[llvm-commits] [llvm] r56885 - in /llvm/trunk: include/llvm/Target/TargetLowering.h lib/CodeGen/SelectionDAG/SelectionDAG.cpp lib/Target/X86/X86ISelLowering.cpp lib/Target/X86/X86ISelLowering.h lib/Target/X86/X86Subtarget.cpp lib/Target/X86/X86Su

[Bill Wendling]

On Tue, Sep 30, 2008 at 2:47 PM, Dan Gohman <gohman at apple.com> wrote:
>
> On Sep 30, 2008, at 2:22 PM, Bill Wendling wrote:
>
>> Author: void
>> Date: Tue Sep 30 16:22:07 2008
>> New Revision: 56885
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=56885&view=rev
>> Log:
>> Add the new `-no-builtin' flag. This flag is meant to mimic the GCC
>> `-fno-builtin' flag. Currently, it's used to replace "memset" with
>> "_bzero"
>> instead of "__bzero" on Darwin10+. This arguably violates the
>> meaning of this
>> flag, but is currently sufficient. The meaning of this flag should
>> become more
>> specific over time.
>
> First, -fno-builtin is only intended to apply to user calls. It is not
> intended to apply to libcalls that the compiler generates. For example,
> specifying -fno-builtin-memcpy does not tell the compiler not to
> generate calls to memcpy.
>
> Second, it looks like there is confusion about the leading underscores.
> The previous code used "__bzero" on Darwin 10, which is actually
> printed as "___bzero" because of Darwin ABI rules. By introducing new
> code that uses "_bzero", it will be printed as "__bzero" on Darwin,
> which doesn't seem to be what was intended here.
>
That's what was intended.

> And furthermore, if "bzero" was intended, meaning printing in the
> output as "_bzero" on Darwin, that's an even more flagrant abuse of
> the -fno-builtin flag.  -fno-builtin doesn't mean that the compiler can
> call functions with names in the user namespace not reserved by the C
> standard.
>
I would have loved to do that, but people had problems with it.

-bw