[LLVMdev] instructions requiring specific physical registers for operands

[Jonas Paulsson]

Hi,

I have som instructions that require the operand to be placed in exactly one physical register, and thus I have introduced a Just_a0 register class.

I have found that the register allocators / coalescer do not seem to care about this. In many cases they "run out of registers during register allocation". I have managed to avoid some problems, by inserting target move instructions in and out of this Just_a0 register class.

I wonder, what would be the best solution for instructions that require operands in a particular register, and even gives the result in a particular register?

/Jonas

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