From: Heiko Stuebner <heiko.stuebner@xxxxxxxx> The Zbb extension can be used to make string functions run a lot faster. To allow There are essentially two problems to solve: - making it possible for str* functions to replace what they do in a performant way This is done by inlining the core functions and then using alternatives to call the actual variant. This of course will need a more intelligent selection mechanism down the road when more variants may exist using different available extensions. - actually allowing calls in alternatives Function calls use auipc + jalr to reach those 32bit relative addresses but when they're compiled the offset will be wrong as alternatives live in a different section. So when the patch gets applied the address will point to the wrong location. So similar to arm64 the target addresses need to be updated. This is probably also helpful for other things needing more complex code in alternatives. In my half-scientific test-case of running the functions in question on a 95 character string in a loop of 10000 iterations, the Zbb variants shave off around 2/3 of the original runtime. For v2 I got into some sort of cleanup spree for the general instruction parsing that already existed. A number of places do their own instruction parsing and I tried consolidating some of them. Noteable, the kvm parts still do, but I had to stop somewhere :-) The series is based on v6.1-rc7 right now. changes since v2: - add patch fixing the c.jalr funct4 value - reword some commit messages - fix position of auipc addition patch (earlier) - fix compile errors from patch-reordering gone wrong (worked at the end of v2, but compiling individual patches caused issues) - patches are now tested individually - limit Zbb variants for GNU as for now (LLVM support for .option arch is still under review) - prevent str-functions from getting optimized to builtin-variants changes since v1: - a number of generalizations/cleanups for instruction parsing - use accessor function to access instructions (Emil) - actually patch the correct location when having more than one instruction in an alternative block - string function cleanups (comments etc) (Conor) - move zbb extension above s* extensions in cpu.c lists changes since rfc: - make Zbb code actually work - drop some unneeded patches - a lot of cleanups Heiko Stuebner (14): RISC-V: fix funct4 definition for c.jalr in parse_asm.h RISC-V: add prefix to all constants/macros in parse_asm.h RISC-V: detach funct-values from their offset RISC-V: add ebreak instructions to definitions RISC-V: add auipc elements to parse_asm header RISC-V: Move riscv_insn_is_* macros into a common header RISC-V: rename parse_asm.h to insn.h RISC-V: kprobes: use central defined funct3 constants RISC-V: add U-type imm parsing to insn.h header RISC-V: add rd reg parsing to insn.h header RISC-V: fix auipc-jalr addresses in patched alternatives efi/riscv: libstub: mark when compiling libstub RISC-V: add infrastructure to allow different str* implementations RISC-V: add zbb support to string functions arch/riscv/Kconfig | 24 ++ arch/riscv/Makefile | 3 + arch/riscv/include/asm/alternative.h | 3 + arch/riscv/include/asm/errata_list.h | 3 +- arch/riscv/include/asm/hwcap.h | 1 + arch/riscv/include/asm/insn.h | 292 +++++++++++++++++++++++ arch/riscv/include/asm/parse_asm.h | 219 ----------------- arch/riscv/include/asm/string.h | 83 +++++++ arch/riscv/kernel/alternative.c | 72 ++++++ arch/riscv/kernel/cpu.c | 1 + arch/riscv/kernel/cpufeature.c | 29 ++- arch/riscv/kernel/image-vars.h | 6 +- arch/riscv/kernel/kgdb.c | 63 ++--- arch/riscv/kernel/probes/simulate-insn.c | 19 +- arch/riscv/kernel/probes/simulate-insn.h | 26 +- arch/riscv/lib/Makefile | 6 + arch/riscv/lib/strcmp.S | 38 +++ arch/riscv/lib/strcmp_zbb.S | 96 ++++++++ arch/riscv/lib/strlen.S | 29 +++ arch/riscv/lib/strlen_zbb.S | 115 +++++++++ arch/riscv/lib/strncmp.S | 41 ++++ arch/riscv/lib/strncmp_zbb.S | 112 +++++++++ drivers/firmware/efi/libstub/Makefile | 2 +- 23 files changed, 982 insertions(+), 301 deletions(-) create mode 100644 arch/riscv/include/asm/insn.h delete mode 100644 arch/riscv/include/asm/parse_asm.h create mode 100644 arch/riscv/lib/strcmp.S create mode 100644 arch/riscv/lib/strcmp_zbb.S create mode 100644 arch/riscv/lib/strlen.S create mode 100644 arch/riscv/lib/strlen_zbb.S create mode 100644 arch/riscv/lib/strncmp.S create mode 100644 arch/riscv/lib/strncmp_zbb.S -- 2.35.1
