[llvm-dev] How to remove memcpy

[Wolfgang McSneed via llvm-dev]

Hi Mehdi and Joerg,

Thanks for your fast response! attached is the matrix_float.c file.

Also - I should point out that I am using MIPS ISS.

Thanks,

Wolf

Kind Regards,

Wolf

On Sat, Oct 15, 2016 at 6:07 PM, Joerg Sonnenberger via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On Sat, Oct 15, 2016 at 04:01:36PM -0700, Mehdi Amini via llvm-dev wrote:
> >
> > > On Oct 15, 2016, at 3:56 PM, Wolfgang McSneed via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> > >
> > > Hi,
> > >
> > > I am hoping that someone can help me figure out how to prevent the
> insertion of "memcpy" from the assembly source.
> > >
> > > My target is an instruction set simulator that doesn't support this.
> > >
> > > Thank you for your valuable time.
> > >
> > > Wolf
> > >
> > > Here are my compile commands:
> > > $ clang -emit-llvm -fno-builtin -o3 --target=mips -S matrix_float.c -o
> vl_matrix_float.ll
> >
> > Technically  -fno-bultin prevents the compiler from understand the
> > memset in the original code. The right option to prevent the compiler
> > from insert libc calls “out-of-the-blue” is -ffreestanding.
>
> Huh? The -fno-builtin is not the problem. The compiler is *expected* to
> call certain functions even for -ffreestanding. memcpy and memset are
> two of those. It is certainly perfectly valid target lowering for
> llvm.memcpy to be turned back into a libcall.
>
> Joerg
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