LLHD: A Multi-level Intermediate Representation for Hardware Description Languages

Modern Hardware Description Languages (HDLs) such as SystemVerilog or VHDL are, due to their sheer complexity, insufficient to transport designs through modern circuit design flows. Instead, each design automation tool lowers HDLs to its own Intermediate Representation (IR). These tools are monolithic and mostly proprietary, disagree in their implementation of HDLs, and while many redundant IRs exists, no IR today can be used through the entire circuit design flow. To solve this problem, we propose the LLHD multi-level IR. LLHD is designed as simple, unambiguous reference description of a digital circuit, yet fully captures existing HDLs. We show this with our reference compiler on designs as complex as full CPU cores. LLHD comes with lowering passes to a hardware-near structural IR, which readily integrates with existing tools. LLHD establishes the basis for innovation in HDLs and tools without redundant compilers or disjoint IRs. For instance, we implement an LLHD simulator that runs up to 2.4x faster than commercial simulators but produces equivalent, cycle-accurate results. An initial vertically-integrated research prototype is capable of representing all levels of the IR, implements lowering from the behavioural to the structural IR, and covers a sufficient subset of SystemVerilog to support a full CPU design

Environmental Education After Sustainability : Hope in the Midst of Tragedy

In this article, I discuss the challenge posed to environmental education (EE; and education for sustainable development) by the thinkers who see the situation of the world as so severe that ‘sustainability’ is an outdated concept. My approach is interdisciplinary and I discuss especially the connections between EE and eco-psychology. Based on psychological research, I argue that the wide-scale unconscious anxiety, which people experience, should be taken very seriously in EE. My discussion thus contributes in a new kind of way to a long-standing key issue in EE, the gap between people’s values and the perceived action. Scholars of eco-anxiety have argued that instead of not caring, many people in fact care too much, and have to resort to psychological defenses of denial and disavowal. Thus, the question in EE is not anymore whether EE should deal with anxiety, for anxiety is already there. The prevailing attitude in EE writing is right in emphasizing positive matters and empowerment, but the relation between hope and optimism must be carefully thought about and a certain sense of tragedy must be included. Therefore, my article participates in the discussion about the role of ‘fear appeals’ in EE. My discussion is directed to anyone who wants to understand the reasons for inaction and the ways in which these may be overcome.Peer reviewe