Date: Wed, 7 Sep 2016 19:42:13 -0700 From: Mark Millard <markmi@dsl-only.net> To: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: From llvm: Fwd: [Bug 26519] Clang 3.8.0's "Target: powerpc-unknown-freebsd11.0" code generation is violating the SVR4 ABI (SEGV can result) [fixed in llvm -r280705] Message-ID: <BF0692B3-495A-42A5-B37E-55E1CD7F16AD@dsl-only.net>
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Krzysztof Parzyszek kristof at swissmail.org wrote on Wed Sep 7 23:03:03 UTC 2016 > What about this? https://reviews.llvm.org/D13351 > > > -Krzysztof > > On 9/7/2016 5:50 PM, Krzysztof Parzyszek wrote: > > What are the requirements for soft-float, i.e. what conditions exactly > > does the generated code need to meet? Is the purpose of it to eliminate > > the use of floating point registers? > > > > Is there a library that implements the floating point operations? If > > not, that is going to be the main obstacle. > > > > -Krzysztof https://reviews.llvm.org/D13351 is for ppc32 (TARGET_ARCH=powerpc in FreeBSD terms), not ppc64 (TARGET_ARCH=powerpc64 in FreeBSD terms). As Justin Hibbits wrote in answer to what soft-float is used for: > Soft float is required when building the kernel to prevent the compiler from using floating point optimizations. > > - - Justin I think that "optimizations" here means (in part?) avoiding the floating point hardware as the kernel need not save/restore the registers and the like for its own activities. Only user-space gets that service as I understand. I have used clang/clang++ to do a partially-working FreeBSD buildworld for TARGET_ARCH=powerpc (ppc32) based on https://reviews.llvm.org/D13351 material having been included in clang 3.8.0. (I had to temporarily modify the kernel to have a so-called "red-zone" on the stack for signal delivery, effectively stepping outside FreeBSD's TARGET_ARCH=powerpc related ABI standard.) But TARGET_ARCH=powerpc64 just reports that clang does not have softfloat and the build stops as things are. === Mark Millard markmi at dsl-only.nethelp
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