diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -3995,17 +3995,35 @@
   // so we are not afraid that we might mess up BZHI/BEXTR pattern.
 
   SDValue NewShiftAmt;
-  if (ShiftAmt->getOpcode() == ISD::ADD || ShiftAmt->getOpcode() == ISD::SUB) {
+  if (ShiftAmt->getOpcode() == ISD::ADD || ShiftAmt->getOpcode() == ISD::SUB ||
+      ShiftAmt->getOpcode() == ISD::XOR) {
     SDValue Add0 = ShiftAmt->getOperand(0);
     SDValue Add1 = ShiftAmt->getOperand(1);
     auto *Add0C = dyn_cast<ConstantSDNode>(Add0);
     auto *Add1C = dyn_cast<ConstantSDNode>(Add1);
-    // If we are shifting by X+/-N where N == 0 mod Size, then just shift by X
-    // to avoid the ADD/SUB.
+    // If we are shifting by X+/-/^N where N == 0 mod Size, then just shift by X
+    // to avoid the ADD/SUB/XOR.
     if (Add1C && Add1C->getAPIntValue().urem(Size) == 0) {
       NewShiftAmt = Add0;
-      // If we are shifting by N-X where N == 0 mod Size, then just shift by -X
-      // to generate a NEG instead of a SUB of a constant.
+
+    } else if ((Add0C && Add0C->getAPIntValue().urem(Size) == Size - 1) ||
+               (Add1C && Add1C->getAPIntValue().urem(Size) == Size - 1)) {
+      // If we are doing a NOT on just the lower bits with (Size*N-1) -/^ X
+      // we can replace it with a NOT. In the XOR case it may save some code
+      // size, in the SUB case it also may save a move.
+      assert(Add0C == nullptr || Add1C == nullptr);
+
+      auto *ConstValOp = Add0C == nullptr ? Add1C : Add0C;
+      EVT OpVT = ShiftAmt.getValueType();
+      // ISelLowering will convert this to NOT already.
+      if (ConstValOp->isAllOnes())
+        return false;
+
+      NewShiftAmt = CurDAG->getNOT(DL, Add0C == nullptr ? Add0 : Add1, OpVT);
+
+      insertDAGNode(*CurDAG, OrigShiftAmt, NewShiftAmt);
+      // If we are shifting by N-X where N == 0 mod Size, then just shift by
+      // -X to generate a NEG instead of a SUB of a constant.
     } else if (ShiftAmt->getOpcode() == ISD::SUB && Add0C &&
                Add0C->getZExtValue() != 0) {
       EVT SubVT = ShiftAmt.getValueType();
diff --git a/llvm/test/CodeGen/X86/legalize-shift-64.ll b/llvm/test/CodeGen/X86/legalize-shift-64.ll
--- a/llvm/test/CodeGen/X86/legalize-shift-64.ll
+++ b/llvm/test/CodeGen/X86/legalize-shift-64.ll
@@ -10,7 +10,7 @@
 ; CHECK-NEXT:    movl %edx, %eax
 ; CHECK-NEXT:    shll %cl, %eax
 ; CHECK-NEXT:    shrl %edx
-; CHECK-NEXT:    xorb $31, %cl
+; CHECK-NEXT:    notb %cl
 ; CHECK-NEXT:    shrl %cl, %edx
 ; CHECK-NEXT:    retl
   %conv = zext i32 %xx to i64
diff --git a/llvm/test/CodeGen/X86/not-shift.ll b/llvm/test/CodeGen/X86/not-shift.ll
--- a/llvm/test/CodeGen/X86/not-shift.ll
+++ b/llvm/test/CodeGen/X86/not-shift.ll
@@ -50,17 +50,17 @@
 ;
 ; X64-NOBMI2-LABEL: sub63_shiftl64:
 ; X64-NOBMI2:       # %bb.0:
+; X64-NOBMI2-NEXT:    movq %rsi, %rcx
 ; X64-NOBMI2-NEXT:    movq %rdi, %rax
-; X64-NOBMI2-NEXT:    movb $63, %cl
-; X64-NOBMI2-NEXT:    subb %sil, %cl
+; X64-NOBMI2-NEXT:    notb %cl
+; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $rcx
