[llvm] [LV] Remove IV use restrictions for epilogue vectorization. (PR #190552)

[David Sherwood via llvm-commits]

================
@@ -30,19 +33,38 @@ define i64 @penultimate_iv_live_out(ptr %dst, i64 %N) {
 ; CHECK:       [[MIDDLE_BLOCK]]:
 ; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 [[N]], [[N_VEC]]
 ; CHECK-NEXT:    [[IND_ESCAPE:%.*]] = sub i64 [[N_VEC]], 1
-; CHECK-NEXT:    br i1 [[CMP_N]], label %[[EXIT:.*]], label %[[SCALAR_PH]]
+; CHECK-NEXT:    br i1 [[CMP_N]], label %[[EXIT:.*]], label %[[VEC_EPILOG_ITER_CHECK:.*]]
+; CHECK:       [[VEC_EPILOG_ITER_CHECK]]:
+; CHECK-NEXT:    [[MIN_EPILOG_ITERS_CHECK:%.*]] = icmp ult i64 [[N_MOD_VF]], 4
+; CHECK-NEXT:    br i1 [[MIN_EPILOG_ITERS_CHECK]], label %[[VEC_EPILOG_SCALAR_PH]], label %[[SCALAR_PH]], !prof [[PROF3:![0-9]+]]
----------------
david-arm wrote:

Pretty sure that should be ``br i1 [[MIN_EPILOG_ITERS_CHECK]], label %[[SCALAR_PH]], label %[[VEC_EPILOG_SCALAR_PH]]``. :) Think the blocks are badly named

https://github.com/llvm/llvm-project/pull/190552