[llvm] r230141 - Calling memmove on a MachineOperand is totally safe.

[Pete Cooper]

Ah. No worries then. Thanks for the explanation.

Pete

Sent from my iPhone

> On Feb 22, 2015, at 4:11 AM, Benjamin Kramer <benny.kra at gmail.com> wrote:
> 
> 
>> On 22.02.2015, at 01:58, Pete Cooper <peter_cooper at apple.com> wrote:
>> 
>> Are you sure this is safe? I thought register operands had use lists which memmove isn't going to know to update?
> 
> Yes, that's what the other code path in this function does. The path I changed is only used when the MachineInstr containing the operand is not part of a MachineFunction and thus has no use lists.
> 
> - Ben
> 
>> 
>> Pete
>> 
>> Sent from my iPhone
>> 
>>> On Feb 21, 2015, at 8:22 AM, Benjamin Kramer <benny.kra at googlemail.com> wrote:
>>> 
>>> Author: d0k
>>> Date: Sat Feb 21 10:22:48 2015
>>> New Revision: 230141
>>> 
>>> URL: http://llvm.org/viewvc/llvm-project?rev=230141&view=rev
>>> Log:
>>> Calling memmove on a MachineOperand is totally safe.
>>> 
>>> While it's not POD due to the user-defined constructor, it's still a trivially
>>> copyable type. No functional change.
>>> 
>>> Modified:
>>>  llvm/trunk/lib/CodeGen/MachineInstr.cpp
>>> 
>>> Modified: llvm/trunk/lib/CodeGen/MachineInstr.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineInstr.cpp?rev=230141&r1=230140&r2=230141&view=diff
>>> ==============================================================================
>>> --- llvm/trunk/lib/CodeGen/MachineInstr.cpp (original)
>>> +++ llvm/trunk/lib/CodeGen/MachineInstr.cpp Sat Feb 21 10:22:48 2015
>>> @@ -674,14 +674,8 @@ static void moveOperands(MachineOperand
>>> if (MRI)
>>>   return MRI->moveOperands(Dst, Src, NumOps);
>>> 
>>> -  // Here it would be convenient to call memmove, so that isn't allowed because
>>> -  // MachineOperand has a constructor and so isn't a POD type.
>>> -  if (Dst < Src)
>>> -    for (unsigned i = 0; i != NumOps; ++i)
>>> -      new (Dst + i) MachineOperand(Src[i]);
>>> -  else
>>> -    for (unsigned i = NumOps; i ; --i)
>>> -      new (Dst + i - 1) MachineOperand(Src[i - 1]);
>>> +  // MachineOperand is a trivially copyable type so we can just use memmove.
>>> +  std::memmove(Dst, Src, NumOps * sizeof(MachineOperand));
>>> }
>>> 
>>> /// addOperand - Add the specified operand to the instruction.  If it is an
>>> 
>>> 
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>