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

[Jay Foad via llvm-commits]

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@@ -807,6 +807,23 @@ For an int eq predicate ``ICMP_EQ``, the syntax is:
 
    %2:gpr(s32) = G_ICMP intpred(eq), %0, %1
 
+Lanemask Operands
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jayfoad wrote:

Nit: Please spell it "LaneMask" (capital M) throughout this patch to match the existing codebase.

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