Re: toolchain/51094: repeatable file-system corruption: 7.99.2{7,8} i386/athlon gcc-5.3.0

[Jim Bernard <jbernard%mines.edu@localhost>]

The following reply was made to PR toolchain/51094; it has been noted by GNATS.

From: Jim Bernard <jbernard%mines.edu@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: toolchain-manager%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost,
        netbsd-bugs%NetBSD.org@localhost, jbernard%mines.edu@localhost
Subject: Re: toolchain/51094: repeatable file-system corruption: 7.99.2{7,8}
 i386/athlon gcc-5.3.0
Date: Thu, 28 Apr 2016 17:53:41 -0600

 On Thu, Apr 28, 2016 at 08:00:02PM +0000, matthew green wrote:
 > The following reply was made to PR toolchain/51094; it has been noted by GNATS.
 > 
 > From: matthew green <mrg%eterna.com.au@localhost>
 > To: Jim Bernard <jbernard%mines.edu@localhost>
 > Cc: toolchain-manager%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost,
 >     netbsd-bugs%NetBSD.org@localhost, gnats-bugs%NetBSD.org@localhost
 > Subject: re: toolchain/51094: repeatable file-system corruption: 7.99.2{7,8} i386/athlon gcc-5.3.0
 > Date: Fri, 29 Apr 2016 05:57:28 +1000
 > 
 >  i have commited a hack to amd64 kernel builds to use this option
 >  for ufs_lookup.c only.  if you update it should work without any
 >  special options.  (i was running a kernel with everything built
 >  -fno-tree-vrp -Wno-error=maybe-uninitialized to avoid the issues
 >  you mentioned, but they don't apply to the problem source.)
 
 I can confirm that using -fno-tree-vrp on just this file fixes the problem
 for me.  Since my cpu is a 32-bit cpu, instead of using this change to the
 amd64 Makefile, I just put it into my kernel config, passing it via
 CPUOPTS, rather than COPTS with:
 
 makeoptions	"CPUFLAGS.ufs_lookup.c"+="-fno-tree-vrp"
 
 >  ideally, someone should do something like this:
 >  
 >  remove this hack and instead apply it directly inside ufs_lookup.c
 >  itself.  there are only a relatively small number of functions so
 >  it shouldn't be too hard to binary search.  you can use (i believe)
 >  __attribute__((__optimize__("no-tree-vrp"))) on each function to
 >  turn it off just here, and then test against a known failing case.
 
 That works.  The function is ufs_direnter().  It's a fairly long one, though.
 
 -- Jim