From 830d6de9ffca4791f28d8af88cf034e286990824 Mon Sep 17 00:00:00 2001
From: Georg Lehmann <dadschoorse@gmail.com>
Date: Sat, 13 Dec 2025 15:03:32 +0100
Subject: [PATCH] aco/isel: optimize pack_32_2x16_split(undef, const)
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Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39412>
---
 .../compiler/instruction_selection/aco_select_nir_alu.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/amd/compiler/instruction_selection/aco_select_nir_alu.cpp b/src/amd/compiler/instruction_selection/aco_select_nir_alu.cpp
index b400a49073a..ffbaab95a57 100644
--- a/src/amd/compiler/instruction_selection/aco_select_nir_alu.cpp
+++ b/src/amd/compiler/instruction_selection/aco_select_nir_alu.cpp
@@ -3139,8 +3139,12 @@ visit_alu_instr(isel_context* ctx, nir_alu_instr* instr)
       } else if (nir_src_is_undef(instr->src[1].src)) {
          bld.copy(Definition(dst), src0);
       } else if (nir_src_is_undef(instr->src[0].src)) {
-         bld.pseudo(aco_opcode::p_insert, Definition(dst), bld.def(s1, scc), src1, Operand::c32(1),
-                    Operand::c32(16));
+         if (nir_src_is_const(instr->src[1].src)) {
+            bld.copy(Definition(dst), Operand::c32(nir_src_as_uint(instr->src[1].src) << 16));
+         } else {
+            bld.pseudo(aco_opcode::p_insert, Definition(dst), bld.def(s1, scc), src1,
+                       Operand::c32(1), Operand::c32(16));
+         }
       } else if (ctx->program->gfx_level >= GFX9) {
          bld.sop2(aco_opcode::s_pack_ll_b32_b16, Definition(dst), src0, src1);
       } else {