http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51902
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-01-19 18:04:54 UTC --- Created attachment 26385 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26385 gcc47-pr51902.patch Partial patch. The following example shows it even better, there are 5 identical 3 item ranges: static int k; static int foo (int i) { int q1 = i, q2 = i; { int q3 = i; { int q4 = i, q5 = i; { int j = i + 42; return k + (j > 14 ? j : i); } } } } int main (int argc, char **argv) { int c = argc; k = 2 * c; c = foo (c); return c; } IMHO it is impossible to handle this solely in dwarf2out.c, you don't know if the begin/end notes for a block are adjacent to its BLOCK_SUPERCONTEXT or not. The attached patch is an untested attempt to provide that info (on a per-fragment basis). If the stmt BLOCK given to add_high_low_attributes has BLOCK_SAME_RANGE bit set and all blocks in its BLOCK_FRAGMENT_CHAIN have it set as well, then you should be able to use the range of its BLOCK_SUPERCONTEXT (if both stmt and BLOCK_SUPERCONTEXT (stmt) have the same length of fragment chain, then the whole supercontext's range, otherwise some tail part of it). And recursively so. I guess in order to avoid searching through the fragment chains all the time we should clear BLOCK_SAME_RANGE if BLOCK_SAME_RANGE (BLOCK_FRAGMENT_CHAIN) is clear (somewhere still during reorder_blocks or number_blocks). And then the question is how to find the range in the .debug_ranges table effectively. Walking the whole table would be O(n^2), so have some hash table that maps the BLOCK_NUM ints that have BLOCK_SAME_RANGE children (at least one) to .debug_range offsets?
