From: Stefan Schulze Frielinghaus <stefansf@linux.ibm.com>
To: gcc@gcc.gnu.org
Subject: How to debug while using LTO?
Date: Thu, 24 Nov 2022 17:26:56 +0100 [thread overview]
Message-ID: <Y3+bUIdcU6FRbHpT@li-42a4824c-28a0-11b2-a85c-f55c0d5956ce.ibm.com> (raw)
Hi everyone,
Currently I'm looking into a wrong-code bug and would like to understand
a certain optimization done by combine during local transformation.
Without LTO I would simply debug cc1 and step through combine. However,
with LTO enabled AFAIK I have to debug lto1 instead. In order to get
the lto1 command line of interest according to
https://gcc.gnu.org/legacy-ml/gcc/2009-11/msg00047.html
I have to pass -Wl,-debug to gcc in order to get the command for
collect2 to which itself I have to pass -plugin-opt=-debug in order to
get the command for lto-wrapper. According to the aforementioned mail I
should add option -debug to lto-wrapper, however, it appears to me that
option -debug was removed. I gave options -v and -### a chance without
luck, i.e., those only print the usual environment variables and
afterwards a list of object files like
/tmp/ccPEIV35.ltrans0.ltrans.o
/tmp/ccNmpKfS.debug.temp.o
/tmp/cceiCIFg.debug.temp.o
/tmp/ccZ4Qc7E.debug.temp.o
...
but no lto1 command. Thus, how do you retrieve the lto1 command?
While desperate I retrieved it manually via strace. However, the lto1
command refers to temporary files which have been erased meanwhile. I
actually didn't expect that because I added -save-temps to all the
intermediate commands which is also reflected in the environment
variable COLLECT_GCC_OPTIONS. Thus, how do you keep temporary files?
Cheers,
Stefan
next reply other threads:[~2022-11-24 16:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-24 16:26 Stefan Schulze Frielinghaus [this message]
2022-11-24 16:53 ` Richard Biener
2022-11-30 10:49 ` Stefan Schulze Frielinghaus
2022-11-30 13:22 ` Richard Biener
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