 ; X64-NOBMI2-NEXT:    shlq %cl, %rax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: sub63_shiftl64:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    movb $63, %al
-; X64-BMI2-NEXT:    subb %sil, %al
-; X64-BMI2-NEXT:    shlxq %rax, %rdi, %rax
+; X64-BMI2-NEXT:    notb %sil
+; X64-BMI2-NEXT:    shlxq %rsi, %rdi, %rax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = sub i64 63, %cnt
   %result = shl i64 %val, %adjcnt
@@ -107,14 +107,14 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movq %rsi, %rcx
 ; X64-NOBMI2-NEXT:    movq %rdi, %rax
-; X64-NOBMI2-NEXT:    xorb $63, %cl
+; X64-NOBMI2-NEXT:    notb %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $rcx
 ; X64-NOBMI2-NEXT:    shrq %cl, %rax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: xor63_shiftr64:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $63, %sil
+; X64-BMI2-NEXT:    notb %sil
 ; X64-BMI2-NEXT:    shrxq %rsi, %rdi, %rax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = xor i64 %cnt, 63
@@ -162,14 +162,14 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movq %rsi, %rcx
 ; X64-NOBMI2-NEXT:    movq %rdi, %rax
-; X64-NOBMI2-NEXT:    xorb $127, %cl
+; X64-NOBMI2-NEXT:    notb %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $rcx
 ; X64-NOBMI2-NEXT:    shlq %cl, %rax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: sub127_shiftl64:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $127, %sil
+; X64-BMI2-NEXT:    notb %sil
 ; X64-BMI2-NEXT:    shlxq %rsi, %rdi, %rax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = sub i64 127, %cnt
@@ -217,14 +217,14 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movq %rsi, %rcx
 ; X64-NOBMI2-NEXT:    movq %rdi, %rax
-; X64-NOBMI2-NEXT:    xorb $127, %cl
+; X64-NOBMI2-NEXT:    notb %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $rcx
 ; X64-NOBMI2-NEXT:    shrq %cl, %rax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: xor127_shiftr64:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $127, %sil
+; X64-BMI2-NEXT:    notb %sil
 ; X64-BMI2-NEXT:    shrxq %rsi, %rdi, %rax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = xor i64 %cnt, 127
@@ -272,14 +272,12 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movq %rsi, %rcx
 ; X64-NOBMI2-NEXT:    movq %rdi, %rax
-; X64-NOBMI2-NEXT:    xorb $64, %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $rcx
 ; X64-NOBMI2-NEXT:    shlq %cl, %rax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: xor64_shiftl64:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $64, %sil
 ; X64-BMI2-NEXT:    shlxq %rsi, %rdi, %rax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = xor i64 %cnt, 64
@@ -401,31 +399,31 @@
 ; X86-NOBMI2-LABEL: sub31_shiftr32:
 ; X86-NOBMI2:       # %bb.0:
 ; X86-NOBMI2-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NOBMI2-NEXT:    movb $31, %cl
-; X86-NOBMI2-NEXT:    subb {{[0-9]+}}(%esp), %cl
+; X86-NOBMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
+; X86-NOBMI2-NEXT:    notb %cl
 ; X86-NOBMI2-NEXT:    shrl %cl, %eax
