On Sun, Dec 9, 2012 at 2:50 PM, Uros Bizjak <ubiz...@gmail.com> wrote: > Hello! > >> I noticed in prologue/epilogue, GCC prefers to use MOVs followed by a >> SP adjustment instead of a sequence of pushes/pops. The preference to >> the MOVs are good for old CPU micro-architectures (before pentium-4, >> K10), because it breaks the data dependency. In modern >> micro-architecture, push/pop is implemented using a mechanism called >> stack engine. The data dependency is removed by the hardware, and >> push/pop becomes very cheap (1 uOp, 1 cycle latency), and they are >> smaller. There is no longer the need to avoid using them. This is >> also what ICC does. > >> 2012-12-08 Xinliang David Li <davi...@google.com> >> * config/i386/i386.c: Eanble push/pop in pro/epilogue for moderen >> CPUs. > > s/moderen/modern > > OK for mainline SVN.
It's also more costly for unwind info in the prologue/epilogue. Thus, did you measure the effect on CFI size? Thanks, Richard. > Thanks, > Uros.
