On Mon, Sep 14, 2020 at 09:31:52AM +0200, Richard Biener wrote: > But does it make any noticable difference in the end? Using
Yes. > bp_pack_var_len_unsigned just causes us to [u]leb encode half-bytes > rather than full bytes. Using hardcoded 8/16/32/64 makes it still > dependent on what 'int' is at maximum on the host. > > That is, I'd indeed prefer bp_pack_var_len_unsigned over hard-coding > 8, 16, etc., but can you share a size comparison of the bitpack? > I guess with bp_pack_var_len_unsigned it might shrink in half > compared to the current code and streaming standard -O2? So, I've tried --- gcc/tree-streamer-out.c.jj 2020-07-28 15:39:10.079755251 +0200 +++ gcc/tree-streamer-out.c 2020-09-14 10:31:29.106957258 +0200 @@ -489,7 +489,11 @@ streamer_write_tree_bitfields (struct ou pack_ts_translation_unit_decl_value_fields (ob, &bp, expr); if (CODE_CONTAINS_STRUCT (code, TS_OPTIMIZATION)) +{ +long ts = ob->main_stream->total_size; cl_optimization_stream_out (ob, &bp, TREE_OPTIMIZATION (expr)); +fprintf (stderr, "total_size %ld\n", (long) (ob->main_stream->total_size - ts)); +} if (CODE_CONTAINS_STRUCT (code, TS_CONSTRUCTOR)) bp_pack_var_len_unsigned (&bp, CONSTRUCTOR_NELTS (expr)); hack without and with the following patch on a simple small testcase with -O2 -flto. Got 574 bytes without the opc-save-gen.awk change and 454 bytes with it, that is ~ 21% saving on the TREE_OPTIMIZATION streaming. 2020-09-14 Jakub Jelinek <ja...@redhat.com> * optc-save-gen.awk: In cl_optimization_stream_out use bp_pack_var_len_{int,unsigned} instead of bp_pack_value. In cl_optimization_stream_in use bp_unpack_var_len_{int,unsigned} instead of bp_unpack_value. Formatting fix. --- gcc/optc-save-gen.awk.jj 2020-09-14 09:04:35.879854156 +0200 +++ gcc/optc-save-gen.awk 2020-09-14 10:38:47.722424942 +0200 @@ -1257,8 +1257,10 @@ for (i = 0; i < n_opt_val; i++) { otype = var_opt_val_type[i]; if (otype ~ "^const char \\**$") print " bp_pack_string (ob, bp, ptr->" name", true);"; + else if (otype ~ "^unsigned") + print " bp_pack_var_len_unsigned (bp, ptr->" name");"; else - print " bp_pack_value (bp, ptr->" name", 64);"; + print " bp_pack_var_len_int (bp, ptr->" name");"; } print " for (size_t i = 0; i < sizeof (ptr->explicit_mask) / sizeof (ptr->explicit_mask[0]); i++)"; print " bp_pack_value (bp, ptr->explicit_mask[i], 64);"; @@ -1274,14 +1276,15 @@ print "{"; for (i = 0; i < n_opt_val; i++) { name = var_opt_val[i] otype = var_opt_val_type[i]; - if (otype ~ "^const char \\**$") - { - print " ptr->" name" = bp_unpack_string (data_in, bp);"; - print " if (ptr->" name")"; - print " ptr->" name" = xstrdup (ptr->" name");"; + if (otype ~ "^const char \\**$") { + print " ptr->" name" = bp_unpack_string (data_in, bp);"; + print " if (ptr->" name")"; + print " ptr->" name" = xstrdup (ptr->" name");"; } + else if (otype ~ "^unsigned") + print " ptr->" name" = (" var_opt_val_type[i] ") bp_unpack_var_len_unsigned (bp);"; else - print " ptr->" name" = (" var_opt_val_type[i] ") bp_unpack_value (bp, 64);"; + print " ptr->" name" = (" var_opt_val_type[i] ") bp_unpack_var_len_int (bp);"; } print " for (size_t i = 0; i < sizeof (ptr->explicit_mask) / sizeof (ptr->explicit_mask[0]); i++)"; print " ptr->explicit_mask[i] = bp_unpack_value (bp, 64);"; Jakub