[Mesa-dev] [PATCH v2 2/3] gallium: add support for gl_HelperInvocation semantic

[Ilia Mirkin]

Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/gallium/auxiliary/tgsi/tgsi_strings.c  | 1 +
 src/gallium/docs/source/tgsi.rst           | 8 ++++++++
 src/gallium/include/pipe/p_shader_tokens.h | 3 ++-
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 4 +++-
 4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/gallium/auxiliary/tgsi/tgsi_strings.c b/src/gallium/auxiliary/tgsi/tgsi_strings.c
index 89369d6..fc29a23 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_strings.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_strings.c
@@ -95,6 +95,7 @@ const char *tgsi_semantic_names[TGSI_SEMANTIC_COUNT] =
    "TESSOUTER",
    "TESSINNER",
    "VERTICESIN",
+   "HELPER_INVOCATION",
 };
 
 const char *tgsi_texture_names[TGSI_TEXTURE_COUNT] =
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 01e18f3..e7b0c2f 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -2941,6 +2941,14 @@ TGSI_SEMANTIC_VERTICESIN
 For tessellation evaluation/control shaders, this semantic label indicates the
 number of vertices provided in the input patch. Only the X value is defined.
 
+TGSI_SEMANTIC_HELPER_INVOCATION
+"""""""""""""""""""""""""""""""
+
+For fragment shaders, this semantic indicates whether the current
+invocation is covered or not. Helper invocations are created in order
+to properly compute derivatives, however it may be desirable to skip
+some of the logic in those cases. See ``gl_HelperInvocation`` documentation.
+
 
 Declaration Interpolate
 ^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/gallium/include/pipe/p_shader_tokens.h b/src/gallium/include/pipe/p_shader_tokens.h
index e0ab901..a3137ae 100644
--- a/src/gallium/include/pipe/p_shader_tokens.h
+++ b/src/gallium/include/pipe/p_shader_tokens.h
@@ -185,7 +185,8 @@ struct tgsi_declaration_interp
 #define TGSI_SEMANTIC_TESSOUTER  32 /**< outer tessellation levels */
 #define TGSI_SEMANTIC_TESSINNER  33 /**< inner tessellation levels */
 #define TGSI_SEMANTIC_VERTICESIN 34 /**< number of input vertices */
-#define TGSI_SEMANTIC_COUNT      35 /**< number of semantic values */
+#define TGSI_SEMANTIC_HELPER_INVOCATION 35 /**< current invocation is helper */
+#define TGSI_SEMANTIC_COUNT      36 /**< number of semantic values */
 
 struct tgsi_declaration_semantic
 {
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index b565127..3ad1afd 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -4408,7 +4408,7 @@ const unsigned _mesa_sysval_to_semantic[SYSTEM_VALUE_MAX] = {
    TGSI_SEMANTIC_SAMPLEID,
    TGSI_SEMANTIC_SAMPLEPOS,
    TGSI_SEMANTIC_SAMPLEMASK,
-   0, /* gl_HelperInvocation */
+   TGSI_SEMANTIC_HELPER_INVOCATION,
 
    /* Tessellation shaders
     */
@@ -5139,6 +5139,8 @@ st_translate_program(
           TGSI_SEMANTIC_BASEVERTEX);
    assert(_mesa_sysval_to_semantic[SYSTEM_VALUE_TESS_COORD] ==
           TGSI_SEMANTIC_TESSCOORD);
+   assert(_mesa_sysval_to_semantic[SYSTEM_VALUE_HELPER_INVOCATION] ==
+          TGSI_SEMANTIC_HELPER_INVOCATION);
 
    t = CALLOC_STRUCT(st_translate);
    if (!t) {
-- 
2.4.10