[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #17 from Michael Meissner  ---
Author: meissner
Date: Tue Aug 29 21:06:21 2017
New Revision: 251437

URL: https://gcc.gnu.org/viewcvs?rev=251437=gcc=rev
Log:


[gcc]
2017-07-13  Michael Meissner  

Back port from trunk
2017-07-12  Michael Meissner  

PR target/81193
* config/rs6000/rs6000-c.c (rs6000_cpu_cpp_builtins): If GLIBC
provides the hardware capability bits, define the macro
__BUILTIN_CPU_SUPPORTS__.
* config/rs6000/rs6000.c (cpu_expand_builtin): Generate a warning
if GLIBC does not provide the hardware capability bits.  Add a
gcc_unreachable call if the built-in cpu function is neither
__builtin_cpu_is nor __builtin_cpu_supports.
* doc/extend.texi (PowerPC built-in functions): Document that
GLIBC 2.23 or newer is needed by __builtin_cpu_is and
__builtin_cpu_supports.  Document the macros defined by GCC if the
newer GLIBC is available.

[gcc/testsuite]
2017-07-13  Michael Meissner  

Back port from trunk
2017-06-28  Michael Meissner  

PR target/81193
* lib/target-supports.exp
(check_ppc_cpu_supports_hw_available): New test to make sure
__builtin_cpu_supports works on power7 and newer.

Back port from trunk
2017-07-12  Michael Meissner  

PR target/81193
* gcc.target/powerpc/cpu-builtin-1.c: Add guard against using
__builtin_cpu_supports with old GLIBC's.


Modified:
branches/gcc-6-branch/gcc/ChangeLog
branches/gcc-6-branch/gcc/testsuite/ChangeLog

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

Michael Meissner  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |FIXED

--- Comment #16 from Michael Meissner  ---
Fixed in trunk, and backported to GCC 7/6.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #15 from Michael Meissner  ---
Author: meissner
Date: Wed Jul 19 22:05:20 2017
New Revision: 250371

URL: https://gcc.gnu.org/viewcvs?rev=250371=gcc=rev
Log:
[gcc]
2017-07-19  Michael Meissner  

Back port from trunk
2017-07-12  Michael Meissner  

PR target/81193
* config/rs6000/rs6000-c.c (rs6000_cpu_cpp_builtins): If GLIBC
provides the hardware capability bits, define the macro
__BUILTIN_CPU_SUPPORTS__.
* config/rs6000/rs6000.c (cpu_expand_builtin): Generate a warning
if GLIBC does not provide the hardware capability bits.  Add a
gcc_unreachable call if the built-in cpu function is neither
__builtin_cpu_is nor __builtin_cpu_supports.
* doc/extend.texi (PowerPC built-in functions): Document that
GLIBC 2.23 or newer is needed by __builtin_cpu_is and
__builtin_cpu_supports.  Document the macros defined by GCC if the
newer GLIBC is available.

[gcc/testsuite]
2017-07-19  Michael Meissner  

Back port from trunk
2017-07-12  Michael Meissner  

PR target/81193
* gcc.target/powerpc/cpu-builtin-1.c: Change test to use #ifdef
__BUILTIN_CPU_SUPPORTS to see if the GLIBC is new enough that
__builtin_cpu_is and __builtin_cpu_supports are supported.


Modified:
branches/gcc-6-branch/gcc/config/rs6000/rs6000-c.c
branches/gcc-6-branch/gcc/config/rs6000/rs6000.c
branches/gcc-6-branch/gcc/doc/extend.texi
branches/gcc-6-branch/gcc/testsuite/gcc.target/powerpc/cpu-builtin-1.c

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #14 from Michael Meissner  ---
Author: meissner
Date: Wed Jul 19 20:31:53 2017
New Revision: 250368

URL: https://gcc.gnu.org/viewcvs?rev=250368=gcc=rev
Log:
[gcc]
2017-07-19  Michael Meissner  

Back port from trunk
2017-07-12  Michael Meissner  

PR target/81193
* config/rs6000/rs6000-c.c (rs6000_cpu_cpp_builtins): If GLIBC
provides the hardware capability bits, define the macro
__BUILTIN_CPU_SUPPORTS__.
* config/rs6000/rs6000.c (cpu_expand_builtin): Generate a warning
if GLIBC does not provide the hardware capability bits.  Add a
gcc_unreachable call if the built-in cpu function is neither
__builtin_cpu_is nor __builtin_cpu_supports.
* doc/extend.texi (PowerPC built-in functions): Document that
GLIBC 2.23 or newer is needed by __builtin_cpu_is and
__builtin_cpu_supports.  Document the macros defined by GCC if the
newer GLIBC is available.

