Undeclared HWCAP_CRC32 compilation error in ARMv8 (Jetson TX2)

[cdsousa]

I'm getting this error:
/home/nvidia/julia/src/crc32c.c:336:17: error: 'HWCAP_CRC32' undeclared (first use in this function)
when compiling Julia master, at a0180d9, in a Jetson TX2 (ARMv8).
Two months older versions used to compile flawlessly.

[vchuravy]

The last change to that file was in October. What C/C++ compiler are you using, and did you maybe update your compiler in the mean time?

[stevengj]

This line was added in #22385; HWCAP_CRC32 should be defined in your compiler's hwcap.h file

[yuyichao]

Not sure what changed but try adding # include <hwcap.h> here ?

[yuyichao]

Actually that shouldn't be needed I haven't found the aarch64 definition yet but According to https://github.molgen.mpg.de/git-mirror/glibc/blob/20003c49884422da7ffbc459cdeee768a6fee07b/sysdeps/unix/sysv/linux/arm/bits/hwcap.h#L20 including auxv.h is the correct way.

[yuyichao]

Found it. It was added 2 years ago in bminor/glibc@26c2910 and the usage we have seems correct. What's your glibc version and what's your bits/hwcap.h ? (should be /usr/include/bits/hwcap.h)

[cdsousa]

Thanks.
Running the gcc command with -M:

nvidia@tegra-ubuntu:~/julia/src$ gcc -march=armv8-a -fasynchronous-unwind-tables -DJULIA_ENABLE_THREADING -DJULIA_NUM_THREADS=1 -std=gnu99 -pipe -fPIC -fno-strict-aliasing -D_FILE_OFFSET_BITS=64 -Wold-style-definition -Wstrict-prototypes -Wc++-compat -O3 -ggdb2 -falign-functions -D_GNU_SOURCE -I. -I/home/nvidia/julia/src -I/home/nvidia/julia/src/flisp -I/home/nvidia/julia/src/support -I/home/nvidia/julia/usr/include -I/home/nvidia/julia/usr/include -DLIBRARY_EXPORTS -I/home/nvidia/julia/deps/valgrind -Wall -Wno-strict-aliasing -fno-omit-frame-pointer -fvisibility=hidden -fno-common -Wpointer-arith -Wundef -DJL_BUILD_ARCH='"aarch64"' -DJL_BUILD_UNAME='"Linux"' -I/home/nvidia/julia/usr/include -DLLVM_SHLIB "-DJL_SYSTEM_IMAGE_PATH=\"../lib/julia/sys.so\"" -DNDEBUG -DJL_NDEBUG -c /home/nvidia/julia/src/crc32c.c -M 

entails:

crc32c.o: /home/nvidia/julia/src/crc32c.c /usr/include/stdc-predef.h \
 /home/nvidia/julia/src/julia.h \
 /home/nvidia/julia/src/support/libsupport.h \
 /home/nvidia/julia/src/support/platform.h /usr/include/stdlib.h \
 /usr/include/features.h /usr/include/aarch64-linux-gnu/sys/cdefs.h \
 /usr/include/aarch64-linux-gnu/bits/wordsize.h \
.....................................
(many other headers)
......................................
 /home/nvidia/julia/usr/include/libunwind-common.h \
 /home/nvidia/julia/usr/include/libunwind-dynamic.h \
 /usr/include/aarch64-linux-gnu/sys/auxv.h /usr/include/elf.h \
 /usr/include/aarch64-linux-gnu/bits/auxv.h \
 /usr/include/aarch64-linux-gnu/bits/hwcap.h \
 /home/nvidia/julia/src/crc32c-tables.c

In fact /usr/include/aarch64-linux-gnu/bits/hwcap.h does not define anything nor includes any other file.

In the system there is a /usr/src/linux-headers-4.4.38-tegra/arch/arm64/include/asm/hwcap.h which includes /usr/src/linux-headers-4.4.38-tegra/arch/arm64/include/uapi/asm/hwcap.h which has a HWCAP_CRC32.

File /usr/include/aarch64-linux-gnu/bits/hwcap.h comes from package libc6-dev which has version 2.23-0ubuntu10.

[cdsousa]

There is also a /usr/include/aarch64-linux-gnu/asm/hwcap.h file which has HWCAP_CRC32.

[cdsousa]

/usr/include/aarch64-linux-gnu/bits/hwcap.h
only has

\\ (initial comments)

#ifndef _SYS_AUXV_H
# error "Never include <bits/hwcap.h> directly; use <sys/auxv.h> instead."
#endif

/* No bits defined for this architecture.  */

[yuyichao]

It seems that your glibc is just a little too old. Note that including the kernel header usually isn't a solution due to possible name conflict with glibc ones.

One solution is to do a ifdef check and if not, define our own value. (it's a kernel API so the value is stable).

Another solution is to just use processor.h, which already have this value hard coded.
Does it work if you add #include "processor.h" here and replace the use of HWCAP_CRC32 with JL_AArch64_crc?

[yuyichao]

Actually, should be (1 << JL_AArch64_crc).

[cdsousa]

Ok, guess that what I had compiled two months ago was in fact v0.6.2. That compiles since its source code does not uses HWCAP_CRC32.

Doing

#include "processor.h"
#define HWCAP_CRC32 (1 << JL_AArch64_crc)

works.
But now I'm bumping into another, unrelated, error:

ERROR: Invalid CPU name armv8-a.
Makefile:195: recipe for target '/home/nvidia/julia/usr/lib/julia/basecompiler.ji' failed

[vchuravy]

JULIA_CPU_TARGET=generic
MARCH=armv8-a

should do the trick.

[yuyichao]

#define HWCAP_CRC32 (1 << JL_AArch64_crc)

Don't do that, replace the actual use.

ERROR: Invalid CPU name armv8-a.

That doesn't make much sense..... There's only one place that can set the flag to cause this which is arg_target_data(const TargetData<feature_sz> &arg, bool require_host) and it can only happen if auto spec = find_cpu(res.name) fails. So you should set a breakpoint there to see why it didn't find the info corresponding to the valid name "armv8-a".