r600/sfn: assert on use of abs modifier in op3

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18983>

src/gallium/drivers/r600/sfn/sfn_instr_alu.cpp

@@ -1925,6 +1925,10 @@ static bool emit_alu_op3(const nir_alu_instr& alu, EAluOp opcode, Shader& shader
          if (src[1]->negate) ir->set_alu_flag(alu_src1_neg);
          if (src[2]->negate) ir->set_alu_flag(alu_src2_neg);
 
+         assert(!src[0]->abs);
+         assert(!src[1]->abs);
+         assert(!src[2]->abs);
+
          if (alu.dest.saturate) ir->set_alu_flag(alu_dst_clamp);
          ir->set_alu_flag(alu_write);
          shader.emit_instruction(ir);