 ; X86-NOBMI2-NEXT:    retl
 ;
 ; X86-BMI2-LABEL: sub31_shiftr32:
 ; X86-BMI2:       # %bb.0:
-; X86-BMI2-NEXT:    movb $31, %al
-; X86-BMI2-NEXT:    subb {{[0-9]+}}(%esp), %al
+; X86-BMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
+; X86-BMI2-NEXT:    notb %al
 ; X86-BMI2-NEXT:    shrxl %eax, {{[0-9]+}}(%esp), %eax
 ; X86-BMI2-NEXT:    retl
 ;
 ; X64-NOBMI2-LABEL: sub31_shiftr32:
 ; X64-NOBMI2:       # %bb.0:
+; X64-NOBMI2-NEXT:    movl %esi, %ecx
 ; X64-NOBMI2-NEXT:    movl %edi, %eax
-; X64-NOBMI2-NEXT:    movb $31, %cl
-; X64-NOBMI2-NEXT:    subb %sil, %cl
+; X64-NOBMI2-NEXT:    notb %cl
+; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $ecx
 ; X64-NOBMI2-NEXT:    shrl %cl, %eax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: sub31_shiftr32:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    movb $31, %al
-; X64-BMI2-NEXT:    subb %sil, %al
-; X64-BMI2-NEXT:    shrxl %eax, %edi, %eax
+; X64-BMI2-NEXT:    notb %sil
+; X64-BMI2-NEXT:    shrxl %esi, %edi, %eax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = sub i32 31, %cnt
   %result = lshr i32 %val, %adjcnt
@@ -437,14 +435,14 @@
 ; X86-NOBMI2:       # %bb.0:
 ; X86-NOBMI2-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NOBMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
-; X86-NOBMI2-NEXT:    xorb $31, %cl
+; X86-NOBMI2-NEXT:    notb %cl
 ; X86-NOBMI2-NEXT:    shll %cl, %eax
 ; X86-NOBMI2-NEXT:    retl
 ;
 ; X86-BMI2-LABEL: xor31_shiftl32:
 ; X86-BMI2:       # %bb.0:
 ; X86-BMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
-; X86-BMI2-NEXT:    xorb $31, %al
+; X86-BMI2-NEXT:    notb %al
 ; X86-BMI2-NEXT:    shlxl %eax, {{[0-9]+}}(%esp), %eax
 ; X86-BMI2-NEXT:    retl
 ;
@@ -452,14 +450,14 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movl %esi, %ecx
 ; X64-NOBMI2-NEXT:    movl %edi, %eax
-; X64-NOBMI2-NEXT:    xorb $31, %cl
+; X64-NOBMI2-NEXT:    notb %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $ecx
 ; X64-NOBMI2-NEXT:    shll %cl, %eax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: xor31_shiftl32:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $31, %sil
+; X64-BMI2-NEXT:    notb %sil
 ; X64-BMI2-NEXT:    shlxl %esi, %edi, %eax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = xor i32 %cnt, 31
@@ -471,31 +469,31 @@
 ; X86-NOBMI2-LABEL: sub63_shiftr32:
 ; X86-NOBMI2:       # %bb.0:
 ; X86-NOBMI2-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NOBMI2-NEXT:    movb $63, %cl
-; X86-NOBMI2-NEXT:    subb {{[0-9]+}}(%esp), %cl
+; X86-NOBMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
+; X86-NOBMI2-NEXT:    notb %cl
 ; X86-NOBMI2-NEXT:    shrl %cl, %eax
 ; X86-NOBMI2-NEXT:    retl
 ;
 ; X86-BMI2-LABEL: sub63_shiftr32:
 ; X86-BMI2:       # %bb.0:
-; X86-BMI2-NEXT:    movb $63, %al
-; X86-BMI2-NEXT:    subb {{[0-9]+}}(%esp), %al
+; X86-BMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
+; X86-BMI2-NEXT:    notb %al
 ; X86-BMI2-NEXT:    shrxl %eax, {{[0-9]+}}(%esp), %eax
 ; X86-BMI2-NEXT:    retl
 ;
 ; X64-NOBMI2-LABEL: sub63_shiftr32:
 ; X64-NOBMI2:       # %bb.0:
