LTO apparently does not support _FloatNx types

[Paul Iannetta]

Hi,

I was investigating an ICE (in our yet to be upstreamed back-end which
has native support for float16), on "gcc.dg/torture/float16-complex.c"
when compiled with lto:

./gcc/build/gcc/xgcc -B./gcc/build/gcc/ ./gcc/gcc/testsuite/gcc.dg/torture/float16-complex.c \
-O2 -flto -fno-use-linker-plugin -flto-partition=none -lm -o ./float16-complex.exe

I narrowed it down to the fact that lto-lang does not support _FloatNx
types, the function "lto_type_for_mode" (in gcc/lto/lto-lang.c) and
"c_common_type_for_mode" (in gcc/c-family/c-common.c) are exactly the
same except that "lto_type_for_mode" does not support _FloatNx.

Is this intentional or an oversight?

Cheers,
Paul