Zbb string optimizations and call support in alternatives
From: Heiko Stuebner <heiko.stuebner@...> Date: Thu, 10 Nov 2022 17:27:20 +0100
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. changes since rfc: - make Zbb code actually work - drop some unneeded patches - a lot of cleanups Heiko Stuebner (7): efi/riscv: libstub: mark when compiling libstub RISC-V: add auipc elements to parse_asm header RISC-V: add U-type imm parsing to parse_asm header RISC-V: add rd reg parsing to parse_asm header RISC-V: fix auipc-jalr addresses in patched alternatives RISC-V: add infrastructure to allow different str* implementations RISC-V: add zbb support to string functions arch/riscv/Kconfig | 23 ++++++ arch/riscv/include/asm/errata_list.h | 3 +- arch/riscv/include/asm/hwcap.h | 1 + arch/riscv/include/asm/parse_asm.h | 21 +++++ arch/riscv/include/asm/string.h | 83 ++++++++++++++++++++ arch/riscv/kernel/cpu.c | 1 + arch/riscv/kernel/cpufeature.c | 97 ++++++++++++++++++++++- arch/riscv/kernel/image-vars.h | 6 +- arch/riscv/lib/Makefile | 6 ++ arch/riscv/lib/strcmp.S | 39 ++++++++++ arch/riscv/lib/strcmp_zbb.S | 91 ++++++++++++++++++++++ arch/riscv/lib/strlen.S | 29 +++++++ arch/riscv/lib/strlen_zbb.S | 98 ++++++++++++++++++++++++ arch/riscv/lib/strncmp.S | 41 ++++++++++ arch/riscv/lib/strncmp_zbb.S | 106 ++++++++++++++++++++++++++ drivers/firmware/efi/libstub/Makefile | 2 +- 16 files changed, 640 insertions(+), 7 deletions(-) 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
Patches in this set
- [0001] efi/riscv: libstub: mark when compiling libstub (raw)
- [0002] RISC-V: add auipc elements to parse_asm header (raw)
- [0003] RISC-V: add U-type imm parsing to parse_asm header (raw)
- [0004] RISC-V: add rd reg parsing to parse_asm header (raw)
- [0005] RISC-V: fix auipc-jalr addresses in patched alternatives (raw)
- [0006] RISC-V: add infrastructure to allow different str* (raw)
- [0007] RISC-V: add zbb support to string functions (raw)
Statistics
- 7 individual patches
- 646 lines added
- 13 lines removed