[clang] [llvm] [AArch64][SVE] Change the immediate argument in svextq (PR #115340)

[via cfe-commits]

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@@ -2286,7 +2286,7 @@ let SVETargetGuard = "sve2p1", SMETargetGuard = InvalidMode in {
   def SVTBLQ : SInst<"svtblq[_{d}]", "ddu", "cUcsUsiUilUlbhfd", MergeNone, "aarch64_sve_tblq">;
   def SVTBXQ : SInst<"svtbxq[_{d}]", "dddu", "cUcsUsiUilUlbhfd", MergeNone, "aarch64_sve_tbxq">;
   // EXTQ
-  def EXTQ : SInst<"svextq[_{d}]", "dddk", "cUcsUsiUilUlbhfd", MergeNone, "aarch64_sve_extq", [], [ImmCheck<2, ImmCheck0_15>]>;
+  def EXTQ : SInst<"svextq[_{d}]", "dddk", "cUcsUsiUilUlbhfd", MergeNone, "aarch64_sve_extq", [], [ImmCheck<2, ImmCheckLaneIndex, 0>]>;
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SpencerAbson wrote:

[`extq` ](https://developer.arm.com/documentation/ddi0602/2024-09/SVE-Instructions/EXTQ--Extract-vector-segment-from-each-pair-of-quadword-vector-segments-?lang=en) differs from [`ext`](https://developer.arm.com/documentation/ddi0602/2024-09/SVE-Instructions/EXT--Extract-vector-from-pair-of-vectors-?lang=en) in that the immediate is relative to a single 128-bit vector segment, rather than the possibly 2048-bit vector.

We have `ImmCheckExtact` for `ext`:
>`def ImmCheckExtract             : ImmCheckType<2>;  // 0..(2048/sizeinbits(elt) - 1)`

But I believe we need to use `ImmCheckLaneIndex` here
> `def ImmCheckExtract             : ImmCheckType<2>;  // 0..(2048/sizeinbits(elt) - 1)`

https://github.com/llvm/llvm-project/pull/115340