IRGen: simplify getSpareBitsForType #23442
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Use an APInt to create the spare bit mask for integer values. This will allow us to byte swap it when we make the SpareBitVector strictly little-endian even when targeting big-endian machine. While editing this code I've also got rid of the goto statement since it seemed unnecessary.
mundaym
commented
Mar 20, 2019
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| // Round Integer-Of-Unusual-Size types up to their allocation size. | ||
| unsigned allocBits = size.getValueInBits(); | ||
| assert(allocBits >= intTy->getBitWidth()); |
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I dropped this assertion since llvm::APInt::getBitsSetFrom already asserts this and the earlier DataLayout assertion will catch it first anyway probably.
jckarter
approved these changes
Mar 20, 2019
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@swift-ci Please test |
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My plan is to make non-functional changes similar to this PR everywhere in IRGen where I think we need to byte swap raw bit patterns on big-endian platforms. This will usually involve
SpareBitVectoruses being replaced with an appropriately sizedAPIntso that a byte swap can be done. Eventually we'd perhaps replaceSpareBitVectorwithAPInteverywhere as per @jckarter's comment in https://forums.swift.org/t/fixing-enums-on-big-endian-systems/21730/3 but I think it would be good to do that in stages.