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[compiler-rt][PowerPC] missing IEEE long double emulation functions #89054
Description
Activity
@llvm/issue-subscribers-backend-powerpc
Author: Piotr Kubaj (pkubaj)
Details
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).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!
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
__cmpukf2and__cmpokf2are not found insidellvmsubdirectory, the rest libcalls may be generated by LLVM backend but compiler-rt does not have implementations.@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).While I succeeded in creating a workaround on FreeBSD's side, this issue came up while upstreaming at #201298. What would be the preferred way of adding this support? I can see two ways:
a) small per-symbol wrappers underlib/builtins/ppc/that#definethetfentry point to thekfname and#includethe existing binary128 source with the working type forced to__float128/_Float128; or
b) a dedicated PPCkfbuild of the binary128 builtins, closer to libgcc'st-float128.brad0 commented
on Oct 9, 2026
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).