We used the byte_scattered_read message because it allows to read from
non aligned 32-bit offsets. We were reading one component for each
message.
Using a 32-bit bitsize read at byte_scattered_read we can read up to two
16-bit components or four 8-bit components with only one message per
iteration.
The same applies for 16-bit bitsize for two 8-bit components read. In
the case of int8 vec3, we read them as 32-bit and we ignore the padding.
Cc: Jason Ekstrand <ja...@jlekstrand.net>
---
src/intel/compiler/brw_fs_nir.cpp | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/src/intel/compiler/brw_fs_nir.cpp
b/src/intel/compiler/brw_fs_nir.cpp
index 9b11b5fbd01..a1f946708ed 100644
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -2415,24 +2415,34 @@ do_untyped_vector_read(const fs_builder &bld,
num_components);
} else {
fs_reg read_offset = bld.vgrf(BRW_REGISTER_TYPE_UD);
- for (unsigned i = 0; i < num_components; i++) {
- if (i == 0) {
+ unsigned iters = DIV_ROUND_UP(type_sz(dest.type) * num_components, 4);
+ for (unsigned it = 0; it < iters; it++) {
+ if (it == 0) {
bld.MOV(read_offset, offset_reg);
} else {
- bld.ADD(read_offset, offset_reg,
- brw_imm_ud(i * type_sz(dest.type)));
+ bld.ADD(read_offset, offset_reg, brw_imm_ud(4 * it));
}
+ unsigned iter_components = MIN2(4 / type_sz(dest.type),
+ num_components);
+ num_components -= iter_components;
+ /* We adjust the bitsize_read to hold as many components we can in
+ * the same read message. We use 32-bit to read 8-bit vec3 but we
+ * ignore last padding.component.
+ */
+ unsigned bitsize_read = util_next_power_of_two(8 * iter_components
*
+ type_sz(dest.type));
/* Non constant offsets are not guaranteed to be aligned 32-bits
- * so they are read using one byte_scattered_read message
- * for each component.
+ * for 8/16 bit componentes. We use byte_scattered_read for
+ * one or multiple components up to 4-bytes for iteration.
*/
fs_reg read_result =
emit_byte_scattered_read(bld, surf_index, read_offset,
1 /* dims */, 1,
- type_sz(dest.type) * 8 /* bit_size */,
+ bitsize_read,
BRW_PREDICATE_NONE);
- bld.MOV(offset(dest, bld, i),
- subscript (read_result, dest.type, 0));
+ shuffle_from_32bit_read(bld, offset(dest, bld,
+ it * 4 / type_sz(dest.type)),
+ read_result, 0, iter_components);
}
}
} else if (type_sz(dest.type) == 4) {
--
2.17.1
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