On Tue, Nov 15, 2022 at 8:53 AM Palmer Dabbelt <pal...@dabbelt.com> wrote: > > On Mon, 14 Nov 2022 16:46:37 PST (-0800), Kito Cheng wrote: > > Hi Christoph: > > > >> This patch implements expansions for the cmpstrsi and the cmpstrnsi > >> builtins using Zbb instructions (if available). > >> This allows to inline calls to strcmp() and strncmp(). > >> > >> The expansion basically emits a peeled comparison sequence (i.e. a peeled > >> comparison loop) which compares XLEN bits per step if possible. > >> > >> The emitted sequence can be controlled, by setting the maximum number > >> of compared bytes (-mstring-compare-inline-limit). > > > > I would like to have a unified option interface, > > maybe -m[no-]inline-str[n]cmp and -minline-str[n]cmp-limit. > > And add some option like this: > > -minline-str[n]cmp=[bitmanip|vector|auto] in future, > > since I assume we'll have different versions of those things. > > Can we just decide that from mtune? We'll probably have uarch-specific > string functions at some point, might as well start planning for it now.
I assume you mean the -minline-str[n]cmp=[bitmanip|vector|auto] part? I think this part should have more discussion and could defer that until we reach consensus. But -m[no-]inline-str[n]cmp and -minline-str[n]cmp-limit part I favor having those two options to disable and/or fine tune those parameters. > > >> gcc/ChangeLog: > >> > >> * config/riscv/riscv-protos.h (riscv_expand_strn_compare): New > >> prototype. > >> * config/riscv/riscv-string.cc (GEN_EMIT_HELPER3): New helper > >> macros. > >> (GEN_EMIT_HELPER2): New helper macros. > >> (expand_strncmp_zbb_sequence): New function. > >> (riscv_emit_str_compare_zbb): New function. > >> (riscv_expand_strn_compare): New function. > >> * config/riscv/riscv.md (cmpstrnsi): Invoke expansion functions > >> for strn_compare. > >> (cmpstrsi): Invoke expansion functions for strn_compare. > >> * config/riscv/riscv.opt: Add new parameter > >> '-mstring-compare-inline-limit'. > > > > We need to document this option.
