Dec. 2, 2022
8:32 p.m.
On Fri Dec 2 20:30:47 2022 +0000, **** wrote: > Paul Gofman replied on the mailing list: > ``` > On 12/2/22 14:25, Gabriel Ivăncescu (@insn) wrote: > > On Fri Dec 2 18:57:30 2022 +0000, Jacek Caban wrote: > >>> This should help a bit more, does it make a difference for you? > >> My previous test wasn't really good for measuring it. > >> I hacked a micro-benchmark, which confirms that the patch improves > >> performance a lot. It was visible when doing "real" Vulkan > >> vkGetPhysicalDeviceProperties calls in a loop, but even cleaner when I > >> changed it further to make Unix side to be no-op. It closes most of the > >> gap between direct call and __wine_unix_call_dispatcher. Times recorded > >> for no-op calls: > >> - direct call: 5761 > >> - unpatched Wine: 13933 > >> - ret.diff: 6823 (55% time spent in __wine_unix_call_dispatcher, 29% in > >> PE vkGetPhysicalDeviceProperties) > >> Looks impressive! > > @gofman This isn't about setting it in rcx or not, it's about > mispairing `call`s and `ret`s, which basically means 100% mispredicted > because CPUs are optimized for it, so it couldn't do any speculative > execution past the return before. > > > Yes, I figured that much. Yet the attached diff removes the return > address from rcx in wine_syscall_dispatcher(), so I thought it makes > sense to note that it will break things. > ``` Would it help to return to the return address already on the PE stack? -- https://gitlab.winehq.org/wine/wine/-/merge_requests/1552#note_18480