Microprocessor designers such as Intel and AMD implement old instruction sets at their modern processors to ensure backward compatibility with legacy code. In addition to old back-ward compatibility instructions, new extensions are constantly introduced to add functionalities. In this way, the size of the IA-32 ISA is growing at a fast pace, reaching almost 1300 different instructions in 2013 with the introduction of AVX2 and FMA3 by Haswell. Increasing the size of the ISA impacts both hardware and software: it costs a complex microprocessor front- end design, which requires more silicon area, consumes more energy and demands more hardware debugging efforts; it also hinders software performance, since in IA-32 newer instructions are bigger and take up more space in the instruction cache. In this work, after analyzing x86 code from 3 different Windows versions and its respective contemporary applications plus 3 Linux distributions, from 1995 to 2012, we found that up to 30 classes of instructions get unused with time in these software. Should modern x86 processors sacrifice efficiency to provide strict conformance with old software from 30 years ago? Our results show that many old instructions may be truly retired.

Slides for the presentation can be downloaded here. Besides WIVOSCA, the AMAS-BT workshop on Binary Translation also had great talks. Moving from the workshops to the ISCA conference itself, there was an amazing talk entitled DNA-based Molecular Architecture with Spatially Localized Components, which totally twisted my mind regarding the emerging technologies topic. The conference isn’t over yet and I hope to attend more break-through research talks in the next few days.