[Bug c/64554] New: _mm_clmulepi64_si128 doesn't compile with -O2

[Bug c/64554] New: _mm_clmulepi64_si128 doesn't compile with -O2

[charles at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

            Bug ID: 64554
           Summary: _mm_clmulepi64_si128 doesn't compile with -O2
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: charles at kde dot org

The following trivial program:

#include <wmmintrin.h>

int main()
{
        __m128i a, b;
        _mm_clmulepi64_si128(a, b, 1);
}

Produces the following error at compile time:

In file included from test.c:1:0:
test.c: In function ‘main’:
/usr/lib/gcc/x86_64-linux-gnu/4.9/include/wmmintrin.h:116:1: error: inlining
failed in call to always_inline ‘_mm_clmulepi64_si128’: target specific option
mismatch
 _mm_clmulepi64_si128 (__m128i __X, __m128i __Y, const int __I)
 ^
test.c:6:2: error: called from here
  _mm_clmulepi64_si128(a, b, 1);
  ^

When compiled with the option -O2 or -O1. Compiling succeeds with -O0.



Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.9.1-19'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.1 (Debian 4.9.1-19) 

(Debian testing)
>From gcc-bugs-return-472668-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Fri Jan 09 21:35:51 2015
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From: "charles at kde dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/64554] _mm_clmulepi64_si128 doesn't compile with -O2
Date: Fri, 09 Jan 2015 21:35:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd554

--- Comment #1 from charles at kde dot org ---
It does compile with -march=westmere or later. I guess this is intended
behavior.

[Bug target/64554] _mm_clmulepi64_si128 doesn't compile with -O2

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-linux-gnu

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
What is the command line you are invoking to compile this source?  Do have the
correct options to enable it?  Like say -mpclmul?

[Bug target/64554] _mm_clmulepi64_si128 doesn't compile with -O2

[charles at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

--- Comment #3 from charles at kde dot org ---
with "gcc test.c -O2" it fails
with "gcc test.c -O2 -mpclmul" it succeeds.

[Bug target/64554] _mm_clmulepi64_si128 doesn't compile with -O2

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I don't see any bug in that.  You can't use intrinsics for ISAs that aren't
enabled, either from command line, or default -march selection, or through
target attribute on particular function, or function multi-versioning.

[Bug target/64554] _mm_clmulepi64_si128 doesn't compile with -O2

[charles at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

--- Comment #5 from charles at kde dot org ---
No you're right.

I could add, though, that the compiler should have said something.

Also, why did it compile just fine with -O0?

[Bug middle-end/64554] using _mm_clmulepi64_si128 doesn't error with -O0

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-01-12
                 CC|                            |hubicka at gcc dot gnu.org
          Component|target                      |middle-end
            Summary|_mm_clmulepi64_si128        |using _mm_clmulepi64_si128
                   |doesn't compile with -O2    |doesn't error with -O0
     Ever confirmed|0                           |1

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to charles from comment #5)
> No you're right.
> 
> I could add, though, that the compiler should have said something.
> 
> Also, why did it compile just fine with -O0?

Sounds like a bug (we should error immediately here IMHO).  Probably
needs to annotate the CIF codes with whether this is "fatal" (won't
change with other inlining, IPA or LTO).

OTOH the headers are also poorly designed to trigger this kind of error.

Maybe we want to support __attribute__((always_inline("ISA not enabled")))
instead to be able to print a custom error message?

[Bug middle-end/64554] using _mm_clmulepi64_si128 doesn't error with -O0

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64554

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #6)
> (In reply to charles from comment #5)
> > No you're right.
> > 
> > I could add, though, that the compiler should have said something.
> > 
> > Also, why did it compile just fine with -O0?
> 
> Sounds like a bug (we should error immediately here IMHO).  Probably
> needs to annotate the CIF codes with whether this is "fatal" (won't
> change with other inlining, IPA or LTO).
> 
> OTOH the headers are also poorly designed to trigger this kind of error.
> 
> Maybe we want to support __attribute__((always_inline("ISA not enabled")))
> instead to be able to print a custom error message?

The difference is that for __OPTIMIZE__   _mm_clmulepi64_si128 is implemented
as always_inline function (surrounded by #pragma GCC target("pclmul")), so for
-O1+ the inlining error is expected, such function can't be inlined into the
current function, and always_inline mandates that it is inlined (without
always_inline it would simply not be inlined, and the out of line
_mm_clmulepi64_si128 would use the pclmul ISA, while the caller would not).

For -O0, this is implemented using a macro, since the last argument must be a
constant, and the reason you get no error is that the function is const and you
don't use the result, so it is DCEd.
If you actually use the result (at -O0 it is enough to store it into say
__m128i c = _mm_clmulepi64_si128(a, b, 1); , for -O1 you'd need something
better, store into volatile var, or global var or otherwise make sure it isn't
DCEd), then you get this diagnosed:

/tmp/z.c: In function ‘main’:
/tmp/z.c:6:11: error: ‘__builtin_ia32_pclmulqdq128’ needs isa option -m32
-mpclmul
   __m128i c = _mm_clmulepi64_si128(a, b, 1);
           ^

So I don't see any bug on the gcc side here.
>From gcc-bugs-return-472775-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Mon Jan 12 10:10:57 2015
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Subject: [Bug libstdc++/64535] Emergency buffer for exception allocation too small
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd535

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
If all allocations from the emergency pool are at least
sizeof(__cxa_refcounted_exception) long (or what is the minimum), then trying
to split the memory into smaller chunks (down to sizeof(free_entry)) might be
counter-productive.