From: Franz Sirl <Franz.Sirl-kernel@lauterbach.com>
To: Jeff Law <jlaw@ventanamicro.com>, gcc-patches@gcc.gnu.org
Subject: Re: [RFA] Minor improvement to coremark, avoid unconditional jump to return
Date: Fri, 7 Oct 2022 12:51:16 +0200 [thread overview]
Message-ID: <ef770c95-8e94-cb7d-af9e-e04c4b199bb5@lauterbach.com> (raw)
In-Reply-To: <ada747e8-6ba5-70f9-f7a8-eb1685b3b09b@ventanamicro.com>
Am 2022-09-25 um 18:28 schrieb Jeff Law:
> This is a minor improvement for the core_list_find routine in coremark.
>
>
> Basically for riscv, and likely other targets, we can end up with an
> unconditional jump to a return statement. This is a result of
> compensation code created by bb-reorder, and no jump optimization pass
> runs after bb-reorder to clean this stuff up.
>
> This patch utilizes preexisting code to identify suitable branch targets
> as well as preexisting code to emit a suitable return, so it's pretty
> simple. Note that when we arrange to do this optimization, the original
> return block may become unreachable. So we conditionally call
> delete_unreachable_blocks to fix that up.
>
> This triggers ~160 times during an x86_64 bootstrap. Naturally it
> bootstraps and regression tests on x86_64.
>
> I've also bootstrapped this on riscv64, regression testing with qemu
> shows some regressions, but AFAICT they're actually qemu bugs with
> signal handling/delivery -- qemu user mode emulation is not consistently
> calling user defined signal handlers. Given the same binary, sometimes
> they'll get called and the test passes, other times the handler isn't
> called and the test (of course) fails. I'll probably spend some time to
> try and chase this down for the sake of making testing easier.
>
>
> OK for the trunk?
Hello Jeff,
I've bisected this change to break a "profiledbootstrap" on x86_64 like
that:
make[3]: Entering directory
'/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/gcc'
/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/./prev-gcc/xg++
-B/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/./prev-gcc/
-B/usr/x86_64-suse-linux/
bin/ -nostdinc++
-B/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/prev-x86_64-suse-linux/libstdc++-v3/src/.libs
-B/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64
-suse-linux/prev-x86_64-suse-linux/libstdc++-v3/libsupc++/.libs
-I/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/prev-x86_64-suse-linux/libstdc++-v3/include/x86_64-suse-linu
x
-I/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/prev-x86_64-suse-linux/libstdc++-v3/include
-I/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/libstdc++-v3/libsupc++
-L
/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/prev-x86_64-suse-linux/libstdc++-v3/src/.libs
-L/home/fsirl/rpmbuild/BUILD/gcc-13.0.0+gitr13+2871/obj-x86_64-suse-linux/prev-x8
6_64-suse-linux/libstdc++-v3/libsupc++/.libs -fno-PIE -c -O2 -g
-fmessage-length=0 -D_FORTIFY_SOURCE=2 -funwind-tables
-fasynchronous-unwind-tables -U_FORTIFY_SOURCE -fprofile-use
-fprofile-reprod
ucible=parallel-runs -DIN_GCC -fno-exceptions -fno-rtti
-fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
-Wcast-qual -Wmissing-format-attribute -Woverloaded-virtual -pedantic
-Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -fno-common
-DHAVE_CONFIG_H -I. -I. -I../../gcc -I../../gcc/. -I../../gcc/../include
-I../../gcc/../libcpp/include -I../../gcc/../libcody
-I../../gcc/../libdecnumber -I../../gcc/../libdecnumber/bid
-I../libdecnumber -I../../gcc/../libbacktrace -o cgraph.o -MT cgraph.o
-MMD -MP -MF ./.deps/cgraph.TPo ../../gcc/cgraph.cc
../../gcc/cgraph.cc: In member function 'cgraph_edge*
cgraph_edge::first_speculative_call_target()':
../../gcc/cgraph.cc:1166:1: error: EDGE_CROSSING incorrectly set across
same section
1166 | }
| ^
../../gcc/cgraph.cc:1166:1: error: No region crossing jump at section
boundary in bb 19
during RTL pass: bbro
../../gcc/cgraph.cc:1166:1: internal compiler error: verify_flow_info failed
0xa7116e verify_flow_info()
../../gcc/cfghooks.cc:284
0x1c64958 execute
../../gcc/bb-reorder.cc:2663
In such a case, what do you need to reproduce it? I'm a mere user of the
Suse RPM builds here, no idea if profiling needs any extra data to
reproduce to bug.
Franz.
next prev parent reply other threads:[~2022-10-07 10:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-25 16:28 Jeff Law
2022-09-26 7:53 ` Richard Biener
2022-10-07 10:51 ` Franz Sirl [this message]
2022-10-07 11:33 ` Richard Biener
2022-10-07 14:13 ` Jeff Law
2022-10-07 15:11 ` Franz Sirl
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