[gcc/testsuite]
2017-07-19  Michael Meissner  

Back port from trunk
2017-07-12  Michael Meissner  

PR target/81193
* gcc.target/powerpc/cpu-builtin-1.c: Change test to use #ifdef
__BUILTIN_CPU_SUPPORTS to see if the GLIBC is new enough that
__builtin_cpu_is and __builtin_cpu_supports are supported.


Modified:
branches/gcc-7-branch/gcc/ChangeLog
branches/gcc-7-branch/gcc/config/rs6000/rs6000-c.c
branches/gcc-7-branch/gcc/config/rs6000/rs6000.c
branches/gcc-7-branch/gcc/doc/extend.texi
branches/gcc-7-branch/gcc/testsuite/ChangeLog
branches/gcc-7-branch/gcc/testsuite/gcc.target/powerpc/cpu-builtin-1.c

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #13 from Michael Meissner  ---
Author: meissner
Date: Wed Jul 12 23:07:50 2017
New Revision: 250165

URL: https://gcc.gnu.org/viewcvs?rev=250165=gcc=rev
Log:
[gcc]
2017-07-12  Michael Meissner  

PR target/81193
* config/rs6000/rs6000-c.c (rs6000_cpu_cpp_builtins): If GLIBC
provides the hardware capability bits, define the macro
__BUILTIN_CPU_SUPPORTS__.
* config/rs6000/rs6000.c (cpu_expand_builtin): Generate a warning
if GLIBC does not provide the hardware capability bits.  Add a
gcc_unreachable call if the built-in cpu function is neither
__builtin_cpu_is nor __builtin_cpu_supports.
(rs6000_get_function_versions_dispatcher): Change the warning
that an old GLIBC is used which does not export the capability
bits to be an error.
* doc/extend.texi (target_clones attribute): Document the
restriction that GLIBC 2.23 or newer is needed on the PowerPC.
(PowerPC built-in functions): Document that GLIBC 2.23 or newer is
needed by __builtin_cpu_is and __builtin_cpu_supports.  Document
the macros defined by GCC if the newer GLIBC is available.

[gcc/testsuite]
2017-07-12  Michael Meissner  

PR target/81193
* gcc.target/powerpc/bmi-andn-1.c: Add guard against using
__builtin_cpu_supports with old GLIBC's.
* gcc.target/powerpc/bmi-andn-2.c: Likewise.
* gcc.target/powerpc/bmi-bextr-1.c: Likewise.
* gcc.target/powerpc/bmi-bextr-2.c: Likewise.
* gcc.target/powerpc/bmi-bextr-4.c: Likewise.
* gcc.target/powerpc/bmi-bextr-5.c: Likewise.
* gcc.target/powerpc/bmi-blsi-1.c: Likewise.
* gcc.target/powerpc/bmi-blsi-2.c: Likewise.
* gcc.target/powerpc/bmi-blsmsk-1.c: Likewise.
* gcc.target/powerpc/bmi-blsmsk-2.c: Likewise.
* gcc.target/powerpc/bmi-blsr-1.c: Likewise.
* gcc.target/powerpc/bmi-blsr-2.c: Likewise.
* gcc.target/powerpc/bmi-tzcnt-1.c: Likewise.
* gcc.target/powerpc/bmi-tzcnt-2.c: Likewise.
* gcc.target/powerpc/bmi2-bzhi32-1.c: Likewise.
* gcc.target/powerpc/bmi2-bzhi64-1.c: Likewise.
* gcc.target/powerpc/bmi2-mulx32-1.c: Likewise.
* gcc.target/powerpc/bmi2-mulx32-2.c: Likewise.
* gcc.target/powerpc/bmi2-mulx64-1.c: Likewise.
* gcc.target/powerpc/bmi2-mulx64-2.c: Likewise.
* gcc.target/powerpc/bmi2-pdep32-1.c: Likewise.
* gcc.target/powerpc/bmi2-pdep64-1.c: Likewise.
* gcc.target/powerpc/bmi2-pext32-1.c: Likewise.
* gcc.target/powerpc/bmi2-pext64-1.c: Likewise.
* gcc.target/powerpc/cpu-builtin-1.c: Likewise.

