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
@@ -10663,6 +10663,19 @@
     return DAG.getNode(ISD::ADD, DL, VT, Zext, DAG.getAllOnesConstant(DL, VT));
   }
 
+  // fold sext (not i1 X) -> add (zext i1 X), -1
+  // TODO: This could be extended to handle bool vectors.
+  if (N0.getValueType() == MVT::i1 && isBitwiseNot(N0) && N0.hasOneUse() &&
+      (!LegalOperations || (TLI.isOperationLegal(ISD::ZERO_EXTEND, VT) &&
+                            TLI.isOperationLegal(ISD::ADD, VT)))) {
+    // If we can eliminate the 'not', the sext form should be better
+    if (SDValue NewXor = visitXOR(N0.getNode()))
+      return DAG.getNode(ISD::SIGN_EXTEND, DL, VT, NewXor);
+
+    SDValue Zext = DAG.getNode(ISD::ZERO_EXTEND, DL, VT, N0.getOperand(0));
+    return DAG.getNode(ISD::ADD, DL, VT, Zext, DAG.getAllOnesConstant(DL, VT));
+  }
+
   return SDValue();
 }
 
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -46882,7 +46882,6 @@
                            const X86Subtarget &Subtarget) {
   SDValue N0 = N->getOperand(0);
   EVT VT = N->getValueType(0);
-  EVT InVT = N0.getValueType();
   SDLoc DL(N);
 
   // (i32 (sext (i8 (x86isd::setcc_carry)))) -> (i32 (x86isd::setcc_carry))
@@ -46911,16 +46910,6 @@
   if (SDValue V = combineExtSetcc(N, DAG, Subtarget))
     return V;
 
-  if (InVT == MVT::i1 && N0.getOpcode() == ISD::XOR &&
-      isAllOnesConstant(N0.getOperand(1)) && N0.hasOneUse()) {
-    // Invert and sign-extend a boolean is the same as zero-extend and subtract
-    // 1 because 0 becomes -1 and 1 becomes 0. The subtract is efficiently
-    // lowered with an LEA or a DEC. This is the same as: select Bool, 0, -1.
-    // sext (xor Bool, -1) --> sub (zext Bool), 1
-    SDValue Zext = DAG.getNode(ISD::ZERO_EXTEND, DL, VT, N0.getOperand(0));
-    return DAG.getNode(ISD::SUB, DL, VT, Zext, DAG.getConstant(1, DL, VT));
-  }
-
   if (SDValue V = combineToExtendBoolVectorInReg(N, DAG, DCI, Subtarget))
     return V;
 
