| Enumerator |
|---|
| Legal | The operation is expected to be selectable directly by the target, and no transformation is necessary.
|
| NarrowScalar | The operation should be synthesized from multiple instructions acting on a narrower scalar base-type.
For example a 64-bit add might be implemented in terms of 32-bit add-with-carry.
|
| WidenScalar | The operation should be implemented in terms of a wider scalar base-type.
For example a <2 x s8> add could be implemented as a <2 x s32> add (ignoring the high bits).
|
| FewerElements | The (vector) operation should be implemented by splitting it into sub-vectors where the operation is legal.
For example a <8 x s64> add might be implemented as 4 separate <2 x s64> adds. There can be a leftover if there are not enough elements for last sub-vector e.g. <7 x s64> add will be implemented as 3 separate <2 x s64> adds and one s64 add. Leftover types can be avoided by doing MoreElements first.
|
| MoreElements | The (vector) operation should be implemented by widening the input vector and ignoring the lanes added by doing so.
For example <2 x i8> is rarely legal, but you might perform an <8 x i8> and then only look at the first two results.
|
| Bitcast | Perform the operation on a different, but equivalently sized type.
|
| Lower | The operation itself must be expressed in terms of simpler actions on this target.
E.g. a SREM replaced by an SDIV and subtraction.
|
| Libcall | The operation should be implemented as a call to some kind of runtime support library.
For example this usually happens on machines that don't support floating-point operations natively.
|
| Custom | The target wants to do something special with this combination of operand and type.
A callback will be issued when it is needed.
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| Unsupported | This operation is completely unsupported on the target.
A programming error has occurred.
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| NotFound | Sentinel value for when no action was found in the specified table.
|
| UseLegacyRules | Fall back onto the old rules.
TODO: Remove this once we've migrated
|
