diff --git a/base/compiler/ssair/ir.jl b/base/compiler/ssair/ir.jl
index f4d7d468feba1..769e373bac286 100644
--- a/base/compiler/ssair/ir.jl
+++ b/base/compiler/ssair/ir.jl
@@ -950,6 +950,8 @@ end
 __set_check_ssa_counts(onoff::Bool) = __check_ssa_counts__[] = onoff
 const __check_ssa_counts__ = fill(false)
 
+should_check_ssa_counts() = __check_ssa_counts__[]
+
 function _oracle_check(compact::IncrementalCompact)
     observed_used_ssas = Core.Compiler.find_ssavalue_uses1(compact)
     for i = 1:length(observed_used_ssas)
@@ -1683,7 +1685,7 @@ end
 function complete(compact::IncrementalCompact)
     result_bbs = resize!(compact.result_bbs, compact.active_result_bb-1)
     cfg = CFG(result_bbs, Int[first(result_bbs[i].stmts) for i in 2:length(result_bbs)])
-    if __check_ssa_counts__[]
+    if should_check_ssa_counts()
         oracle_check(compact)
     end
 
diff --git a/base/compiler/ssair/passes.jl b/base/compiler/ssair/passes.jl
index 1d9417fb7ca7d..cf2d87f3bfdb2 100644
--- a/base/compiler/ssair/passes.jl
+++ b/base/compiler/ssair/passes.jl
@@ -1511,6 +1511,30 @@ function is_union_phi(compact::IncrementalCompact, idx::Int)
     return is_some_union(inst[:type])
 end
 
+function kill_phi!(compact::IncrementalCompact, phi_uses::Vector{Int},
+                    to_drop::Union{Vector{Int}, UnitRange{Int}},
+                    ssa::SSAValue, phi::PhiNode, delete_inst::Bool = false)
+    for d in to_drop
+        if isassigned(phi.values, d)
+            val = phi.values[d]
+            if !delete_inst
+                # Deleting the inst will update compact's use count, so
+                # don't do it here.
+                kill_current_use(compact, val)
+            end
+            if isa(val, SSAValue)
+                phi_uses[val.id] -= 1
+            end
+        end
+    end
+    if delete_inst
+        compact[ssa] = nothing
+    elseif !isempty(to_drop)
+        deleteat!(phi.values, to_drop)
+        deleteat!(phi.edges, to_drop)
+    end
+end
+
 """
     adce_pass!(ir::IRCode) -> newir::IRCode
 
@@ -1596,7 +1620,8 @@ function adce_pass!(ir::IRCode)
         phi = unionphi[1]
         t = unionphi[2]
         if t === Union{}
-            compact[SSAValue(phi)] = nothing
+            stmt = compact[SSAValue(phi)][:inst]::PhiNode
+            kill_phi!(compact, phi_uses, 1:length(stmt.values), SSAValue(phi), stmt, true)
             continue
         elseif t === Any
             continue
@@ -1617,12 +1642,7 @@ function adce_pass!(ir::IRCode)
             end
         end
         compact.result[phi][:type] = t
-        isempty(to_drop) && continue
-        for d in to_drop
-            isassigned(stmt.values, d) && kill_current_use(compact, stmt.values[d])
-        end
-        deleteat!(stmt.values, to_drop)
-        deleteat!(stmt.edges, to_drop)
+        kill_phi!(compact, phi_uses, to_drop, SSAValue(phi), stmt, false)
     end
     # Perform simple DCE for unused values
     extra_worklist = Int[]
diff --git a/test/compiler/irpasses.jl b/test/compiler/irpasses.jl
index a85a8a80f288f..ec26cab55da14 100644
--- a/test/compiler/irpasses.jl
+++ b/test/compiler/irpasses.jl
@@ -1092,3 +1092,13 @@ let src = code_typed1(foo_defined_last_iter, Tuple{Int})
         end
     end
 end
+
+# Issue #47180, incorrect phi counts in CmdRedirect
+function a47180(b; stdout )
+    c = setenv(b, b.env)
+    if true
+        c = pipeline(c, stdout)
+    end
+    c
+end
+@test isa(a47180(``; stdout), Base.AbstractCmd)