F ree R ider

Abstract

Short-vector S imd and D sp instructions are popular extensions to common I sa s. These extensions deliver excellent performance and compact code for some compute-intensive applications, but they require specialized compiler support. To enable the programmer to explicitly request the use of such an instruction, many C compilers provide platform-specific intrinsic functions, whose implementation is handled specially by the compiler. The use of such intrinsics, however, inevitably results in nonportable code. In this article, we develop a novel methodology for retargeting such nonportable code, which maps intrinsics from one platform to another, taking advantage of similar intrinsics on the target platform. We employ a description language to specify the signature and semantics of intrinsics and perform graph-based pattern matching and high-level code transformations to derive optimized implementations exploiting the target’s intrinsics, wherever possible. We demonstrate the effectiveness of our new methodology, implemented in the F ree R ider tool, by automatically retargeting benchmarks derived from O pen CV samples and a complex embedded application optimized to run on an A rm C ortex -M4 to an I ntel E dison module with S se 4.2 instructions (and vice versa). We achieve a speedup of up to 3.73 over a plain C baseline, and on average 96.0% of the speedup of manually ported and optimized versions of the benchmarks.