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From: Franz Sirl <>
To: Jeff Law <>,
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: <> (raw)
In-Reply-To: <>

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 

make[3]: Entering directory 
bin/ -nostdinc++ 
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 
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/
../../gcc/ In member function 'cgraph_edge* 
../../gcc/ error: EDGE_CROSSING incorrectly set across 
same section
  1166 | }
       | ^
../../gcc/ error: No region crossing jump at section 
boundary in bb 19
during RTL pass: bbro
../../gcc/ internal compiler error: verify_flow_info failed
0xa7116e verify_flow_info()
0x1c64958 execute

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.


  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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