From: Iago Toral Quiroga <ito...@igalia.com>
When we are actually creating a double using values obtained from a
previous unpack operation we can bypass the unpack and source from
the original double value directly.
---
src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index ca1f24f..4332575 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -1091,6 +1091,29 @@ fs_visitor::nir_emit_alu(const fs_builder &bld,
nir_alu_instr *instr)
break;
case nir_op_pack_double_2x32_split:
+ /* Optimize the common case where we are re-packing a double with
+ * the result of a previous double unpack. In this case we can take the
+ * 32-bit value to use in the re-pack from the original double and bypass
+ * the unpack operation.
+ */
+ for (int i = 0; i < 2; i++) {
+ if (instr->src[i].src.is_ssa) {
+ nir_instr *parent_instr = instr->src[i].src.ssa->parent_instr;
+ if (parent_instr->type == nir_instr_type_alu) {
+ nir_alu_instr *alu_parent = nir_instr_as_alu(parent_instr);
+ if (alu_parent->op == nir_op_unpack_double_2x32_split_x ||
+ alu_parent->op == nir_op_unpack_double_2x32_split_y) {
+ op[i] = get_nir_src(alu_parent->src[0].src);
+ op[i] = offset(retype(op[i], BRW_REGISTER_TYPE_DF), bld,
+ alu_parent->src[0].swizzle[channel]);
+ op[i] = retype(op[i], BRW_REGISTER_TYPE_UD);
+ if (alu_parent->op == nir_op_unpack_double_2x32_split_y)
+ op[i] = horiz_offset(op[i], 1);
+ op[i] = stride(op[i], 2);
+ }
+ }
+ }
+ }
bld.emit(FS_OPCODE_PACK, result, op[0], op[1]);
break;
--
2.5.0
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