http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #19 from Jakub Jelinek jakub at gcc dot gnu.org 2012-11-21
08:40:52 UTC ---
(In reply to comment #18)
For actual ThreadSanitizer runtime -fPIC -ftls-model=initial-exec causes
degradation of generated code. Linker emits the
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #20 from Dmitry Vyukov dvyukov at google dot com 2012-11-21
09:04:07 UTC ---
(In reply to comment #19)
(In reply to comment #18)
For actual ThreadSanitizer runtime -fPIC -ftls-model=initial-exec causes
degradation of
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #21 from Jakub Jelinek jakub at gcc dot gnu.org 2012-11-21
09:23:56 UTC ---
(In reply to comment #20)
What I see is that it also affect code generation (register allocation). Do we
need to file a bug on that?
If you see a
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #18 from Dmitry Vyukov dvyukov at google dot com 2012-11-21
07:45:20 UTC ---
(In reply to comment #17)
When building libtsan as a shared library (for which I had to hack our
assembly
blobs a bit) we get two sources of
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #14 from Jakub Jelinek jakub at gcc dot gnu.org 2012-11-19
08:54:47 UTC ---
I bet 9.5% or more of that is due to the PLT call. The thing is, even when you
have initial-exec TLS model code, if you link it into an executable and
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #15 from Konstantin Serebryany konstantin.s.serebryany at gmail
dot com 2012-11-19 09:03:35 UTC ---
You are right that -fPIC -ftls-model=initial-exec does not affect performance
if we link libtsan statically (I checked).
As
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #16 from Konstantin Serebryany konstantin.s.serebryany at gmail
dot com 2012-11-19 09:06:26 UTC ---
So, using -fPIC -ftls-model=initial-exec is a great idea, it will allow
to build the files once and have both static and
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #17 from Dmitry Vyukov dvyukov at google dot com 2012-11-19
10:53:04 UTC ---
When building libtsan as a shared library (for which I had to hack our assembly
blobs a bit) we get two sources of slowdown:
1. __tsan_read8 and
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #9 from Konstantin Serebryany konstantin.s.serebryany at gmail dot
com 2012-11-18 19:35:43 UTC ---
As dvyuokv@ pointed out,
-ftls-model=initial-exec improves the situation, but does not fully help.
Experiment:
% cat x.c
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #10 from Jakub Jelinek jakub at gcc dot gnu.org 2012-11-18
19:54:37 UTC ---
(In reply to comment #9)
NOT-SO-BAD: -fPIC -shared -ftls-model=initial-exec
% gcc x.c -O2 -fPIC -shared -o x.so -ftls-model=initial-exec ; objdump
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #11 from Konstantin Serebryany konstantin.s.serebryany at gmail
dot com 2012-11-18 19:59:42 UTC ---
The above comment is correct.
-fPIE is only applicable if we build libtsan.a and link it statically to the
pie executable.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #12 from Jakub Jelinek jakub at gcc dot gnu.org 2012-11-18
20:09:39 UTC ---
That would effectively require building libtsan as libtsan.so.0, libtsan.a
(both -fPIC built) and libtsan_pie.a (-fPIE built), where the gcc driver
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #13 from Konstantin Serebryany konstantin.s.serebryany at gmail
dot com 2012-11-19 04:13:23 UTC ---
of course everything would need to be done only given appropriate benchmarks
of real-world programs.
We have a synthetic
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #7 from H.J. Lu hjl.tools at gmail dot com 2012-11-17 20:35:57
UTC ---
(In reply to comment #6)
Answering my own question: we can get static linking with
-Wl,-Bstatic -lasan -Wl,-Bdynamic -ldl -lpthread
The
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
Markus Trippelsdorf markus at trippelsdorf dot de changed:
What|Removed |Added
CC|
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
Andrew Pinski pinskia at gcc dot gnu.org changed:
What|Removed |Added
Version|unknown |4.8.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #2 from Dmitry Vyukov dvyukov at google dot com 2012-11-16
17:20:43 UTC ---
Not much better performance.
Sole -fPIE vs -fPIC gives us 20% speedup on real programs. Indirect call will
add another 10%.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
Jakub Jelinek jakub at gcc dot gnu.org changed:
What|Removed |Added
Status|UNCONFIRMED |RESOLVED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #4 from Konstantin Serebryany konstantin.s.serebryany at gmail dot
com 2012-11-16 20:28:34 UTC ---
You have been warned (especially about tsan performance. tsan run-time heavily
depends on TLS, and TLS is much slower with -fPIC
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #5 from Jakub Jelinek jakub at gcc dot gnu.org 2012-11-16
20:46:35 UTC ---
For TLS, you can just use -ftls-model=initial-exec or __attribute__((tls_model
(initial-exec))). libasan from what I can see doesn't use TLS at all, and
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55354
--- Comment #6 from Konstantin Serebryany konstantin.s.serebryany at gmail dot
com 2012-11-16 20:54:40 UTC ---
Answering my own question: we can get static linking with
-Wl,-Bstatic -lasan -Wl,-Bdynamic -ldl -lpthread
For TLS, you
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