This patch addresses PR bootstrap/63432 which was an insanity in the
probabilities created during jump threading. This was caused by threading
multiple times along the same path leading to the second jump thread path being
corrupted, which in turn caused the profile update code to fail. There
was code in mark_threaded_blocks that intended to catch and suppress
these cases of threading multiple times along the same path, but it
was sensitive to the order in which the paths were discovered and recorded.
This patch changes the detection to do two passes and removes the ordering
sensitivity.
Also, while fixing this I realized that the previous method of checking
the entry BB's profile count was not an accurate way to determine whether
the function has any non-zero profile counts. Created a new routine
to walk the path and see if it has all zero profile counts and estimated
frequencies.
Bootstrapped and tested on x86_64-unknown-linux-gnu. Also did an LTO
profiledbootstrap.
Ok for trunk?
Thanks,
Teresa
2014-10-07 Teresa Johnson <tejohnson@google.com>
PR bootstrap/63432.
* tree-ssa-threadupdate.c (estimated_freqs_path): New function.
(ssa_fix_duplicate_block_edges): Invoke it.
(mark_threaded_blocks): Make two passes to avoid ordering dependences.