[Mesa-dev] [PATCH] nir: special hack for TGSI vs indirect inputs

[Rob Clark]

From: Rob Clark <robclark at freedesktop.org>

TGSI doesn't know about array input (or output[*]) variables.  If the
INPUT file is addressed indirectly, we must treat the entire INPUT
"register file" as one contiguous array.  However tgsi_to_nir cannot
declare all the inputs as a single array var, as this would loose
varying slot and interpolation info.

This hack provides the extra information that the compiler backend
needs so that all the N inputs can be organized as a single array for
direct and indirect access.

[*] tgsi_to_nir does not generate indirect output stores, otherwise we
would need a similar hack for outputs

Signed-off-by: Rob Clark <robclark at freedesktop.org>
---
Yes, sorry, I know, TGSI is horrible.  But I don't really have any
better ideas about how to handle this.

 src/gallium/auxiliary/nir/tgsi_to_nir.c |  3 +++
 src/glsl/nir/nir.h                      | 14 ++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/gallium/auxiliary/nir/tgsi_to_nir.c b/src/gallium/auxiliary/nir/tgsi_to_nir.c
index 94d992b..4a57f9e 100644
--- a/src/gallium/auxiliary/nir/tgsi_to_nir.c
+++ b/src/gallium/auxiliary/nir/tgsi_to_nir.c
@@ -1973,6 +1973,9 @@ tgsi_to_nir(const void *tgsi_tokens,
                                   options);
    s = c->build.shader;
 
+   if (c->scan->indirect_files & (1 << TGSI_FILE_INPUT))
+      s->info.tgsi_hack_indirect_inputs = true;
+
    s->num_inputs = scan.file_max[TGSI_FILE_INPUT] + 1;
    s->num_uniforms = scan.const_file_max[0] + 1;
    s->num_outputs = scan.file_max[TGSI_FILE_OUTPUT] + 1;
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index bedcc0d..629c32f 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1510,6 +1510,20 @@ typedef struct nir_shader_info {
    /** Was this shader linked with any transform feedback varyings? */
    bool has_transform_feedback_varyings;
 
+   /**
+    * Special hack for tgsi_to_nir.  Due to limitations in TGSI, when
+    * there is indirect addressing of the input file, we don't actually
+    * know which inputs are part of an array and which are not.  We
+    * cannot convert all the inputs to a single array (which maps to
+    * TGSI's IN[ADDR[0].x+n] semantics), since we need the varying-slot
+    * and interpolation information still.
+    *
+    * NOTE that tgsi_to_nir doesn't generate indirect output_store's,
+    * otherwise we would need a similar flag to indicate indirect
+    * output file addressing.
+    */
+   bool tgsi_hack_indirect_inputs;
+
    union {
       struct {
          /** The number of vertices recieves per input primitive */
-- 
2.5.0