[llvm] [VPlan] Extract reverse operation for reverse accesses (PR #146525)

[Mel Chen via llvm-commits]

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@@ -23,6 +23,7 @@ define void @lshift_significand(i32 %n, ptr nocapture writeonly %dst) {
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[N_RND_UP]], [[N_MOD_VF]]
 ; CHECK-NEXT:    [[TMP8:%.*]] = call i64 @llvm.vscale.i64()
 ; CHECK-NEXT:    [[TMP9:%.*]] = mul nuw i64 [[TMP8]], 2
+; CHECK-NEXT:    [[VP_REVERSE:%.*]] = call <vscale x 2 x i64> @llvm.vector.reverse.nxv2i64(<vscale x 2 x i64> zeroinitializer)
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Mel-Chen wrote:

Yes. But I think it's fine that this isn't converted into vp.reverse here, since the operand of reverse that can be hoisted by LICM should be uniform. We could even remove the reverse operation entirely in this case in the future.

https://github.com/llvm/llvm-project/pull/146525