================ @@ -6007,10 +6007,13 @@ The user can call functions specified with the 'no_caller_saved_registers' attribute from an interrupt handler without saving and restoring all call-clobbered registers. -Functions specified with the 'no_caller_saved_registers' attribute should only +On X86, functions specified with the 'no_caller_saved_registers' attribute should only call other functions with the 'no_caller_saved_registers' attribute, or should be compiled with the '-mgeneral-regs-only' flag to avoid saving unused non-GPR registers. +On PowerPC, functions specified with the 'no_caller_saved_registers' attribute may not +return a value as the return register will be restored and thus cannot hold a value. ---------------- Luminyx1 wrote:
The intent was to allow for use cases where even modification of `r3` is considered intrusive (similar to an interrupt handler, but with a standard return routine such that `__attribute__((interrupt))` is not appropriate). What are the semantics of `preserve_most`/`preserve_all`? Would it be appropriate to implement `preserve_most` as saving general registers but not float registers (as x86 and ARM currently do), then `preserve_all` additionally saves float registers + the return register? https://github.com/llvm/llvm-project/pull/174320 _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
