Would it be possible to mark the JO instruction (jump-if-overflow) as unlikely, so that the CPU would always predict the branch to not be taken, without consuming one branch prediction slot?
> so that the CPU would always predict the branch to not be taken
AFAIK there isn't any notion of likely/unlikely in object code on most CPU architectures. I'm only really familiar with x86 and ARM though.
__builtin_expect() in GCC (the "likely()" and "unlikely()" macros in the Linux kernel use this) can do a lot of things to optimize branches, like prefetch instructions and decide whether or not the jump should be the usually taken or usually not taken side, but it can't actually emit instructions that directly tell the CPU "always predict this" AFAIK.
AFAIK there isn't any notion of likely/unlikely in object code on most CPU architectures. I'm only really familiar with x86 and ARM though.
__builtin_expect() in GCC (the "likely()" and "unlikely()" macros in the Linux kernel use this) can do a lot of things to optimize branches, like prefetch instructions and decide whether or not the jump should be the usually taken or usually not taken side, but it can't actually emit instructions that directly tell the CPU "always predict this" AFAIK.