[compiler-rt][PowerPC] missing IEEE long double emulation functions

[pkubaj]

Currently when building LLVM on ppc64le with IEEE long double, LLVM tries to use emulation functions listed in https://gcc.gnu.org/wiki/Ieee128PowerPC (table in 2.3 Emulation functions). However, compiler-rt has no implementation of those functions leading to a build failure when there's no libgcc installed (e.g. on LLVM-only system).

[llvmbot]

@llvm/issue-subscribers-backend-powerpc

Author: Piotr Kubaj (pkubaj)

Currently when building LLVM on ppc64le with IEEE long double, LLVM tries to use emulation functions listed in https://gcc.gnu.org/wiki/Ieee128PowerPC (table in 2.3 Emulation functions). However, compiler-rt has no implementation of those functions leading to a build failure when there's no libgcc installed (e.g. on LLVM-only system).

[chenzheng1030]

Could you share your usage for LLVM-only system? It it a Linux system? Why do you want to try with LLVM-only system? Thank you!

[ecnelises]

From the table, following supplementary functions are for __float128 (LLVM does not support decimal so they are excluded):

• __extendsfkf2
• __extenddfkf2
• __trunckfsf2
• __trunckfdf2
• __extendkftf2
• __trunctfkf2
• __floatsikf
• __floatdikf
• __floatdikf
• __floattikf
• __floatunsikf
• __floatundikf
• __floatundikf
• __floatuntikf
• __addkf3
• __subkf3
• __mulkf3
• __divkf3
• __cmpukf2
• __cmpokf2

Except __cmpukf2 and __cmpokf2 are not found inside llvm subdirectory, the rest libcalls may be generated by LLVM backend but compiler-rt does not have implementations.

[pkubaj]

@chenzheng1030
FreeBSD is LLVM-only. We use clang as C compiler, clang++ as C++ compiler, lld as linker and libc++ as a C++ standard library. Our C library is our own (no glibc nor musl).