OpenBLAS 0.3.1 Compile Fails with IBM XL 16.1.0 Compiler on POWER8

[nmhamster]

Bug when trying to compile OpenBLAS 0.3.1 download using IBM XL 16.1 (C/C++ and Fortran compilers) on POWER8. It appears inline assembly does not compile correctly.

[ 26%] Building C object kernel/CMakeFiles/kernel.dir/CMakeFiles/sasum_k.c.o
In file included from /ascldap/users/sdhammo/openblas/OpenBLAS-0.3.1/build-power8/kernel/CMakeFiles/sasum_k.c:7:
In file included from /ascldap/users/sdhammo/openblas/OpenBLAS-0.3.1/kernel/power/sasum.c:50:
/ascldap/users/sdhammo/openblas/OpenBLAS-0.3.1/kernel/power/sasum_microk_power8.c:172:8: error: unknown register name 'vs32' in asm
       "vs32","vs33","vs34","vs35","vs36","vs37","vs38","vs39",

[martin-frbg]

Known problem, see #1248 - according to #1078 (comment) this is a limitation of the XL compiler.

[trudeaun]

IBM XL 16.1 uses clang technology, and so far, "vs" register names are unsupported by clang. As a workaround, you can use v0, …, v7, instead of "vs32", …, "vs39".

[martin-frbg]

Good to know - was this already the case with xlc 13, which was the subject of the earlier issues ? (I note another problem back then was lack of support for constraints like "=wa" (t0)" in this same file, sasum_mikrok_power.c , which kept me from doing the vs mass rename - #1078 (comment) )

[trudeaun]

For "vs" register names, my comment applies to xlc 13 as well. For the second problem related to constraints like "wa", unfortunately even the latest version of XL (16.1) does not support it yet. This feature request is in XL's backlog and hopefully it can be implemented soon.

[martin-frbg]

So are there equivalent constraints that xlc supports ? So far it looks like David Edelsohn's comment is still valid ...

[trudeaun]

Unfortunately, no. The currently supported constraints are listed on Knowledge Center. Sorry about that.

[martin-frbg]

I have added an entry to the faq in the wiki (thought I had done that already earlier).