Disabling emitting x86_fp80/ppc_fp128 IR

Hi all,

I’m sure this has been answered somewhere but I can’t seem to find it. I’ve got an application that uses the long double type in a couple of places. Is there a way to prevent clang from emitting architecture-specific floating point types, i.e., “x86_fp80” & “ppc_fp128”, and instead force clang to only emit “fp128” types? It seems like LLVM’s backends can easily handle this by emitting soft floating point routines (defined in the “compiler-rt” project) for dealing with these types. However, I don’t want to force soft floating point routines for other types, i.e., “half”, “float” and “double”.

Thanks!

Hi all,

According to this thread (http://www.openwall.com/lists/musl/2016/03/11/18), clang does not support emitting architecture-independent “fp128” types for PowerPC & x86-64, but instead will only emit their architecture-specific long double types. One alternative the thread suggests is to to force GCC to demote long double types to be equivalent to normal 64-bit doubles. Is there a way to enforce this behavior using clang, i.e., force clang to emit IR “double” types for values declared as “long double” in the source code?

You can write "__float128" to get an fp128 on any target which supports it.

There is no option to modify the type of "long double"; ABI-changing options are generally dangerous (code compiled with the flag is incompatible with code compiled without it).

-Eli