https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #22 from PeteVine ---
> I don't know what exactly "fixed" this
That would be nice to know. This I can say for sure: gcc 7.2.1 20171116 still
produces slower profiled code on the target system.
I've also discovered, compiling and
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
Ramana Radhakrishnan changed:
What|Removed |Added
Target Milestone|--- |8.0
--- Comment #21 from Ramana
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
PeteVine changed:
What|Removed |Added
Status|WAITING |RESOLVED
Resolution|---
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #19 from PeteVine ---
Created attachment 42694
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42694=edit
Better assembly after profiling
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #18 from PeteVine ---
> Well that sounds like the same issue.
> Note -fprofile-generate simple inserts counters in the generated code. In
> fact the generated code is practically identical between Cortex-A5 and
> Cortex-A7.
As
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #17 from wilco at gcc dot gnu.org ---
(In reply to PeteVine from comment #16)
> Also, I'd like to repeat the fact using -mcpu=cortex-a7 fixes the issue (no
> library calls present).
Cortex-A7 has hardware division so it doesn't emit
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #16 from PeteVine ---
Also, I'd like to repeat the fact using -mcpu=cortex-a7 fixes the issue (no
library calls present).
Incidentally, having run that A7 profiled binary on a Cortex-A53, I'm seeing a
10% hit compared to a vanilla
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #15 from PeteVine ---
I don't have a cross-compiler built/installed.
If you're positive the bug doesn't reproduce on your end (targeting generic or
A5 codegen), then maybe it's about some interaction between gcc instrumentation
and
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #14 from wilco at gcc dot gnu.org ---
(In reply to PeteVine from comment #11)
> I've just retested gcc7 on both ARM platforms.
>
> AArch64 gets a 3% improvement now, while ARMv7 reproduces the issue, just as
> before. I'm
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #13 from PeteVine ---
Created attachment 41240
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41240=edit
Assembly files produced with -fverbose-asm
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #12 from PeteVine ---
It even reproduces the following way:
I built an instrumented ARMv7 binary natively, ran it on a Cortex-A53, copied
the gcda file back, recompiled with -fprofile-use and got the same 20%
slowdown.
Surely, that
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #11 from PeteVine ---
I've just retested gcc7 on both ARM platforms.
AArch64 gets a 3% improvement now, while ARMv7 reproduces the issue, just as
before. I'm compiling/profiling on a Cortex A5 which could be the main reason
behind
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
wilco at gcc dot gnu.org changed:
What|Removed |Added
Status|NEW |WAITING
CC|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #9 from PeteVine ---
It seems the LPATHBench exhibits the same issue.
https://raw.githubusercontent.com/logicchains/LPATHBench/master/c_fast.c
compiled the following way:
gcc -falign-functions=32 -std=gnu99 -O2 -mcpu=cortex-a5
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #8 from PeteVine ---
Created attachment 39749
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39749=edit
aarch64 assembly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
--- Comment #7 from PeteVine ---
Even though it's probably a dfifferent issue (affecting GCC6/7), profiling
makes the solver about 2-3% slower on aarch64:
profiled/non-profiled
gcc5.4 799/875
gcc6.2 790/773
gcc7.0 752/730
But guess what,
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70773
Ramana Radhakrishnan changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed|
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