diff --git a/llvm/test/CodeGen/AArch64/select_const.ll b/llvm/test/CodeGen/AArch64/select_const.ll
--- a/llvm/test/CodeGen/AArch64/select_const.ll
+++ b/llvm/test/CodeGen/AArch64/select_const.ll
@@ -68,8 +68,8 @@
 define i32 @select_0_or_neg1(i1 %cond) {
 ; CHECK-LABEL: select_0_or_neg1:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    mvn w8, w0
-; CHECK-NEXT:    sbfx w0, w8, #0, #1
+; CHECK-NEXT:    and w8, w0, #0x1
+; CHECK-NEXT:    sub w0, w8, #1 // =1
 ; CHECK-NEXT:    ret
   %sel = select i1 %cond, i32 0, i32 -1
   ret i32 %sel
@@ -78,8 +78,7 @@
 define i32 @select_0_or_neg1_zeroext(i1 zeroext %cond) {
 ; CHECK-LABEL: select_0_or_neg1_zeroext:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    mvn w8, w0
-; CHECK-NEXT:    sbfx w0, w8, #0, #1
+; CHECK-NEXT:    sub w0, w0, #1 // =1
 ; CHECK-NEXT:    ret
   %sel = select i1 %cond, i32 0, i32 -1
   ret i32 %sel
diff --git a/llvm/test/CodeGen/ARM/select_const.ll b/llvm/test/CodeGen/ARM/select_const.ll
--- a/llvm/test/CodeGen/ARM/select_const.ll
+++ b/llvm/test/CodeGen/ARM/select_const.ll
@@ -137,23 +137,21 @@
 define i32 @select_0_or_neg1(i1 %cond) {
 ; ARM-LABEL: select_0_or_neg1:
 ; ARM:       @ %bb.0:
-; ARM-NEXT:    mov r1, #1
-; ARM-NEXT:    bic r0, r1, r0
-; ARM-NEXT:    rsb r0, r0, #0
+; ARM-NEXT:    and r0, r0, #1
+; ARM-NEXT:    sub r0, r0, #1
 ; ARM-NEXT:    mov pc, lr
 ;
 ; THUMB2-LABEL: select_0_or_neg1:
 ; THUMB2:       @ %bb.0:
-; THUMB2-NEXT:    movs r1, #1
-; THUMB2-NEXT:    bic.w r0, r1, r0
-; THUMB2-NEXT:    rsbs r0, r0, #0
+; THUMB2-NEXT:    and r0, r0, #1
+; THUMB2-NEXT:    subs r0, #1
 ; THUMB2-NEXT:    bx lr
 ;
 ; THUMB-LABEL: select_0_or_neg1:
 ; THUMB:       @ %bb.0:
 ; THUMB-NEXT:    movs r1, #1
-; THUMB-NEXT:    bics r1, r0
-; THUMB-NEXT:    rsbs r0, r1, #0
+; THUMB-NEXT:    ands r1, r0
+; THUMB-NEXT:    subs r0, r1, #1
 ; THUMB-NEXT:    bx lr
   %sel = select i1 %cond, i32 0, i32 -1
   ret i32 %sel
@@ -162,21 +160,17 @@
 define i32 @select_0_or_neg1_zeroext(i1 zeroext %cond) {
 ; ARM-LABEL: select_0_or_neg1_zeroext:
 ; ARM:       @ %bb.0:
-; ARM-NEXT:    eor r0, r0, #1
-; ARM-NEXT:    rsb r0, r0, #0
+; ARM-NEXT:    sub r0, r0, #1
 ; ARM-NEXT:    mov pc, lr
 ;
 ; THUMB2-LABEL: select_0_or_neg1_zeroext:
 ; THUMB2:       @ %bb.0:
-; THUMB2-NEXT:    eor r0, r0, #1
-; THUMB2-NEXT:    rsbs r0, r0, #0
+; THUMB2-NEXT:    subs r0, #1
 ; THUMB2-NEXT:    bx lr
 ;
 ; THUMB-LABEL: select_0_or_neg1_zeroext:
 ; THUMB:       @ %bb.0:
-; THUMB-NEXT:    movs r1, #1
-; THUMB-NEXT:    eors r1, r0
-; THUMB-NEXT:    rsbs r0, r1, #0
+; THUMB-NEXT:    subs r0, r0, #1
 ; THUMB-NEXT:    bx lr
   %sel = select i1 %cond, i32 0, i32 -1
   ret i32 %sel
diff --git a/llvm/test/CodeGen/PowerPC/select_const.ll b/llvm/test/CodeGen/PowerPC/select_const.ll
--- a/llvm/test/CodeGen/PowerPC/select_const.ll
+++ b/llvm/test/CodeGen/PowerPC/select_const.ll
@@ -69,9 +69,8 @@
 define i32 @select_0_or_neg1(i1 %cond) {
 ; ALL-LABEL: select_0_or_neg1:
 ; ALL:       # %bb.0:
-; ALL-NEXT:    not 3, 3
 ; ALL-NEXT:    clrldi 3, 3, 63
-; ALL-NEXT:    neg 3, 3
+; ALL-NEXT:    addi 3, 3, -1
 ; ALL-NEXT:    blr
   %sel = select i1 %cond, i32 0, i32 -1
   ret i32 %sel
@@ -80,8 +79,7 @@
 define i32 @select_0_or_neg1_zeroext(i1 zeroext %cond) {
 ; ALL-LABEL: select_0_or_neg1_zeroext:
 ; ALL:       # %bb.0:
-; ALL-NEXT:    xori 3, 3, 1
-; ALL-NEXT:    neg 3, 3
+; ALL-NEXT:    addi 3, 3, -1
 ; ALL-NEXT:    blr
   %sel = select i1 %cond, i32 0, i32 -1
   ret i32 %sel
diff --git a/llvm/test/CodeGen/RISCV/sext-zext-trunc.ll b/llvm/test/CodeGen/RISCV/sext-zext-trunc.ll
--- a/llvm/test/CodeGen/RISCV/sext-zext-trunc.ll
+++ b/llvm/test/CodeGen/RISCV/sext-zext-trunc.ll
@@ -437,20 +437,18 @@
   ret i32 %1
 }
 
