[llvm-commits] [llvm] r109449 - /llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp

[Eric Christopher]

On Jul 26, 2010, at 3:31 PM, Evan Cheng wrote:

> By definition register pressure tracking in the scheduler is an approximation. We're not modeling live throughs, nor are we taking into consideration special register allocation requirement, etc.
> 
> The other major issue is register pressure excess for different register classes are the same. e.g. let's say node A will cause high GPR register pressure, node B VR128. The scheduler doesn't know whether it's better to schedule A or B first.

Aha.  Excellent, thanks.

-eric