nir/xfb_info: add new fields to describe 16-bit XFB better

for drivers that need this information

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35256>

src/compiler/nir/nir_gather_xfb_info.c

@@ -348,7 +348,11 @@ nir_gather_xfb_info_from_intrinsics(nir_shader *nir)
                out.component_mask =
                   BITFIELD_RANGE(index, xfb.out[index % 2].num_components);
                out.location = sem.location;
+               out.data_is_16bit = intr->src[0].ssa->bit_size == 16;
                out.high_16bits = sem.high_16bits;
+               out.mediump = sem.medium_precision;
+               out.mediump_upconvert_type = nir_intrinsic_src_type(intr) &
+                                            (nir_type_float | nir_type_int | nir_type_uint);
                out.buffer = xfb.out[index % 2].buffer;
                out.offset = (uint32_t)xfb.out[index % 2].offset * 4;
                util_dynarray_append(&array, nir_xfb_output_info, out);

src/compiler/nir/nir_xfb_info.h

@@ -44,7 +44,10 @@ typedef struct {
    uint8_t buffer;
    uint16_t offset;
    uint8_t location;
-   bool high_16bits;
+   bool data_is_16bit;  /* whether the src data has bit_size=16 */
+   bool high_16bits;    /* whether the src data comes from high 16 bits */
+   bool mediump;        /* whether 16-bit data must be upconverted to 32 bits before memory stores */
+   nir_alu_type mediump_upconvert_type; /* the type of upconversion (float, int, or uint) */
    uint8_t component_mask;
    uint8_t component_offset;
 } nir_xfb_output_info;