms(nir);
    }
 
+   nir_emit_system_values(nir);
+
    nir_globals = ralloc_array(mem_ctx, fs_reg, nir->reg_alloc);
    foreach_list_typed(nir_register, reg, node, &nir->registers) {
       unsigned array_elems =
@@ -289,6 +291,60 @@ fs_visitor::nir_setup_builtin_uniform(nir_variable *var)
    }
 }
 
+static bool
+emit_system_values_block(nir_block *block, void *void_visitor)
+{
+   fs_visitor *v = (fs_visitor *)void_visitor;
+   fs_reg *reg;
+
+   nir_foreach_instr(block, instr) {
+      if (instr->type != nir_instr_type_intrinsic)
+         continue;
+
+      nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+      switch (intrin->intrinsic) {
+      case nir_intrinsic_load_sample_pos:
+         assert(v->stage == MESA_SHADER_FRAGMENT);
+         reg = &v->nir_system_values[SYSTEM_VALUE_SAMPLE_POS];
+         if (reg->file == BAD_FILE)
+            *reg = *v->emit_samplepos_setup();
+         break;
+
+      case nir_intrinsic_load_sample_id:
+         assert(v->stage == MESA_SHADER_FRAGMENT);
+         reg = &v->nir_system_values[SYSTEM_VALUE_SAMPLE_ID];
+         if (reg->file == BAD_FILE)
+            *reg = *v->emit_sampleid_setup();
+         break;
+
+      case nir_intrinsic_load_sample_mask_in:
+         assert(v->stage == MESA_SHADER_FRAGMENT);
+         assert(v->brw->gen >= 7);
+         reg = &v->nir_system_values[SYSTEM_VALUE_SAMPLE_MASK_IN];
+         if (reg->file == BAD_FILE)
+            *reg = fs_reg(retype(brw_vec8_grf(v->payload.sample_mask_in_reg, 0),
+                                 BRW_REGISTER_TYPE_D));
+         break;
+
+      default:
+         break;
+      }
+   }
+
+   return true;
+}
+
+void
+fs_visitor::nir_emit_system_values(nir_shader *shader)
+{
+   nir_system_values = ralloc_array(mem_ctx, fs_reg, SYSTEM_VALUE_MAX);
+   nir_foreach_overload(shader, overload) {
+      assert(strcmp(overload->function->name, "main") == 0);
+      assert(overload->impl);
+      nir_foreach_block(overload->impl, emit_system_values_block, this);
+   }
+}
+
 void
 fs_visitor::nir_emit_impl(nir_function_impl *impl)
 {
@@ -1276,26 +1332,27 @@ fs_visitor::nir_emit_intrinsic(nir_intrinsic_instr *instr)
       assert(!"TODO");
 
    case nir_intrinsic_load_sample_mask_in: {
-      assert(brw->gen >= 7);
-      fs_reg reg = fs_reg(retype(brw_vec8_grf(payload.sample_mask_in_reg, 0),
-                          BRW_REGISTER_TYPE_D));
-      dest.type = reg.type;
-      emit(MOV(dest, reg));
+      fs_reg sample_mask_in = nir_system_values[SYSTEM_VALUE_SAMPLE_MASK_IN];
+      assert(sample_mask_in.file != BAD_FILE);
+      dest.type = sample_mask_in.type;
+      emit(MOV(dest, sample_mask_in));
       break;
    }
 
    case nir_intrinsic_load_sample_pos: {
-      fs_reg *reg = emit_samplepos_setup();
-      dest.type = reg->type;
-      emit(MOV(dest, *reg));
-      emit(MOV(offset(dest, 1), offset(*reg, 1)));
+      fs_reg sample_pos = nir_system_values[SYSTEM_VALUE_SAMPLE_POS];
+      assert(sample_pos.file != BAD_FILE);
+      dest.type = sample_pos.type;
+      emit(MOV(dest, sample_pos));
+      emit(MOV(offset(dest, 1), offset(sample_pos, 1)));
       break;
    }
 
    case nir_intrinsic_load_sample_id: {
-      fs_reg *reg = emit_sampleid_setup();
-      dest.type = reg->type;
-      emit(MOV(dest, *reg));
+      fs_reg sample_id = nir_system_values[SYSTEM_VALUE_SAMPLE_ID];
+      assert(sample_id.file != BAD_FILE);
+      dest.type = sample_id.type;
+      emit(MOV(dest, sample_id));
       break;
    }