refactor: retrieve immediates in new backend #2251
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abrown
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cfallin
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bjorn3
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This is no change to functionality; the move is necessary in order to return InstructionData immediates in a structure way (see next commit).
This change abstracts away (from the perspective of the new backend) how immediate values are stored in InstructionData. It gathers large immediates from necessary places (e.g. constant pool) and delegates to `InstructionData::imm_value` for the rest. This refactor only touches original users of `LowerCtx::get_immediate` but a future change could do the same for any place the new backend is accessing InstructionData directly to retrieve immediates.
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As discussed in bytecodealliance#2251, in order to be very confident that NaN signaling bits are correctly handled by the compiler, this switches `DataValue` to use Cranelift's `Ieee32` and `Ieee64` structures. This makes it a bit more inconvenient to interpreter Cranelift FP operations but this should change to something like `rustc_apfloat` in the future.
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abrown
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As discussed in bytecodealliance#2251, in order to be very confident that NaN signaling bits are correctly handled by the compiler, this switches `DataValue` to use Cranelift's `Ieee32` and `Ieee64` structures. This makes it a bit more inconvenient to interpreter Cranelift FP operations but this should change to something like `rustc_apfloat` in the future.
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As discussed in #2251, in order to be very confident that NaN signaling bits are correctly handled by the compiler, this switches `DataValue` to use Cranelift's `Ieee32` and `Ieee64` structures. This makes it a bit more inconvenient to interpreter Cranelift FP operations but this should change to something like `rustc_apfloat` in the future.
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@cfallin, here is what I came up with after we discussed this last week. This change:
DataValueinto cranelift-codegen so that I can use it as a value wrapperInstructionDatathe ability to find immediate values in the format structuresLowerCtx::get_immediateto grab the value from the instruction (and the DataFlowGraph for vector immediates)I felt like this approach provides the new backend a more abstract view of immediates instead of munging directly in the
InstructionDatabut I didn't perform the refactor on the rest of the places the new backend grabs immediates because I wanted to get some feedback first.