Hi! As discussed yesterday: On the streamer out side, we call clear_line_info in multiple spots which resets the current_* values to something, but on the reader side, we don't have corresponding resets in the same location, just have the stream_* static variables that keep the current values through the entire stream in (so across all the clear_line_info spots in a single LTO object but also across jumping from one LTO object to another one). Now, in an earlier version of my patch it actually broke LTO bootstrap (and a lot of LTO testcases), so for the BLOCK case I've solved it by clear_line_info setting current_block to something that should never appear, which means that in the LTO stream after the clear_line_info spots including the start of the LTO stream we force the block change bit to be set and thus BLOCK to be streamed and therefore stream_block from earlier to be ignored. But for the rest I think that is not the case, so I wonder if we don't sometimes end up with wrong line/column info because of that, or please tell me what prevents that. clear_line_info does: ob->current_file = NULL; ob->current_line = 0; ob->current_col = 0; ob->current_sysp = false; while I think NULL current_file is something that should likely be different from expanded_location (...).file (UNKNOWN_LOCATION/BUILTINS_LOCATION are handled separately and not go through the caching), I think line number 0 can sometimes occur and especially column 0 occurs frequently if we ran out of location_t with columns info. But then we do: bp_pack_value (bp, ob->current_file != xloc.file, 1); bp_pack_value (bp, ob->current_line != xloc.line, 1); bp_pack_value (bp, ob->current_col != xloc.column, 1); and stream the details only if the != is true. If that happens immediately after clear_line_info and e.g. xloc.column is 0, we would stream 0 bit and not stream the actual value, so on read-in it would reuse whatever stream_col etc. were before. Shouldn't we set some ob->current_* new bit that would signal we are immediately past clear_line_info which would force all these != checks to non-zero? Either by oring something into those tests, or perhaps: if (ob->current_reset) { if (xloc.file == NULL) ob->current_file = ""; if (xloc.line == 0) ob->current_line = 1; if (xloc.column == 0) ob->current_column = 1; ob->current_reset = false; } before doing those bp_pack_value calls with a comment, effectively forcing all 6 != comparisons to be true?
Bootstrapped/regtested on x86_64-linux and i686-linux and lto bootstrapped on x86_64-linux, ok for trunk? 2020-09-03 Jakub Jelinek <ja...@redhat.com> * lto-streamer.h (struct output_block): Add reset_locus member. * lto-streamer-out.c (clear_line_info): Set reset_locus to true. (lto_output_location_1): If reset_locus, clear it and ensure current_{file,line,col} is different from xloc members. --- gcc/lto-streamer.h.jj 2020-09-03 12:50:54.990753979 +0200 +++ gcc/lto-streamer.h 2020-09-03 17:11:51.406571519 +0200 @@ -717,6 +717,7 @@ struct output_block int current_line; int current_col; bool current_sysp; + bool reset_locus; tree current_block; /* Cache of nodes written in this section. */ --- gcc/lto-streamer-out.c.jj 2020-09-03 12:50:54.992753950 +0200 +++ gcc/lto-streamer-out.c 2020-09-03 17:16:44.601311584 +0200 @@ -60,6 +60,7 @@ clear_line_info (struct output_block *ob ob->current_line = 0; ob->current_col = 0; ob->current_sysp = false; + ob->reset_locus = true; /* Initialize to something that will never appear as block, so that the first location with block in a function etc. always streams a change_block bit and the first block. */ @@ -195,6 +196,17 @@ lto_output_location_1 (struct output_blo { expanded_location xloc = expand_location (loc); + if (ob->reset_locus) + { + if (xloc.file == NULL) + ob->current_file = ""; + if (xloc.line == 0) + ob->current_line = 1; + if (xloc.column == 0) + ob->current_col = 1; + ob->reset_locus = false; + } + bp_pack_value (bp, ob->current_file != xloc.file, 1); bp_pack_value (bp, ob->current_line != xloc.line, 1); bp_pack_value (bp, ob->current_col != xloc.column, 1); Jakub