[libcxx-commits] [PATCH] D137513: [libc++] Replace __ppc64__ with __powerpc64__

[Fangrui Song via Phabricator via libcxx-commits]

MaskRay added a comment.

In D137513#3912878 <https://reviews.llvm.org/D137513#3912878>, @q66 wrote:

> (this patch also accounts for glibc setups that use the real quad-precision ieee754 long doubles, which is possible since some time ago, natively in hardware starting with POWER9 - e.g. fedora defaults to that now, as far as i know - the logic here checks for two conditions - having a larger exponent indicates real ieee754 quad float as double-double's is identical to double, while having the same amount of mantissa digits indicates that long double is equal to double)

I think there are 3 modes.

- `-mlong-double-64`
- `-mlong-double-128 -mabi=ieeelongdouble`
- `-mlong-double-128 -mabi=ibmlongdouble`

If `-mlong-double-128 -mabi=ieeelongdouble` should define `is_iec559` as well, we can detect IBM128 with `defined(__LONG_DOUBLE_IBM128__)`.


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  https://reviews.llvm.org/D137513/new/

https://reviews.llvm.org/D137513