[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

[Dale Johannesen]

On Sep 30, 2008, at 4:13 PMPDT, Evan Cheng wrote:

> Actually no.  It's a terrible idea. :-)
>
> This logic should not be in codegen at all. Users can still right
> __builtin_memcpy and those can be optimized with -fno-builtin.
>
> So correct solution, take two. :-) FE should not generate calls to
> @llvm.memset.i32 etc. when -fno-builtin is specified. Instead, it
> should generate a simple call to memset. So the only changes required
> are in the FE, LLVM should not know anything about -fno-builtin at
> all.

Right.

> That is, unless simplifylibcall decides to turn memset into
> @llvm.memset*.

This is why simplifylibcall shouldn't be keying off names.  I don't  
think I got through before, maybe now....

> Evan
>
> On Sep 30, 2008, at 4:08 PM, Bill Wendling wrote:
>
>> On Tue, Sep 30, 2008 at 3:55 PM, Evan Cheng <evan.cheng at apple.com>
>> wrote:
>>>
>>> Actually, I think it'd be better to do this the right way.
>>
>> Bah! :-)
>>
>>> The correct
>>> way to handle this option is to convert all memcpy / memset (and
>>> other) intrinsic calls to normal calls. Perhaps in
>>> SelectionDAGBuild.cpp? e.g.
>>>
>>> case Intrinsic::memcpy_i32:
>>> case Intrinsic::memcpy_i64: {
>>>   SDValue Op1 = getValue(I.getOperand(1));
>>>   SDValue Op2 = getValue(I.getOperand(2));
>>>   SDValue Op3 = getValue(I.getOperand(3));
>>>   unsigned Align = cast<ConstantInt>(I.getOperand(4))-
>>>> getZExtValue();
>>>   DAG.setRoot(DAG.getMemcpy(getRoot(), Op1, Op2, Op3, Align, false,
>>>                             I.getOperand(1), 0, I.getOperand(2),
>>> 0));
>>>   return 0;
>>> }
>>>
>>> We can lower it to a call to memcpy with -fno-builtin.
>>>
>> That's basically what I suggested in another email. So I think it's a
>> brilliant idea. ;-)
>>
>> -bw
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