[Mesa-dev] [PATCH 2/2] nir: add lowering for gl_HelperInvocation

[Rob Clark]

Signed-off-by: Rob Clark <robdclark at gmail.com>
---
I can't say for sure that this will work on all drivers, but it is
what the blob driver does, and it seems to make deqp happy.  I could
move this to it's own pass inside ir3, but that seemed like overkill

 src/compiler/nir/nir.h                      | 10 ++++++++++
 src/compiler/nir/nir_lower_system_values.c  | 17 +++++++++++++++++
 src/gallium/drivers/freedreno/ir3/ir3_nir.c |  1 +
 3 files changed, 28 insertions(+)

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 073ab4e82ea..de3d55d83af 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1963,6 +1963,16 @@ typedef struct nir_shader_compiler_options {
     */
    bool lower_base_vertex;
 
+   /**
+    * If enabled, gl_HelperInvocation will be lowered as:
+    *
+    *   !((1 << gl_SampleID) & gl_SampleMaskIN[0]))
+    *
+    * TODO any hw w/ more than 32 samples?  For them (if they
+    * used this option), a bit more math would be involved.
+    */
+   bool lower_helper_invocation;
+
    bool lower_cs_local_index_from_id;
 
    bool lower_device_index_to_zero;
diff --git a/src/compiler/nir/nir_lower_system_values.c b/src/compiler/nir/nir_lower_system_values.c
index 487da042620..6668cbb5dcd 100644
--- a/src/compiler/nir/nir_lower_system_values.c
+++ b/src/compiler/nir/nir_lower_system_values.c
@@ -136,6 +136,23 @@ convert_block(nir_block *block, nir_builder *b)
                               nir_load_first_vertex(b));
          break;
 
+      case SYSTEM_VALUE_HELPER_INVOCATION:
+         if (b->shader->options->lower_helper_invocation) {
+            nir_ssa_def *tmp;
+
+            tmp = nir_ushr(b,
+                           nir_imm_int(b, 1),
+                           nir_load_sample_id(b));
+
+            tmp = nir_iand(b,
+                           nir_load_sample_mask_in(b),
+                           tmp);
+
+            sysval = nir_inot(b, nir_i2b(b, tmp));
+         }
+
+         break;
+
       case SYSTEM_VALUE_INSTANCE_INDEX:
          sysval = nir_iadd(b,
                            nir_load_instance_id(b),
diff --git a/src/gallium/drivers/freedreno/ir3/ir3_nir.c b/src/gallium/drivers/freedreno/ir3/ir3_nir.c
index cd1f9c526f2..341d990b269 100644
--- a/src/gallium/drivers/freedreno/ir3/ir3_nir.c
+++ b/src/gallium/drivers/freedreno/ir3/ir3_nir.c
@@ -51,6 +51,7 @@ static const nir_shader_compiler_options options = {
 		.lower_extract_byte = true,
 		.lower_extract_word = true,
 		.lower_all_io_to_temps = true,
+		.lower_helper_invocation = true,
 };
 
 struct nir_shader *
-- 
2.17.0