diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7778,8 +7778,10 @@
 
   SDLoc DL(N);
 
-  // If Y is a constant, check that 'andn' works with immediates.
-  if (!TLI.hasAndNot(Y)) {
+  // If Y is a constant, check that 'andn' works with immediates. Unless M is
+  // a not that would already allow ANDN to be used.
+  // FIXME: If M is a not, do we need to check if X is a constant?
+  if (!TLI.hasAndNot(Y) && !isBitwiseNot(M)) {
     assert(TLI.hasAndNot(X) && "Only mask is a variable? Unreachable.");
     // If not, we need to do a bit more work to make sure andn is still used.
     SDValue NotX = DAG.getNOT(DL, X, VT);
diff --git a/llvm/test/CodeGen/X86/unfold-masked-merge-scalar-variablemask.ll b/llvm/test/CodeGen/X86/unfold-masked-merge-scalar-variablemask.ll
--- a/llvm/test/CodeGen/X86/unfold-masked-merge-scalar-variablemask.ll
+++ b/llvm/test/CodeGen/X86/unfold-masked-merge-scalar-variablemask.ll
@@ -705,10 +705,9 @@
 ;
 ; CHECK-BMI-LABEL: in_constant_varx_42_invmask:
 ; CHECK-BMI:       # %bb.0:
-; CHECK-BMI-NEXT:    notl %edx
-; CHECK-BMI-NEXT:    andnl %edx, %edi, %eax
-; CHECK-BMI-NEXT:    orl $42, %edx
-; CHECK-BMI-NEXT:    andnl %edx, %eax, %eax
+; CHECK-BMI-NEXT:    andnl %edi, %edx, %eax
+; CHECK-BMI-NEXT:    andl $42, %edx
+; CHECK-BMI-NEXT:    orl %edx, %eax
 ; CHECK-BMI-NEXT:    retq
   %notmask = xor i32 %mask, -1
   %n0 = xor i32 %x, 42 ; %x