https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70220
--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> --- (In reply to Wink Saville from comment #5) > > > > Compiler doesn't use segment registers, except for TLS, which should > > be used in ISR. ISR needs to save and restore any registers, which > > aren't used by compilers, if they are changed in ISR. > > Is there a definitive list of the registers that the compiler uses and their > purpose? I did some searches but didn't come up with any good answers. Compiler will preserve integer, FP, vector registers as well as MXCSR register, x87 FPU and MMX register state. If you change RSP or RBP in asm statement, you have to restore them.
