pco: support flat interpolation varyings

Signed-off-by: Simon Perretta <simon.perretta@imgtec.com>
Acked-by: Frank Binns <frank.binns@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33998>

src/imagination/include/hwdef/rogue_hw_defs.h

@@ -165,6 +165,12 @@
 #define ROGUE_USRM_LINE_SIZE_PER_INSTANCE \
    (ROGUE_PDS_US_TEMP_ALLOCATION_GRANULARITY * ROGUE_USRM_LINE_SIZE)
 
-#define ROGUE_USC_COEFFICIENT_SET_SIZE 4U
+enum {
+   ROGUE_USC_COEFFICIENT_SET_A = 0,
+   ROGUE_USC_COEFFICIENT_SET_B,
+   ROGUE_USC_COEFFICIENT_SET_C,
+   ROGUE_USC_COEFFICIENT_SET_PAD,
+   ROGUE_USC_COEFFICIENT_SET_SIZE,
+};
 
 #endif /* ROGUE_HW_DEFS_H */

src/imagination/pco/pco_nir.c

@@ -168,21 +168,33 @@ static uint8_t vectorize_filter(const nir_instr *instr, UNUSED const void *data)
 }
 
 /**
- * \brief Filters for a varying position load_input in frag shaders.
+ * \brief Filter for fragment shader inputs that need to be scalar.
  *
  * \param[in] instr Instruction.
  * \param[in] data User data.
  * \return True if the instruction was found.
  */
-static bool frag_pos_filter(const nir_instr *instr, UNUSED const void *data)
+static bool frag_in_scalar_filter(const nir_instr *instr, const void *data)
 {
    assert(instr->type == nir_instr_type_intrinsic);
+   nir_shader *nir = (nir_shader *)data;
 
    nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
    if (intr->intrinsic != nir_intrinsic_load_input)
       return false;
 
-   return nir_intrinsic_io_semantics(intr).location == VARYING_SLOT_POS;
+   gl_varying_slot location = nir_intrinsic_io_semantics(intr).location;
+   if (location == VARYING_SLOT_POS)
+      return true;
+
+   nir_variable *var =
+      nir_find_variable_with_location(nir, nir_var_shader_in, location);
+   assert(var);
+
+   if (var->data.interpolation == INTERP_MODE_FLAT)
+      return true;
+
+   return false;
 }
 
 /**
@@ -285,8 +297,8 @@ void pco_lower_nir(pco_ctx *ctx, nir_shader *nir, pco_data *data)
                nir,
                nir_lower_io_to_scalar,
                nir_var_shader_in,
-               frag_pos_filter,
-               NULL);
+               frag_in_scalar_filter,
+               nir);
    }
 
    do {

src/imagination/pco/pco_trans_nir.c

@@ -355,6 +355,15 @@ trans_load_input_fs(trans_ctx *tctx, nir_intrinsic_instr *intr, pco_ref dest)
                                              .itr_mode = itr_mode);
    }
 
+   case INTERP_MODE_FLAT: {
+      pco_ref coeff_c =
+         pco_ref_hwreg(coeffs_index + ROGUE_USC_COEFFICIENT_SET_C,
+                       PCO_REG_CLASS_COEFF);
+
+      assert(chans == 1);
+      return pco_mov(&tctx->b, dest, coeff_c);
+   }
+
    case INTERP_MODE_NOPERSPECTIVE:
       return usc_itrsmp_enhanced ? pco_ditr(&tctx->b,
                                             dest,