mirror of
https://github.com/rust-lang/rust.git
synced 2024-11-22 23:04:33 +00:00
2413f50a0b
[rustc_span][perf] Hoist lookup sorted by words out of the loop. ```@lqd``` commented on https://github.com/rust-lang/rust/pull/114351 asking if `sort_by_words(lookup)` is computed repeatedly. I was assuming that rustc should have no difficulties to hoist it automatically outside of the loop to avoid repeated pure computation, but according to https://godbolt.org/z/frs8Kj1rq it seems like I was wrong: original version seems to have 2 calls per loop iteration ``` .LBB16_3: mov rbx, qword ptr [r13] mov r14, qword ptr [r13 + 8] lea rdi, [rsp + 40] mov rsi, rbx mov rdx, r14 call example::sort_by_words lea rdi, [rsp + 64] mov rsi, qword ptr [rsp + 8] mov rdx, qword ptr [rsp + 16] call example::sort_by_words mov rdi, qword ptr [rsp + 40] mov rdx, qword ptr [rsp + 56] mov rsi, qword ptr [rsp + 64] cmp rdx, qword ptr [rsp + 80] mov qword ptr [rsp + 32], rdi mov qword ptr [rsp + 24], rsi jne .LBB16_5 call qword ptr [rip + bcmp@GOTPCREL] test eax, eax sete al mov dword ptr [rsp + 4], eax mov rsi, qword ptr [rsp + 72] test rsi, rsi jne .LBB16_8 jmp .LBB16_9 ``` but the manually hoisted version just 1: ``` .LBB16_3: mov r13, qword ptr [r15] mov r14, qword ptr [r15 + 8] lea rdi, [rsp + 64] mov rsi, r13 mov rdx, r14 call example::sort_by_words mov rdi, qword ptr [rsp + 64] mov rdx, qword ptr [rsp + 16] cmp qword ptr [rsp + 80], rdx mov qword ptr [rsp + 32], rdi jne .LBB16_5 mov rsi, qword ptr [rsp + 8] call qword ptr [rip + bcmp@GOTPCREL] test eax, eax sete bpl mov rsi, qword ptr [rsp + 72] test rsi, rsi jne .LBB16_8 jmp .LBB16_9 ``` This code is probably not very hot, but there is no reason to leave such a low hanging fruit. |
||
|---|---|---|
| .. | ||
| rustc | ||
| rustc_abi | ||
| rustc_arena | ||
| rustc_ast | ||
| rustc_ast_lowering | ||
| rustc_ast_passes | ||
| rustc_ast_pretty | ||
| rustc_attr | ||
| rustc_baked_icu_data | ||
| rustc_borrowck | ||
| rustc_builtin_macros | ||
| rustc_codegen_cranelift | ||
| rustc_codegen_gcc | ||
| rustc_codegen_llvm | ||
| rustc_codegen_ssa | ||
| rustc_const_eval | ||
| rustc_data_structures | ||
| rustc_driver | ||
| rustc_driver_impl | ||
| rustc_error_codes | ||
| rustc_error_messages | ||
| rustc_errors | ||
| rustc_expand | ||
| rustc_feature | ||
| rustc_fluent_macro | ||
| rustc_fs_util | ||
| rustc_graphviz | ||
| rustc_hir | ||
| rustc_hir_analysis | ||
| rustc_hir_pretty | ||
| rustc_hir_typeck | ||
| rustc_incremental | ||
| rustc_index | ||
| rustc_infer | ||
| rustc_interface | ||
| rustc_lexer | ||
| rustc_lint | ||
| rustc_lint_defs | ||
| rustc_llvm | ||
| rustc_log | ||
| rustc_macros | ||
| rustc_metadata | ||
| rustc_middle | ||
| rustc_mir_build | ||
| rustc_mir_dataflow | ||
| rustc_mir_transform | ||
| rustc_monomorphize | ||
| rustc_parse | ||
| rustc_parse_format | ||
| rustc_passes | ||
| rustc_plugin_impl | ||
| rustc_privacy | ||
| rustc_query_impl | ||
| rustc_query_system | ||
| rustc_resolve | ||
| rustc_serialize | ||
| rustc_session | ||
| rustc_smir | ||
| rustc_span | ||
| rustc_symbol_mangling | ||
| rustc_target | ||
| rustc_trait_selection | ||
| rustc_traits | ||
| rustc_transmute | ||
| rustc_ty_utils | ||
| rustc_type_ir | ||