On Sun, Feb 14, 2021 at 06:59:11PM +0100, Philippe Mathieu-Daudé wrote: > Test BusyBox on the R5900 CPU with 2 different binaries: > > - o32 32-bit (statically linked) > - o32 64-bit (dynamically linked, uses multimedia instructions)
R5900/libc update: Gnu libc for o32 was merged some time ago so any recent Gentoo etc. will do fine without patches. For n32, there's a provisional patch that needs reworking to get merged (to have libc emulate DMULT etc. rather than the kernel/QEMU).[1] Musl has a pending patch I posted[2] about a month ago. Musl is o32 only, for all MIPS, but other than that it's got two significant advantages over Gnu libc: 1. excellent support for static linking; 2. program sizes are often much smaller, more than 5x smaller observed. An important detail is that since the R5900 FPU isn't compliant with the IEEE 754 standard[3] it's normally wholly emulated by either libc or the kernel, to comply with the MIPS psABI. The R5900 hardware FPU can perhaps be enabled with a future R5900 ELF ABI annotation extension.[4] Finally, the situation with the 128-bit R5900 general purpose registers (GPRs) is not fully resolved with the Linux kernel. The best case scenario, I believe, would be to have them available at all times.[5] Fredrik References: [1] https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg00974.html [2] https://www.openwall.com/lists/musl/2020/12/24/2 [3] https://github.com/frno7/linux/wiki/R5900-floating-point-unit-(FPU) [4] https://github.com/frno7/linux/issues/3 [5] https://github.com/frno7/linux/issues/5