[libgcc]
2017-07-12  Michael Meissner  

PR target/81193
* configure.ac (PowerPC float128 hardware support): Test whether
we can use __builtin_cpu_supports before enabling the ifunc
handler.
* configure: Regenerate.


Modified:
trunk/gcc/ChangeLog
trunk/gcc/config/rs6000/rs6000-c.c
trunk/gcc/config/rs6000/rs6000.c
trunk/gcc/doc/extend.texi
trunk/gcc/testsuite/ChangeLog
trunk/gcc/testsuite/gcc.target/powerpc/bmi-andn-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-andn-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-bextr-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-bextr-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-bextr-4.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-bextr-5.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-blsi-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-blsi-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-blsmsk-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-blsmsk-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-blsr-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-blsr-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-tzcnt-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi-tzcnt-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-bzhi32-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-bzhi64-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-mulx32-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-mulx32-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-mulx64-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-mulx64-2.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-pdep32-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-pdep64-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-pext32-1.c
trunk/gcc/testsuite/gcc.target/powerpc/bmi2-pext64-1.c
trunk/gcc/testsuite/gcc.target/powerpc/cpu-builtin-1.c
trunk/libgcc/ChangeLog
trunk/libgcc/configure
trunk/libgcc/configure.ac

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #12 from Michael Meissner  ---
Created attachment 41721
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41721=edit
Proposed patch to fix the problem

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #11 from Michael Meissner  ---
Author: meissner
Date: Wed Jun 28 13:07:12 2017
New Revision: 249737

URL: https://gcc.gnu.org/viewcvs?rev=249737=gcc=rev
Log:
[gcc]
2017-06-28  Michael Meissner  

PR ipa/81238
* multiple_target.c (create_dispatcher_calls): Set the default
clone to be static, not public.

[gcc/testsuite]
2017-06-28  Michael Meissner  

PR target/81193
* lib/target-supports.exp
(check_ppc_cpu_supports_hw_available): New test to make sure
__builtin_cpu_supports works on power7 and newer.


Modified:
trunk/gcc/ChangeLog
trunk/gcc/multiple_target.c
trunk/gcc/testsuite/ChangeLog
trunk/gcc/testsuite/lib/target-supports.exp

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #10 from Michael Meissner  ---
Created attachment 41642
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41642=edit
Patch to add ppc_cpu_supports_hw target support for tests

BTW, the patch attached allows us to check whether __builtin_cpu_supports works
on power7 and newer systems.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #9 from Michael Meissner  ---
Well in theory we could add yet another switch to enable/disable the warning,
but we have too many switches as it is.

Note, I've put a warning in my development version of the target_clones
patches, and I think I will keep it (my warning is only if you try to use
target_clones on an old system).

We probably should update the gcc documentation to mention this restriction.

Most users won't be able to use __builtin_cpu_ until their distro updates
to a new glibc (i.e. years).  The Advance Toolchain users will be to use it.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[bergner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #8 from Peter Bergner  ---
(In reply to Michael Meissner from comment #4)
> I think for the problem of using __builtin_cpu_, we should issue a 
> warning
> (not a fatal error) if the configured GLIBC is too old saying you need to link
> against a newer library, but generate the same code that we normally do.  
> Given
> there is a reference to an external provided with the new glibc, it should be
> safe, because you would get a linker error if you actually tried to use it 
> with
> an old library.  It would allow creation of libraries with functions using
> __builtin_cpu_* and target_clone with an old compiler, providing the library 
> is
> linked appropriately.

But with your patch and one being contemplated for float128-ifunc.c in libgcc,
GCC will be a user of those builtins, so if we build on a system with an old
GLIBC, we'll get a bootstrap / build failure.  We can't have that.

I'm also starting to wonder about the warning.  We cannot just always emit the
warning, because the GCC bootstrap uses -Werror, so again, we'd end up with a
bootstrap / build error.  I agree that it would be nice to tell normal users
that the builtin they're using to always going to return false, but how can we
turn it off for GCC builds?

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[tuliom at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

Tulio Magno Quites Machado Filho  changed:

   What|Removed |Added

 CC||tuliom at linux dot 
vnet.ibm.com

--- Comment #7 from Tulio Magno Quites Machado Filho  ---
(In reply to Michael Meissner from comment #4)
> I have no problems with restricting use of __builtin_cpu_ and
> target_clone to GLIBC 2.19 or newer (or whatever the release version is).

