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================ Comment at: clang/lib/CodeGen/TargetInfo.cpp:2804 + return; + } + ---------------- Quuxplusone wrote: > Asking silly questions because I don't stand a chance of understanding either > the code or the tests... > > In the x86-64 ABI, an ordinary 16-byte `struct` would be passed in `rdi/rsi` > and returned in `rdx/rax`. An ordinary 17-byte `struct` would be passed by > hidden reference and returned by hidden reference. > > Is your intent here that `_ExtInt` will follow the same convention, i.e., > `_ExtInt(128)` will be passed in `rdi/rsi` and returned in `rdx/rax`? and > `_ExtInt(129)` will be passed and returned by hidden reference? > > Clang trunk currently passes `_ExtInt(256)` in `rdi/rsi/rdx/rcx/r8/r9/stack` > as if it were a series of `uint64_t`s. (I hadn't noticed until now.) That's > kind of cute. Is the current PR motivated by performance concerns with the > multi-`uint64_t` approach, or just trying to be consistent with the `struct` > rules? Yes, that is my intent. The bug you filed apparently showed why putting it in registers is perhaps a bad idea (for something that large), AND gets us more consistent with structs. As there is no official ABI for any of the 3 platforms, this seems more consistent and gives performance benefit. @craig.topper can explain this part better than me. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D78785/new/ https://reviews.llvm.org/D78785 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
