llvm dev - Mar 2011 - [LLVMdev] MachineOperand type

Hi all,

I have a question about the types of MachineOperand. There are 12 
different types of MachineOperand such as MO_Register, MO_Immediate and 
so on. Some of the names are self-explanatory such as MO_Register and 
MO_Immediate. Some of them are a little confusing such as MO_FrameIndex, 
MO_ConstantPoolIndex and so on. For example, what is the different 
between MO_ExternalSymbol and MO_GlobalAddress? Are these two types 
orthogonal? I found that memset and memcpy are MO_ExternalSymbol and 
printf and fprintf and so on are MO_GlobalAddress.

Thanks a lot in advance. Any advice will be greatly appreciated.

Bin

On Mar 2, 2011, at 8:34 PM, Bin Zeng wrote:
> Hi all,
> 
> I have a question about the types of MachineOperand. There are 12 
> different types of MachineOperand such as MO_Register, MO_Immediate and 
> so on. Some of the names are self-explanatory such as MO_Register and 
> MO_Immediate. Some of them are a little confusing such as MO_FrameIndex, 
> MO_ConstantPoolIndex and so on. For example, what is the different 
> between MO_ExternalSymbol and MO_GlobalAddress? Are these two types 
> orthogonal? I found that memset and memcpy are MO_ExternalSymbol and 
> printf and fprintf and so on are MO_GlobalAddress.
> 
> Thanks a lot in advance. Any advice will be greatly appreciated.
GlobalAddress is used to refer to something that exists in IR, such as a global
variable.  ExternalSymbol is used to refer to something that isn't in the IR
because it was synthesized by codegen, such as __addsi3.

-Chris

On Mar 3, 2011, at 2:30 PM, Bin Zeng wrote:
>>> 
>>> Thanks a lot in advance. Any advice will be greatly appreciated.
>> GlobalAddress is used to refer to something that exists in IR, such as
a global variable.  ExternalSymbol is used to refer to something that isn't
in the IR because it was synthesized by codegen, such as __addsi3.
>> 
>> -Chris
> 
> Thanks for the quick reply. According to your reply, memset and memcpy are
synthesized by codegen? I saw memcpy in the source file. Did it get optimized
out in the IR and later codegen synthesized memset and memcpy?
Yes, codegen does synthesize memcpy in some cases, also memset.

-Chris