Performance impact of -fno-strict-aliasing

Question

Is there any study or set of benchmarks showing the performance degradation due to specifying -fno-strict-aliasing in GCC (or equivalent in other compilers)?

Answer 1

What I can tell you from experience (having tested this with a large project on PS3, PowerPC being an architecture that due to it's many registers can actually benefit from SA quite well) is that the optimizations you're going to see are generally going to be very local (scope wise) and small. On a 20MB executable it scraped off maybe 80kb of the .text section (= code) and this was all in small scopes & loops.

This option can make your generated code a bit more lightweight and optimized than it is right now (think in the 1 to 5 percent range), but do not expect any big results. Hence, the effect of using -fno-strict-aliasing is probably not going to be a big influence on your performance, at all. That said, having code that requires -fno-strict-aliasing is a suboptimal situation at best.