https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
--- Comment #10 from James Greenhalgh ---
The most striking improvement was in libquantum, for which we saw a 15%
performance improvement on Cortex-A72 (3% on cortex-A57) directly attributable
to basic block ordering after this patch.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
--- Comment #9 from Brian Rzycki ---
Hello James,
If this is working as designed this may just be a case of having to live with
the regression. Do we know if anyone analyzed the net-benefit of Honza's patch?
If more benchmarks/tests win then I
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
--- Comment #8 from James Greenhalgh ---
In the case before Honza's patch, corrupt profile information leads to a branch
being marked as 100% taken. After Honza's patch, the branch is instead seen
with 95.6% taken:
(jump_insn 1916 1915 1922 309
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
Jeffrey A. Law changed:
What|Removed |Added
Priority|P3 |P2
CC|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
--- Comment #7 from James Greenhalgh ---
I'm not sure there are any bugs here to fix, though I can still reproduce the
performance differences.
First up, basic block reordering causes an issue across all microarchitectures
on which I've looked
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
--- Comment #6 from Brian Rzycki ---
James, my apologies if it wasn't clear enough what the compile options were.
The test platform in this case is a Juno A57 running Ubuntu.
I actually never turned off -mcpu=cortex-a57 during my testing. I'll
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
James Greenhalgh changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
--- Comment #4 from Brian Rzycki ---
Hi James, thank you for taking the time to test this. Unfortunately I can't
post the original code because of its license. The problem is with the
weighting changing enough that at least one pair of if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534
James Greenhalgh changed:
What|Removed |Added
CC||jgreenhalgh at gcc dot gnu.org
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