On Mon, Jan 10, 2022 at 8:28 AM Iain Sandoe <i...@sandoe.co.uk> wrote: > > Hi Florian, > > > On 10 Jan 2022, at 08:38, Florian Weimer <fwei...@redhat.com> wrote: > > > > * Jeff Law via Gcc: > > > >> Most targets these days use registers for parameter passing and > >> obviously we can run out of registers on all of them. The key > >> property is the size/alignment of the argument differs depending on if > >> it's pass in a register (get promoted) or passed in memory (not > >> promoted). I'm not immediately aware of another ABI with that > >> feature. Though I haven't really gone looking. > > > > I think what AArch64 Darwin does is not compatible with a GCC extension > > that allows calling functions defined with a prototype without it (for > > pre-ISO-C compatibility). > > AFAIU the implementation: > > In the case that a call is built and no prototype is available, the > assumption is > that all parms are named. The promotion is then done according to the C > promotion rules. > > [for the number of args that can be passed in int regs] the callee will > happen to > observe the same rules in this case. > > It will, however, break once we overflow the number of int regs.. :/ > > ==== > > The case that is fundamentally broken from scratch is of a variadic function > called without a prototype - since the aarch64-darwin ABI places unnamed > parms differently. > > So that the absence of a prototype causes us to place all args as if they were > named. > > ==== > > Wmissing-prototype > Wstrict-prototypes > > would wisely be promoted to errors for this platform,
Relevant bugs in this area: 82922, add -Wstrict-prototypes to -Wextra: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82922 91092, Error on implicit function declarations by default: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91092 (and the related bugs in the "See Also", "Depends On", "Duplicates", etc. fields for each of them) > > (the ABI is obviously not up for change, since it’s already on millions of > devices). > > > Given that, anyone defining an ABI in > > parallel with a GCC implementation probably has paused, reconsidered > > what they were doing, > > My guess is that this step was omitted - i.e. the port was designed in the > LLVM > framework. I can raise a query with the ABI owners, I guess. > > > and adjusted the ABI for K&R compatibility. > > FWIW, we bootstrap sucessfully including the K&R code in intl/ > Given we have 8 int regs available, probably many calls will work .. > > ==== > > As of now, I must assume that what is broken by the cases above will remain > broken, and I just need to find a way to implement the cases that will work > (i.e. > when proper prototypes are available) > > thanks > Iain >
