[LLVMdev] Difficulty with reusing DAG nodes.

[Richard Osborne]

Richard Pennington wrote:
> Eli Friedman wrote:
>   
>> I haven't looked at the rest of the email carefully, but why aren't
>> you just implementing MULHU and MULHS?  There's no point to
>> implementing the *MUL_LOHI variants if the processor doesn't have
>> them.
>>     
>
> I have implemented MULHU and MULHS. But if I take out my *MUL_LOHI 
> stuff, the error I get is
>
> [~/ellcc/ellcc] main% ./nios2-elf-ecc -S test.c
> Cannot yet select: 0xaf93a34: i32,i32 = umul_lohi 0xaf9345c, 0xaf93924
>
> What could I be doing to make the code generator think that umul_lohi is 
> legal?
>
> -Rich
>   
In your target lowering you need to set the operation action for 
ISD::*MUL_LOHI to expand otherwise it will be assumed to be legal.

Richard