Resent in plain text mode .. David
On Fri, Apr 15, 2011 at 9:28 AM, Xinliang David Li <davi...@google.com> wrote: > > Honza, do you have a chance to take a look at it? > Thanks, > > David > > On Wed, Apr 13, 2011 at 3:25 PM, Xinliang David Li <davi...@google.com> wrote: >> >> Hi, in current FDO implementation, the source file version used in >> profile-generate needs to strictly match the version used in >> profile-use -- simple formating changes will invalidate the profile >> data (use of it will lead to compiler error or ICE). There are two >> main problems that lead to the weakness: >> >> 1) the function checksum is computed based on line number and number >> of basic blocks -- this means any line number change will invalidate >> the profile data. In fact, line number should play very minimal role >> in profile matching decision. Another problem is that number of basic >> blocks is also not a good indicator whether CFG matches or not. >> 2) cgraph's pid is used as the key to find the matching profile data >> for a function. If there is any new function added, or if the order of >> the functions changes, the profile data is invalidated. >> >> The attached is a patch from google that improves this. >> 1) function checksum is split into two parts: lineno checksum and cfg >> checksum >> 2) function assembler name is used in profile hashing. >> >> Bootstrapped and regression tested on x86_64/linux. >> >> Ok for trunk? >> >> Thanks, >> >> David >> >> 2011-04-13 Xinliang David Li <davi...@google.com> >> >> * tree.c (crc32_byte): New function. >> * tree.h (crc32_byte): New function. >> * gcov.c (function_info): Add new fields. >> (read_graph_file): Handle new fields. >> (read_count_file): Handle name. >> * gcov-io.c (gcov_string_length): New function. >> (gcov_write_words): Bug fix. >> (gcov_read_words): Bug fix. >> * gcov-io.h: New interfaces. >> * profile.c (get_exec_counts): New parameter. >> (compute_branch_probablilities): New parameter. >> (compute_value_histogram): New parameter. >> (branch_prob): Pass cfg_checksum. >> * coverage.c (get_const_string_type): New function. >> (hash_counts_entry_hash): Use string hash. >> (hash_counts_entry_eq): Use string compare. >> (htab_counts_entry_del): Delete name. >> (read_count_file): Add handling of cfg checksum. >> (get_coverage_counts): New parameter. >> (xstrdup_mask_random): New function. >> (coverage_compute_lineno_checksum): New function. >> (coverage_compute_cfg_checksum): New function. >> (coverage_begin_output): New parameter. >> (coverage_end_function): New parameter. >> (build_fn_info_type): Build new fields. >> (build_fn_info_value): Build new field values. >> * coverage.h: Interface changes. >> * libgcov.c (gcov_exit): Dump new fields. >> * gcov_dump.c (tag_function): Print new fields. >
