Hi Corey, thanks for investigating.
Note that we use xlclang++ on AIX. It may possibly understand the directives as gcc on linux. Gcc 7.3.1 is the minimum for BE linux. But if you protect your code by #ifdef VM_LITTLE_ENDIAN no compiler except gcc >= 7.4.0 should ever look at it. Best regards, Martin > -----Original Message----- > From: Corey Ashford <cjash...@linux.ibm.com> > Sent: Dienstag, 1. September 2020 02:17 > To: Doerr, Martin <martin.do...@sap.com> > Cc: Michihiro Horie <ho...@jp.ibm.com>; hotspot-compiler- > d...@openjdk.java.net; core-libs-dev <core-libs-dev@openjdk.java.net>; > Kazunori Ogata <oga...@jp.ibm.com>; jos...@br.ibm.com > Subject: Re: RFR(M): 8248188: [PATCH] Add HotSpotIntrinsicCandidate and > API for Base64 decoding > > On 8/27/20 8:07 AM, Doerr, Martin wrote: > >>> I will use __attribute__ ((align(16))) instead of __vector, and make > >> them arrays of 16 unsigned char. > > Maybe __vectors works as expected, too, now. Whatever we use, I'd > appreciate to double-check the alignment e.g. by using gdb. > > I don't remember what we had tried and why it didn't work as desired. > > > I just now tried on gcc-7.5.0, declaring a __vector at 1, 2, 3, 8, 9, > and 15 byte offsets in a struct, trying to force a misalignment, but the > compiler realigned all of them on 16-byte boundaries. > > If someone decides to make the intrinsic work on AIX (big endian), and > compiles with 7.3.1, I don't know what will happen w.r.t. alignment, so > to be on the safe side, I will make the declarations 16-byte unsigned > char arrays with an align attribute. > > Looking a bit deeper, I see that the __vector type comes out of the C > preprocessor as: __attribute__((altivec(vector__))). It's part of the > compiler's basic set of predefined macros, and can be seen using this > command: > > % gcc -dM -E - < /dev/null | grep __vector > > #define __vector __attribute__((altivec(vector__))) > > Some information here: > https://gcc.gnu.org/onlinedocs/gcc/PowerPC-Type-Attributes.html > > I don't know if this is helpful or not, but it might answer part of your > question about the meaning of __vector. > > Regards, > > - Corey
