nak: Translate XFB info

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24998>

src/nouveau/compiler/nak.h

@@ -44,6 +44,13 @@ struct nak_fs_key {
 void nak_postprocess_nir(nir_shader *nir, const struct nak_compiler *nak,
                          const struct nak_fs_key *fs_key);
 
+struct nvk_xfb_info {
+   uint32_t stride[4];
+   uint8_t stream[4];
+   uint8_t attr_count[4];
+   uint8_t attr_index[4][128];
+};
+
 struct nak_shader_info {
    gl_shader_stage stage;
 
@@ -77,6 +84,8 @@ struct nak_shader_info {
       uint32_t dummy;
    };
 
+   struct nvk_xfb_info xfb;
+
    /** Shader header for 3D stages */
    uint32_t hdr[32];
 };

src/nouveau/compiler/nak.rs

@@ -315,6 +315,7 @@ pub extern "C" fn nak_compile_shader(
             }
             _ => nak_shader_info__bindgen_ty_1 { dummy: 0 },
         },
+        xfb: unsafe { nak_xfb_from_nir(nir.xfb_info) },
         hdr: nak_sph::encode_header(&s.info, fs_key),
     };
 

src/nouveau/compiler/nak_nir.c

@@ -5,6 +5,7 @@
 
 #include "nak_private.h"
 #include "nir_builder.h"
+#include "nir_xfb_info.h"
 
 #include "util/u_math.h"
 
@@ -317,6 +318,40 @@ nak_nir_lower_varyings(nir_shader *nir, nir_variable_mode modes)
    return progress;
 }
 
+struct nvk_xfb_info
+nak_xfb_from_nir(const struct nir_xfb_info *nir_xfb)
+{
+   if (nir_xfb == NULL)
+      return (struct nvk_xfb_info) { };
+
+   struct nvk_xfb_info nak_xfb = { };
+
+   u_foreach_bit(b, nir_xfb->buffers_written) {
+      nak_xfb.stride[b] = nir_xfb->buffers[b].stride;
+      nak_xfb.stream[b] = nir_xfb->buffer_to_stream[b];
+   }
+
+   for (unsigned o = 0; o < nir_xfb->output_count; o++) {
+      const nir_xfb_output_info *out = &nir_xfb->outputs[o];
+      const uint8_t b = out->buffer;
+      assert(nir_xfb->buffers_written & BITFIELD_BIT(b));
+
+      const uint16_t attr_addr = nak_varying_attr_addr(out->location);
+      assert(attr_addr % 4 == 0);
+      const uint16_t attr_idx = attr_addr / 4;
+
+      assert(out->offset % 4 == 0);
+      uint8_t out_idx = out->offset / 4;
+
+      u_foreach_bit(c, out->component_mask)
+         nak_xfb.attr_index[b][out_idx++] = attr_idx + c;
+
+      nak_xfb.attr_count[b] = MAX2(nak_xfb.attr_count[b], out_idx);
+   }
+
+   return nak_xfb;
+}
+
 static nir_def *
 load_frag_w(nir_builder *b, nir_def *bary)
 {

src/nouveau/compiler/nak_private.h

@@ -22,6 +22,9 @@ struct nak_compiler {
    struct nir_shader_compiler_options nir_options;
 };
 
+struct nvk_xfb_info
+nak_xfb_from_nir(const struct nir_xfb_info *nir_xfb);
+
 struct nak_io_addr_offset {
    nir_scalar base;
    int32_t offset;