NEON intrinsics not available with the soft-float ABI

[smessmer]

Details: https://github.com/cryfs/cryfs/issues/408

Trying to build CryFS 0.11.0 and 0.11.1 (which uses CryptoPP 8.5 and 8.6 respectively) fails on armel while CryFS 0.10.x (which uses CryptoPP 8.2) works fine.

The error message is

...
[  3%] Building CXX object vendor/cryptopp/vendor_cryptopp/CMakeFiles/cryptopp-object.dir/aria_simd.cpp.o
In file included from /<<PKGBUILDDIR>>/vendor/cryptopp/vendor_cryptopp/aria_simd.cpp:18:
/usr/lib/gcc/arm-linux-gnueabi/11/include/arm_neon.h:31:2: error: #error "NEON intrinsics not available with the soft-float ABI.          Please use -mfloat-abi=softfp or -mfloat-abi=hard"
   31 | #error "NEON intrinsics not available with the soft-float ABI.  Please use -mfloat-abi=softfp or -mfloat-abi=hard"
      |  ^~~~~
/<<PKGBUILDDIR>>/vendor/cryptopp/vendor_cryptopp/aria_simd.cpp:67:34: error: ‘uint32x4_t’ does not name a type; did you mean ‘uint32_t’?
   67 | inline void ARIA_GSRK_NEON(const uint32x4_t X, const uint32x4_t Y, byte RK[16])
      |                                  ^~~~~~~~~~
      |                                  uint32_t
/<<PKGBUILDDIR>>/vendor/cryptopp/vendor_cryptopp/aria_simd.cpp:67:54: error: ‘uint32x4_t’ does not name a type; did you     mean ‘uint32_t’?
...

This was reported by the maintainer of the CryFS debian packages, it fails while trying to build the packages for Debian APT.

Any ideas on what could cause this?

[noloader]

Thanks @smessmer,

Any ideas on what could cause this?

We made some changes for Clang and I suspect this break is due to it. The changes happened a while ago, but I suspect the problem surfaced recently under GCC 11.

I try to get it cleared this week.

Also see GH #1094. I think its the same problem.

[noloader]

@smessmer,

Sorry about the late reply.

For armel, would it be possible for you to add CRYPTOPP_DISABLE_ARM_NEON to your CPPFLAGS. Something like:

$ CPPFLAGS="-DCRYPTOPP_DISABLE_ARM_NEON" make 
Using testing flags: -DCRYPTOPP_DISABLE_ARM_NEON
g++ -DCRYPTOPP_DISABLE_ARM_NEON -DNDEBUG -g2 -O3 -fPIC -pthread -c cryptlib.cpp
g++ -DCRYPTOPP_DISABLE_ARM_NEON -DNDEBUG -g2 -O3 -fPIC -pthread -c cpu.cpp
g++ -DCRYPTOPP_DISABLE_ARM_NEON -DNDEBUG -g2 -O3 -fPIC -pthread -c integer.cpp
...
g++ -DCRYPTOPP_DISABLE_ARM_NEON -DNDEBUG -g2 -O3 -fPIC -pthread -c aria.cpp
g++ -DCRYPTOPP_DISABLE_ARM_NEON -DNDEBUG -g2 -O3 -fPIC -pthread -march=armv7-a -mfpu=neon -c aria_simd.cpp
g++ -DCRYPTOPP_DISABLE_ARM_NEON -DNDEBUG -g2 -O3 -fPIC -pthread -c ariatab.cpp
...

It seems to be testing OK on my RPI1, which is an ARMv6 machine without NEON. The options for aria_simd.cpp are kind of weird. I'll need to look at that a little more. But the code path causing the compile failure should be removed.

I have not gotten to link yet. A link problem could rise up on us. Its going to take a few hours to get the full result back on this old Pi.

CRYPTOPP_DISABLE_ARM_NEON is no loss since you don't have NEON anyways. NEON will be available on armhf platforms. That's where we want NEON in effect.

---

The trouble I've been having is, I can't seem to reliable determine a non-NEON platform, like armel.

pi@rpi1:~ $ uname -m
armv6l
pi@rpi1:~ $ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description:    Raspbian GNU/Linux 10 (buster)
Release:        10
Codename:       buster

[noloader]

@smessmer,

The options for aria_simd.cpp are kind of weird. I'll need to look at that a little more. But the code path causing the compile failure should be removed.

This oddity should be cleared with Commit 66d73d6d8b95.

[noloader]

@smessmer,

The tip of Master is fixed. We also got a bunch of CMake problems ironed out.

If you can wait about a week or two, then I'll release Crypto++ 8.7.

Or, you should be able to go with Crypto++ 8.6 but build with -DCRYPTOPP_DISABLE_ARM_NEON defined. armel should be built with -DCRYPTOPP_DISABLE_ARM_NEON but it failed to do so. If you add -DCRYPTOPP_DISABLE_ARM_NEON manually, then you are doing what the build system should have done.

Crypto++ 8.6 may need Commit 4473b50803d0.