On 14.02.2024 16:02, Roger Pau Monné wrote: > On Wed, Feb 14, 2024 at 10:35:58AM +0000, Frediano Ziglio wrote: >> We just pushed a 8-bytes zero and exception constants are >> small so we can just write a single byte saving 3 bytes for >> instruction. >> With ENDBR64 this reduces the size of many entry points from 32 to >> 16 bytes (due to alignment). >> Similar code is already used in autogen_stubs. > > Will using movb instead of movl have any performance impact? I don't > think we should trade speed for code size, so this needs to be > mentioned in the commit message.
That's really what the last sentence is about (it could have been said more explicitly though): If doing so on interrupt paths is fine, it ought to be fine on exception paths as well. Plus, no matter what, we have two overlapping stores in every one of these places. But yes, their sizes may still be relevant to the overall result. Jan
