[LLVMdev] Doubts about lowering of UMUL_LOHI

[Sachin.Punyani at microchip.com]

Hi,

 

When expanding multiply operation in LegalizeTypes LLVM generates some
nodes such as UMUL_LOHI (please refer file LegalizeIntegerTypes.cpp -
function - ExpandIntegerResult).  However while lowering this operation
in LegalizeDAG (please refer file LegalizeDAG.cpp  - function -
LegalizeOp) the comment says 

 

"These nodes will only be produced by target-specific lowering.....". 

 

LLVM, therefore, does not call the LowerOperation for these operations.
Function setOperationAction(UMUL_LOHI, ValueType, Custom) does not work
for these nodes. 

 

 My Doubts

1)       Why is there such contradiction in the code and comment?

2)       Why is custom legalization of this node not allowed?

3)       My target does not have any instruction directly matching to
this operation. How should this node be legalized?

 

Regards

Sachin

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20081218/57d40f8b/attachment.html>