That's glibc 2.23.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #6 from Alan Modra  ---
> Alternatively, we would need to do two passes.  On the first pass resolve all
> of the normal functions and data locations, setting the location of ifunc
> functions in the TOC to be an error function.  The second pass would resolve
> the ifunc functions.  If an ifunc function calls another ifunc function that
> hasn't been resolved yet, it would go to the error function.

Don't hold your breath waiting for this solution.  It was proposed first here:
https://gcc.gnu.org/ml/gcc-patches/2009-07/msg01307.html

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[bergner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #5 from Peter Bergner  ---
Given Alan's comments, I think the best thing to do here is to just emit a
warning when using those builtins when the compiler was configured to use an
old glibc.  

If someone disagrees, let me know now, as I'm going to start coding up the
change to add the warning.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

Michael Meissner  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-06-26
 Ever confirmed|0   |1

--- Comment #4 from Michael Meissner  ---
I have no problems with restricting use of __builtin_cpu_ and target_clone
to GLIBC 2.19 or newer (or whatever the release version is).  Now that I think
of it, yeah, we don't want to run ifunc resolvers if it has relocations.  I
don't know whether the linker should warn about problematic code (it probably
should, or at least we need to document it somewhere).  I was just surprised
that the compiler silently sets the test to 0.

Alternatively, we would need to do two passes.  On the first pass resolve all
of the normal functions and data locations, setting the location of ifunc
functions in the TOC to be an error function.  The second pass would resolve
the ifunc functions.  If an ifunc function calls another ifunc function that
hasn't been resolved yet, it would go to the error function.

I think for the problem of using __builtin_cpu_, we should issue a warning
(not a fatal error) if the configured GLIBC is too old saying you need to link
against a newer library, but generate the same code that we normally do.  Given
there is a reference to an external provided with the new glibc, it should be
safe, because you would get a linker error if you actually tried to use it with
an old library.  It would allow creation of libraries with functions using
__builtin_cpu_* and target_clone with an old compiler, providing the library is
linked appropriately.

It would also allow the tests for target_clone to work.  Though I probably will
switch my builds to use --with-advance-toolchain to always get the new library
(now that works with bootstrap).

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

Alan Modra  changed:

   What|Removed |Added

 CC||amodra at gmail dot com

--- Comment #3 from Alan Modra  ---
Relocation problems with ifunc resolvers come about due to the fact that ifunc
resolvers run at the same time other relocations are being processed.

So..
1) If the resolver runs before its code/data has been relocated, the resolver
won't run correctly.
2) If the object requires text relocations then the text segment will be set
read/write, but this makes it non-exec so any attempt to run an ifunc resolver
will result in a segfault.

(1) is fixed for leaf function resolvers called from within the same object
(shared lib or executable), as the linker sorts ifunc relocs last.  You will
need to know the order in which an executable and its shared libraries are
relocated by ld.so if you want to call a non-local resolver, or when the
resolver itself makes non-local calls to functions that need their code/data
relocating.  Generally, don't do that.  By inspection, getauxval loads values
from the TOC/GOT, so it does need relocating, but if ld.so always relocates
libc.so first then you might be OK calling getauxval..  I don't know enough
about ld.so to answer that detail.  And, oh yeah, provided the user doesn't
override libc.so getauxval with their own version.
(2) will give you an error/warning at link time.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

--- Comment #2 from Michael Meissner  ---
One other possibility is to just remove the code that checks
TARGET_LIBC_PROVIDES_HWCAP_IN_TCB, given that when we use it there is a
reference to __parse_hwcap_and_convert_at_platform in the code.  That won't be
satisified unless you have a new enough glibc.

Though it may be friendlier to warn the user if GCC wasn't configured to use
the newer glibc.

[Bug target/81193] PowerPC GCC __builtin_cpu_is and __builtin_cpu_supports should warn about old libraries

[bergner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193

Peter Bergner  changed:

   What|Removed |Added

 CC||amodra at gcc dot gnu.org

--- Comment #1 from Peter Bergner  ---
I think 1) is doable, but I think there might be a problem with 2).  I seem to
recall Alan mentioning that we have to be careful generating relocations in
ifunc resolver functions and calling getauxval() would definitely generate one.
 Alan, can you comment on what the issue is and whether it would be safe to
call getauxval() in an ifunc resolver?