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. > > 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.
