[PATCH] D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64

Wed Apr 10 08:01:27 PDT 2019

manojgupta added a comment.

In D60472#1461351 <https://reviews.llvm.org/D60472#1461351>, @peter.smith wrote:

>

> Is that not a limitation of the build system? I'd expect a package to be able to locally override a global default rather than vice-versa. Although crypto might be the area of concern here and there may be a conveniently named option for PPC, where does this stop? Crypto is not the only architectural extension, for example see https://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html . To maintain a consistent interface we'd need command line options for all the extensions. May I encourage you to reply to the RFC on command line options that I mentioned earlier if it doesn't work for you? I think the extensions need to be considered as a whole and not just individually.

While it partly is a build system issue, another problem is enabling crypto via "-march" requires picking an architecture as well. So even if it could override the global default, it would also override the global "-march" as well. If the global "-march" was a better/higher option, it does not make sense to override it e.g. "-march=armv8-a+crypto" overriding "-march=armv8.3-a" is not helpful since it will disable 8.3 features.

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https://reviews.llvm.org/D60472