[LLVMdev] scoreboard hazard det. and instruction groupings

[Anshuman Dasgupta]

Hal,

On 6/11/2012 12:48 PM, Andrew Trick wrote:
> Ignoring compile time for a moment, I think an advantage of a DFA is modeling a situation where the hardware can assign resources to best fit the entire group rather then one instruction at a time. For example, if InstA requires either Unit0 or Unit1, and InstB requires Unit0, is {InstA, InstB} a valid group? Depending on your cpu, a DFA could either recognize that it's valid, or give you a chance to reorder the instructions within a group once they've been selected.
>

I would recommend the DFA mechanism as well from what you've described. 
It considers all permutations of mapping instructions to functional 
units. To add to what Andrew said, note that the DFA answers the 
question of whether there exists a legal mapping of a group of 
instructions to functional units. It does not, however, return a legal 
mapping. Will that be sufficient for what you want?

-Anshu