[llvm-dev] How to remove memcpy

[Flamedoge via llvm-dev]

Even with -ffreestanding LLVM generates memcpy/memset? Does this mean some
passes do not honor this flag? If you really wanted to prevent libcalls,
you could technically translate those memcpy/memset to loops in lowering.
Kevin

On Sat, Oct 15, 2016 at 4:10 PM, Wolfgang McSneed via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> 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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>> llvm-dev at lists.llvm.org
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>>
>
>
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