-;; TODO: fold (sext (not x)) -> (add (zext x) -1)
+;; fold (sext (not x)) -> (add (zext x) -1)
 define i32 @sext_of_not_i32(i1 %x) {
 ; RV32I-LABEL: sext_of_not_i32:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    not a0, a0
 ; RV32I-NEXT:    andi a0, a0, 1
-; RV32I-NEXT:    neg a0, a0
+; RV32I-NEXT:    addi a0, a0, -1
 ; RV32I-NEXT:    ret
 ;
 ; RV64I-LABEL: sext_of_not_i32:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    not a0, a0
 ; RV64I-NEXT:    andi a0, a0, 1
-; RV64I-NEXT:    neg a0, a0
+; RV64I-NEXT:    addi a0, a0, -1
 ; RV64I-NEXT:    ret
   %xor = xor i1 %x, 1
   %sext = sext i1 %xor to i32
@@ -460,24 +458,23 @@
 define i64 @sext_of_not_i64(i1 %x) {
 ; RV32I-LABEL: sext_of_not_i64:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    not a0, a0
-; RV32I-NEXT:    andi a0, a0, 1
-; RV32I-NEXT:    neg a0, a0
-; RV32I-NEXT:    mv a1, a0
+; RV32I-NEXT:    andi a1, a0, 1
+; RV32I-NEXT:    addi a0, a1, -1
+; RV32I-NEXT:    sltu a1, a0, a1
+; RV32I-NEXT:    addi a1, a1, -1
 ; RV32I-NEXT:    ret
 ;
 ; RV64I-LABEL: sext_of_not_i64:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    not a0, a0
 ; RV64I-NEXT:    andi a0, a0, 1
-; RV64I-NEXT:    neg a0, a0
+; RV64I-NEXT:    addi a0, a0, -1
 ; RV64I-NEXT:    ret
   %xor = xor i1 %x, 1
   %sext = sext i1 %xor to i64
   ret i64 %sext
 }
 
-;; TODO: fold (sext (not (setcc a, b, cc))) -> (sext (setcc a, b, !cc))
+;; fold (sext (not (setcc a, b, cc))) -> (sext (setcc a, b, !cc))
 define i32 @sext_of_not_cmp_i32(i32 %x) {
 ; RV32I-LABEL: sext_of_not_cmp_i32:
 ; RV32I:       # %bb.0:
diff --git a/llvm/test/CodeGen/SystemZ/sext-zext.ll b/llvm/test/CodeGen/SystemZ/sext-zext.ll
--- a/llvm/test/CodeGen/SystemZ/sext-zext.ll
+++ b/llvm/test/CodeGen/SystemZ/sext-zext.ll
@@ -1,20 +1,19 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
 
-;; TODO: fold (sext (not x)) -> (add (zext x) -1)
+;; fold (sext (not x)) -> (add (zext x) -1)
 define i32 @sext_of_not(i1 %x) {
 ; CHECK-LABEL: sext_of_not:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    xilf %r2, 4294967295
 ; CHECK-NEXT:    nilf %r2, 1
-; CHECK-NEXT:    lcr %r2, %r2
+; CHECK-NEXT:    ahi %r2, -1
 ; CHECK-NEXT:    br %r14
   %xor = xor i1 %x, 1
   %sext = sext i1 %xor to i32
   ret i32 %sext
 }
 
-;; TODO: fold (sext (not (setcc a, b, cc))) -> (sext (setcc a, b, !cc))
+;; fold (sext (not (setcc a, b, cc))) -> (sext (setcc a, b, !cc))
 define i32 @sext_of_not_cmp(i32 %x) {
 ; CHECK-LABEL: sext_of_not_cmp:
 ; CHECK:       # %bb.0:
diff --git a/llvm/test/CodeGen/X86/pr44140.ll b/llvm/test/CodeGen/X86/pr44140.ll
--- a/llvm/test/CodeGen/X86/pr44140.ll
+++ b/llvm/test/CodeGen/X86/pr44140.ll
@@ -49,8 +49,8 @@
 ; CHECK-NEXT:    movabsq $1010101010101010101, %rcx # imm = 0xE04998456557EB5
 ; CHECK-NEXT:    xorl %eax, %eax
 ; CHECK-NEXT:    cmpq %rcx, {{[0-9]+}}(%rsp)
-; CHECK-NEXT:    sete %al
-; CHECK-NEXT:    decl %eax
+; CHECK-NEXT:    setne %al
+; CHECK-NEXT:    negl %eax
 ; CHECK-NEXT:    addq $584, %rsp # imm = 0x248
 ; CHECK-NEXT:    .cfi_def_cfa_offset 8
 ; CHECK-NEXT:    retq