SSBO loads were using byte_scattered read messages as they allow
reading 16-bit size components. byte_scattered messages can only
operate one component at a time so we needed to emit as many messages
as components.
But for vec2 and vec4 of 16-bit, being multiple of 32-bit we can use the
untyped_surface_read message to read pairs of 16-bit components using
only one message. Once each pair is read it is unshuffled to return the
proper 16-bit components. vec3 case is assimilated to vec4 but the 4th
component is ignored.
16-bit scalars are read using one byte_scattered_read message.
v2: Removed use of stride = 2 on sources (Jason Ekstrand)
Rework optimization using unshuffle 16 reads (Chema Casanova)
v3: Use W and D types insead of HF and F in shuffle to avoid rounding
erros (Jason Ekstrand)
Use untyped_surface_read for 16-bit vec3. (Jason Ekstrand)
CC: Jason Ekstrand <ja...@jlekstrand.net>
---
src/intel/compiler/brw_fs_nir.cpp | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/src/intel/compiler/brw_fs_nir.cpp
b/src/intel/compiler/brw_fs_nir.cpp
index e11e75e6332..8deec082d59 100644
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -2303,16 +2303,31 @@ do_untyped_vector_read(const fs_builder &bld,
unsigned num_components)
{
if (type_sz(dest.type) <= 2) {
- fs_reg read_offset = bld.vgrf(BRW_REGISTER_TYPE_UD);
- bld.MOV(read_offset, offset_reg);
- for (unsigned i = 0; i < num_components; i++) {
- fs_reg read_reg =
- emit_byte_scattered_read(bld, surf_index, read_offset,
+ assert(dest.stride == 1);
+
+ if (num_components > 1) {
+ /* Pairs of 16-bit components can be read with untyped read, for
16-bit
+ * vec3 4th component is ignored.
+ */
+ fs_reg read_result =
+ emit_untyped_read(bld, surf_index, offset_reg,
+ 1 /* dims */, DIV_ROUND_UP(num_components, 2),
+ BRW_PREDICATE_NONE);
+ shuffle_32bit_load_result_to_16bit_data(bld,
+ retype(dest, BRW_REGISTER_TYPE_W),
+ retype(read_result, BRW_REGISTER_TYPE_D),
+ num_components);
+ } else {
+ assert(num_components == 1);
+ /* scalar 16-bit are read using one byte_scattered_read message */
+ fs_reg read_result =
+ emit_byte_scattered_read(bld, surf_index, offset_reg,
1 /* dims */, 1,
type_sz(dest.type) * 8 /* bit_size */,
BRW_PREDICATE_NONE);
- bld.MOV(offset(dest, bld, i), subscript(read_reg, dest.type, 0));
- bld.ADD(read_offset, read_offset, brw_imm_ud(type_sz(dest.type)));
+ read_result.type = dest.type;
+ read_result.stride = 2;
+ bld.MOV(dest, read_result);
}
} else if (type_sz(dest.type) == 4) {
fs_reg read_result = emit_untyped_read(bld, surf_index, offset_reg,
--
2.11.0
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