[LLVMdev] instructions requiring specific physical registers for operands

Jonas Paulsson
Wed, 09 May 2012 10:54:15 -0000

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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