On 3/29/22 03:47, Ammar Faizi wrote: > The asm constraint does not reflect that the asm statement can modify > the value of @loops. But the asm statement in delay_loop() does modify > the @loops. > > Specifiying the wrong constraint may lead to undefined behavior, it may > clobber random stuff (e.g. local variable, important temporary value in > regs, etc.). This is especially dangerous when the compiler decides to > inline the function and since it doesn't know that the value gets > modified, it might decide to use it from a register directly without > reloading it. > > Fix this by changing the constraint from "a" (as an input) to "+a" (as > an input and output). Was this found by inspection or was it causing real-world problems?
