[llvm] [Intrinsics][AArch64] Add intrinsic to mask off aliasing vector lanes (PR #117007)

[Sam Tebbs via llvm-commits]

================
@@ -23475,6 +23475,92 @@ Examples:
       %active.lane.mask = call <4 x i1> @llvm.get.active.lane.mask.v4i1.i64(i64 %elem0, i64 429)
       %wide.masked.load = call <4 x i32> @llvm.masked.load.v4i32.p0v4i32(<4 x i32>* %3, i32 4, <4 x i1> %active.lane.mask, <4 x i32> poison)
 
+.. _int_experimental_get_alias_lane_mask:
+
+'``llvm.experimental.get.alias.lane.mask.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic.
+
+::
+
+      declare <4 x i1> @llvm.experimental.get.alias.lane.mask.v4i1.i64.i64(i64 %ptrA, i64 %ptrB, i64 immarg %elementSize, i1 immarg %writeAfterRead)
+      declare <8 x i1> @llvm.experimental.get.alias.lane.mask.v8i1.i64.i64(i64 %ptrA, i64 %ptrB, i64 immarg %elementSize, i1 immarg %writeAfterRead)
+      declare <16 x i1> @llvm.experimental.get.alias.lane.mask.v16i1.i64.i32(i64 %ptrA, i64 %ptrB, i32 immarg %elementSize, i1 immarg %writeAfterRead)
+      declare <vscale x 16 x i1> @llvm.experimental.get.alias.lane.mask.nxv16i1.i64.i32(i64 %ptrA, i64 %ptrB, i32 immarg %elementSize, i1 immarg %writeAfterRead)
+
+
+Overview:
+"""""""""
+
+Create a mask representing lanes that do or not overlap between two pointers
+across one vector loop iteration.
+
+
+Arguments:
+""""""""""
+
+The first two arguments have the same scalar integer type.
+The final two are immediates and the result is a vector with the i1 element type.
+
+Semantics:
+""""""""""
+
+In the case that ``%writeAfterRead`` is true, the
+'``llvm.experimental.get.alias.lane.mask.*``' intrinsics are semantically
+equivalent to:
+
+::
+
+      %diff = (%ptrB - %ptrA) / %elementSize
+      %m[i] = (icmp ult i, %diff) || (%diff <= 0)
+
+Otherwise they are semantically equivalent to:
+
+::
+
+      %diff = abs(%ptrB - %ptrA) / %elementSize
+      %m[i] = (icmp ult i, %diff) || (%diff == 0)
+
+where ``%m`` is a vector (mask) of active/inactive lanes with its elements
+indexed by ``i``,  and ``%ptrA``, ``%ptrB`` are the two i64 arguments to
+``llvm.experimental.get.alias.lane.mask.*``, ``%elementSize`` is the first
+immediate argument, ``%abs`` is the absolute difference operation, ``%icmp`` is
+an integer compare and ``ult`` the unsigned less-than comparison operator. The
----------------
SamTebbs33 wrote:

Done.

https://github.com/llvm/llvm-project/pull/117007