[llvm-dev] Custom Instruction Cost Model to LLVM RISC-V Backend

[Bandhav Veluri via llvm-dev]

Hi,

I’m working on a RISC-V architecture that has instruction costs different
from those in the default cost model. Is there an out-of-source way to
provide llc with custom cost model? Or, does this need a change in LLVM
backend?

Also, the cost model is not totally static. For example, loads from
0x1000-0x1ffc take 1 cycle, whereas loads from address > 0x80000000, take
10-100 cycles. Is it possible to model these costs in the scheduler?
Requiring programmer to define custom pointer types to mark pointers, to
one or the other address space, is okay. Is there a way to model different
costs for different pointer types?

Thank you,
Bandhav
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