Date: Fri, 9 Sep 2016 13:45:57 -0500 From: Krzysztof Parzyszek <kristof@swissmail.org> To: 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: <74556e62-cc12-a4c7-53f4-0be7ec01163f@swissmail.org> In-Reply-To: <6EA51424-C360-4604-B2D5-06C6762600A9@dsl-only.net> References: <EB82D9DC-4868-4075-B02E-BEC3A241C9A9@dsl-only.net> <6EA51424-C360-4604-B2D5-06C6762600A9@dsl-only.net>
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On 9/8/2016 8:02 PM, Mark Millard wrote: > > Interestingly http://compiler-rt.llvm.org says (mentioning powerpc64 explicitly): > > [Quoting the web site this time.] > >> Platform Support >> >> builtins is known to work on the following platforms: >> >> • Machine Architectures: i386, X86-64, SPARC64, ARM, PowerPC, PowerPC 64. >> • OS: AuroraUX, DragonFlyBSD, FreeBSD, NetBSD, Linux, Darwin. > > If true for all builtins (libgcc like) for powerpc64 then I'm not sure why there is the code: > > [Quoting from https://reviews.llvm.org/D13351 and its cfe/trunk/lib/Driver/Tools.cpp material this time.] > >> ppc::FloatABI FloatABI = ppc::getPPCFloatABI(D, Args); >> if (FloatABI == ppc::FloatABI::Soft && >> !(Triple.getArch() == llvm::Triple::ppc64 || >> Triple.getArch() == llvm::Triple::ppc64le)) >> Features.push_back("+soft-float"); >> else if (FloatABI == ppc::FloatABI::Soft && >> (Triple.getArch() == llvm::Triple::ppc64 || >> Triple.getArch() == llvm::Triple::ppc64le)) >> D.Diag(diag::err_drv_invalid_mfloat_abi) >> << "soft float is not supported for ppc64"; > > The above reports that "soft float is not supported for ppc64". This notice seems to be global for clang powerpc64: in no way FreeBSD specific. > > May be the view is that no floating point builtins ever apply to powerpc64 (but they do for powerpc (32))? I think the reasoning was that all powerpc64 cores do contain floating-point units (and that the 64-bit part wasn't tried/tested/etc). I have looked at compiler-rt and it does have support for all floating-point operations (although it seems to only do rounding-to-nearest). On a somewhat related note---the kernel does have some sort of an FPU emulation---do you know what it's for and how it's used? It does make more sense to use compiler-supported library though, after all it's the compiler generating calls to it. -Krzysztof
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