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...constraint on register > allocation > that is potentially bad. Fernando and Anton have already answered this question. The allocator creates new intervals for spill / restore and they are just like other intervals (except they are not allowed to spill again). So to sum up. The code in VirtMap is not really performing the spilling. It's mostly just doing the rewrite. Evan > > For example, the prototype graph coloring allocator posted by Bill > W. some > time ago has this code in it (the **** comments are my own): > > /// SpillLiveInterval - Assign a live inter...

Can someone explain the theory behind the spillers in VirtRegMap.cpp? It seems as though the spillers do triple duty: - Insert load/store operations and/or fold instructions as necessary to carry out spills - Rewrite the spilled virtual registers to use machine registers (mapping given by the caller in the VRM). - Rewrite machine code to change virtual registers to physical registers