[llvm] [CodeGen] Add MO_LaneMask type and a new COPY_LANEMASK instruction (PR #151944)

[Jay Foad via llvm-commits]

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@@ -114,6 +114,11 @@ HANDLE_TARGET_OPCODE(REG_SEQUENCE)
 /// used to copy between subregisters of virtual registers.
 HANDLE_TARGET_OPCODE(COPY)
 
+/// COPY_LANEMASK - Target-independent register copy for active mask in 
+/// register as represented by the lanemask. This instruction cannot be 
+/// only used to copy from the subregisters of virtual registers.
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jayfoad wrote:

What does the "cannot be only used" part mean? Please clarify.

https://github.com/llvm/llvm-project/pull/151944