[LLVMdev] [RFC] Replacing EVT:s with MVT:s (when possible)

David Chisnall david.chisnall at cl.cam.ac.uk
Wed Dec 5 04:51:13 PST 2012

On 3 Dec 2012, at 23:45, Chris Lattner wrote:

> Please do.  MVT is cheaper than EVT and conceptually cleaner when dealing with physical machine types.  EVT should only be used in parts of the code generator that are "pre-legalization" because they can represent arbitrary IR types.  Anything that takes a legal machine type should take an MVT.

A side issue of this is that it is currently relatively hard to add new machine-specific register types.  The only way of doing this involves extending MVT, which requires tweaking three files in the (nominally) target-independent parts of the compiler.  It would be great if we could simply reserve a (small?) number of MVTs for target-specific legal values.


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