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.
On 16-bit scalar and vec3 16-bit the not paired component is read using
only one byte_scattered_read message.
v2: Removed use of stride = 2 on sources (Jason Ekstrand)
Rework optimization using unshuffle 16 reads (Chema Casanova)
---
src/intel/compiler/brw_fs_nir.cpp | 37 ++++++++++++++++++++++++++++++-------
1 file changed, 30 insertions(+), 7 deletions(-)
diff --git a/src/intel/compiler/brw_fs_nir.cpp
b/src/intel/compiler/brw_fs_nir.cpp
index 774bd97968..332fc4bfb8 100644
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -2303,16 +2303,39 @@ do_untyped_vector_read(const fs_builder &bld,
bld.ADD(read_offset, read_offset, brw_imm_ud(16));
}
} else if (type_sz(dest.type) == 2) {
- for (unsigned i = 0; i < num_components; i++) {
+ assert(dest.stride == 1);
+
+ int component_pairs = num_components / 2;
+ /* Pairs of 16-bit components can be read with untyped read */
+ if (component_pairs > 0) {
+ fs_reg read_result = emit_untyped_read(bld, surf_index,
+ offset_reg,
+ 1 /* dims */,
+ component_pairs,
+ BRW_PREDICATE_NONE);
+ shuffle_32bit_load_result_to_16bit_data(bld,
+ retype(dest, BRW_REGISTER_TYPE_HF),
+ retype(read_result, BRW_REGISTER_TYPE_F),
+ component_pairs * 2);
+ }
+ /* Last component of vec3 and scalar 16-bit read needs to be read
+ * using one byte_scattered_read message
+ */
+ if (num_components % 2) {
fs_reg base_offset = bld.vgrf(BRW_REGISTER_TYPE_UD);
bld.ADD(base_offset,
offset_reg,
- brw_imm_ud(i * type_sz(dest.type)));
- fs_reg read_reg = emit_byte_scattered_read(bld, surf_index,
base_offset,
- 1 /* dims */,
- 1,
- BRW_PREDICATE_NONE);
- bld.MOV(offset(dest,bld,i), subscript(read_reg, dest.type, 0));
+ brw_imm_ud((num_components - 1) * type_sz(dest.type)));
+ fs_reg read_result = emit_byte_scattered_read(bld, surf_index,
+ base_offset,
+ 1 /* dims */,
+ 1,
+ BRW_PREDICATE_NONE);
+ read_result.type = dest.type;
+ read_result.stride = 2;
+
+ bld.MOV(offset(dest, bld, num_components - 1),
+ read_result);
}
} else {
unreachable("Unsupported type");
--
2.13.6
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