+; X64-NOBMI2-NEXT:    movl %esi, %ecx
 ; X64-NOBMI2-NEXT:    movl %edi, %eax
-; X64-NOBMI2-NEXT:    movb $63, %cl
-; X64-NOBMI2-NEXT:    subb %sil, %cl
+; X64-NOBMI2-NEXT:    notb %cl
+; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $ecx
 ; X64-NOBMI2-NEXT:    shrl %cl, %eax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: sub63_shiftr32:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    movb $63, %al
-; X64-BMI2-NEXT:    subb %sil, %al
-; X64-BMI2-NEXT:    shrxl %eax, %edi, %eax
+; X64-BMI2-NEXT:    notb %sil
+; X64-BMI2-NEXT:    shrxl %esi, %edi, %eax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = sub i32 63, %cnt
   %result = lshr i32 %val, %adjcnt
@@ -507,14 +505,14 @@
 ; X86-NOBMI2:       # %bb.0:
 ; X86-NOBMI2-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NOBMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
-; X86-NOBMI2-NEXT:    xorb $63, %cl
+; X86-NOBMI2-NEXT:    notb %cl
 ; X86-NOBMI2-NEXT:    shll %cl, %eax
 ; X86-NOBMI2-NEXT:    retl
 ;
 ; X86-BMI2-LABEL: xor63_shiftl32:
 ; X86-BMI2:       # %bb.0:
 ; X86-BMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
-; X86-BMI2-NEXT:    xorb $63, %al
+; X86-BMI2-NEXT:    notb %al
 ; X86-BMI2-NEXT:    shlxl %eax, {{[0-9]+}}(%esp), %eax
 ; X86-BMI2-NEXT:    retl
 ;
@@ -522,14 +520,14 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movl %esi, %ecx
 ; X64-NOBMI2-NEXT:    movl %edi, %eax
-; X64-NOBMI2-NEXT:    xorb $63, %cl
+; X64-NOBMI2-NEXT:    notb %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $ecx
 ; X64-NOBMI2-NEXT:    shll %cl, %eax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: xor63_shiftl32:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $63, %sil
+; X64-BMI2-NEXT:    notb %sil
 ; X64-BMI2-NEXT:    shlxl %esi, %edi, %eax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = xor i32 %cnt, 63
@@ -540,16 +538,14 @@
 define i32 @xor32_shiftr32(i32 %val, i32 %cnt) nounwind {
 ; X86-NOBMI2-LABEL: xor32_shiftr32:
 ; X86-NOBMI2:       # %bb.0:
-; X86-NOBMI2-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NOBMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
-; X86-NOBMI2-NEXT:    xorb $32, %cl
+; X86-NOBMI2-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NOBMI2-NEXT:    shrl %cl, %eax
 ; X86-NOBMI2-NEXT:    retl
 ;
 ; X86-BMI2-LABEL: xor32_shiftr32:
 ; X86-BMI2:       # %bb.0:
 ; X86-BMI2-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
-; X86-BMI2-NEXT:    xorb $32, %al
 ; X86-BMI2-NEXT:    shrxl %eax, {{[0-9]+}}(%esp), %eax
 ; X86-BMI2-NEXT:    retl
 ;
@@ -557,14 +553,12 @@
 ; X64-NOBMI2:       # %bb.0:
 ; X64-NOBMI2-NEXT:    movl %esi, %ecx
 ; X64-NOBMI2-NEXT:    movl %edi, %eax
-; X64-NOBMI2-NEXT:    xorb $32, %cl
 ; X64-NOBMI2-NEXT:    # kill: def $cl killed $cl killed $ecx
 ; X64-NOBMI2-NEXT:    shrl %cl, %eax
 ; X64-NOBMI2-NEXT:    retq
 ;
 ; X64-BMI2-LABEL: xor32_shiftr32:
 ; X64-BMI2:       # %bb.0:
-; X64-BMI2-NEXT:    xorb $32, %sil
 ; X64-BMI2-NEXT:    shrxl %esi, %edi, %eax
 ; X64-BMI2-NEXT:    retq
   %adjcnt = xor i32 %cnt, 32