[Mesa-dev] [PATCH v7 1/2] spirv: add/hookup SpvCapabilityStencilExportEXT

[Caio Marcelo de Oliveira Filho]

From: Gustavo Lima Chaves <gustavo.lima.chaves at intel.com>

v2:
An attempt to support SpvExecutionModeStencilRefReplacingEXT's behavior
also follows, with the interpretation to said mode being we prevent
writes to the built-in FragStencilRefEXT variable when the execution
mode isn't set.

v3:
A more cautious reading of 1db44252d01bf7539452ccc2b5210c74b8dcd573 led
me to a missing change that would stop (what I later discovered were)
GPU hangs on the CTS test written to exercise this.

v4:
Turn FragStencilRefEXT decoration usage without StencilRefReplacingEXT
mode into a warning, instead of trying to make the variable read-only.
If we are to follow the originating extension on GL, the built-in
variable in question should never be readable anyway.

v5/v6: rebases.

v7:
Fix check for gen9 lost in rebase. (Ilia)
Reduce the scope of the bool used to track whether
SpvExecutionModeStencilRefReplacingEXT was used. Was in shader_info,
moved to vtn_builder. (Jason)
---

Moved the history and some of the code from the other patch. Keeping
the patch in Gustavo name since the only real change I made was
trivial (moving a boolean between structs).

 src/compiler/shader_info.h         |  1 +
 src/compiler/spirv/spirv_to_nir.c  |  8 ++++++++
 src/compiler/spirv/vtn_private.h   |  1 +
 src/compiler/spirv/vtn_variables.c | 10 ++++++++++
 4 files changed, 20 insertions(+)

diff --git a/src/compiler/shader_info.h b/src/compiler/shader_info.h
index afc53a88405..81f844d36ae 100644
--- a/src/compiler/shader_info.h
+++ b/src/compiler/shader_info.h
@@ -56,6 +56,7 @@ struct spirv_supported_capabilities {
    bool trinary_minmax;
    bool descriptor_array_dynamic_indexing;
    bool runtime_descriptor_array;
+   bool stencil_export;
 };
 
 typedef struct shader_info {
diff --git a/src/compiler/spirv/spirv_to_nir.c b/src/compiler/spirv/spirv_to_nir.c
index 78437428aa7..bc8e77c35c3 100644
--- a/src/compiler/spirv/spirv_to_nir.c
+++ b/src/compiler/spirv/spirv_to_nir.c
@@ -3396,6 +3396,10 @@ vtn_handle_preamble_instruction(struct vtn_builder *b, SpvOp opcode,
          spv_check_supported(runtime_descriptor_array, cap);
          break;
 
+      case SpvCapabilityStencilExportEXT:
+         spv_check_supported(stencil_export, cap);
+         break;
+
       default:
          vtn_fail("Unhandled capability");
       }
@@ -3573,6 +3577,10 @@ vtn_handle_execution_mode(struct vtn_builder *b, struct vtn_value *entry_point,
    case SpvExecutionModeContractionOff:
       break; /* OpenCL */
 
+   case SpvExecutionModeStencilRefReplacingEXT:
+      b->outputs_stencil_ref = true;
+      break;
+
    default:
       vtn_fail("Unhandled execution mode");
    }
diff --git a/src/compiler/spirv/vtn_private.h b/src/compiler/spirv/vtn_private.h
index b501bbf9b4a..75f78363b46 100644
--- a/src/compiler/spirv/vtn_private.h
+++ b/src/compiler/spirv/vtn_private.h
@@ -574,6 +574,7 @@ struct vtn_builder {
    struct vtn_value *entry_point;
    bool origin_upper_left;
    bool pixel_center_integer;
+   bool outputs_stencil_ref;
 
    struct vtn_function *func;
    struct exec_list functions;
diff --git a/src/compiler/spirv/vtn_variables.c b/src/compiler/spirv/vtn_variables.c
index fd8ab7f247a..2bc8b5e9003 100644
--- a/src/compiler/spirv/vtn_variables.c
+++ b/src/compiler/spirv/vtn_variables.c
@@ -1354,6 +1354,10 @@ vtn_get_builtin_location(struct vtn_builder *b,
       *location = SYSTEM_VALUE_SUBGROUP_LT_MASK,
       set_mode_system_value(b, mode);
       break;
+   case SpvBuiltInFragStencilRefEXT:
+      *location = FRAG_RESULT_STENCIL;
+      vtn_assert(*mode == nir_var_shader_out);
+      break;
    default:
       vtn_fail("unsupported builtin");
    }
@@ -1425,6 +1429,12 @@ apply_var_decoration(struct vtn_builder *b, nir_variable *nir_var,
       case SpvBuiltInSamplePosition:
          nir_var->data.origin_upper_left = b->origin_upper_left;
          break;
+      case SpvBuiltInFragStencilRefEXT:
+         if (!b->outputs_stencil_ref) {
+            vtn_warn("The StencilRefReplacingEXT mode should be declared when"
+                     " the decoration FragStencilRefEXT is used on a variable");
+         }
+         break;
       default:
          break;
       }
-- 
2.17.0