diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 3f780285efe42..be2f2fdd66997 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -4213,22 +4213,36 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
     });
     SimplifyQuery Q = SQ.getWithInstruction(&SI).getWithCondContext(CC);
     if (!CC.AffectedValues.empty()) {
-      if (!isa<Constant>(TrueVal) &&
-          hasAffectedValue(TrueVal, CC.AffectedValues, /*Depth=*/0)) {
-        KnownBits Known = llvm::computeKnownBits(TrueVal, /*Depth=*/0, Q);
-        if (Known.isConstant())
-          return replaceOperand(SI, 1,
-                                ConstantInt::get(SelType, Known.getConstant()));
-      }
+      std::optional<bool> NotUndef;
+      auto SimplifyOp = [&](unsigned OpNum) -> Instruction * {
+        Value *V = SI.getOperand(OpNum);
+        if (isa<Constant>(V) ||
+            !hasAffectedValue(V, CC.AffectedValues, /*Depth=*/0))
+          return nullptr;
+
+        if (!NotUndef)
+          NotUndef = isGuaranteedNotToBeUndef(CondVal);
 
+        if (*NotUndef) {
+          unsigned BitWidth = SelType->getScalarSizeInBits();
+          KnownBits Known(BitWidth);
+          if (SimplifyDemandedBits(&SI, OpNum, APInt::getAllOnes(BitWidth),
+                                   Known, /*Depth=*/0, Q))
+            return &SI;
+        } else {
+          KnownBits Known = llvm::computeKnownBits(V, /*Depth=*/0, Q);
+          if (Known.isConstant())
+            return replaceOperand(
+                SI, OpNum, ConstantInt::get(SelType, Known.getConstant()));
+        }
+        return nullptr;
+      };
+
+      if (Instruction *Res = SimplifyOp(1))
+        return Res;
       CC.Invert = true;
-      if (!isa<Constant>(FalseVal) &&
-          hasAffectedValue(FalseVal, CC.AffectedValues, /*Depth=*/0)) {
-        KnownBits Known = llvm::computeKnownBits(FalseVal, /*Depth=*/0, Q);
-        if (Known.isConstant())
-          return replaceOperand(SI, 2,
-                                ConstantInt::get(SelType, Known.getConstant()));
-      }
+      if (Instruction *Res = SimplifyOp(2))
+        return Res;
     }
   }
 
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index ee6b60f7f70d6..29efd8462cb28 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -320,6 +320,7 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Instruction *I,
     // bits on that side are also known to be set on the other side, turn this
     // into an AND, as we know the bits will be cleared.
     //    e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
+#if 0
     if (DemandedMask.isSubsetOf(RHSKnown.Zero|RHSKnown.One) &&
         RHSKnown.One.isSubsetOf(LHSKnown.One)) {
       Constant *AndC = Constant::getIntegerValue(VTy,
@@ -327,6 +328,7 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Instruction *I,
       Instruction *And = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
       return InsertNewInstWith(And, I->getIterator());
     }
+#endif
 
     // If the RHS is a constant, see if we can change it. Don't alter a -1
     // constant because that's a canonical 'not' op, and that is better for
diff --git a/llvm/test/Transforms/InstCombine/add.ll b/llvm/test/Transforms/InstCombine/add.ll
index 417c3a950d780..12e55557d504a 100644
--- a/llvm/test/Transforms/InstCombine/add.ll
+++ b/llvm/test/Transforms/InstCombine/add.ll
@@ -1196,8 +1196,8 @@ define i32 @add_to_sub2(i32 %A, i32 %M) {
 ; (X | C1) + C2 --> (X | C1) ^ C1 iff (C1 == -C2)
 define i32 @test44(i32 %A) {
 ; CHECK-LABEL: @test44(
-; CHECK-NEXT:    [[C:%.*]] = and i32 [[A:%.*]], -124
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], -124
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %B = or i32 %A, 123
   %C = add i32 %B, -123
@@ -1207,7 +1207,7 @@ define i32 @test44(i32 %A) {
 define i32 @test44_extra_use(i32 %A) {
 ; CHECK-LABEL: @test44_extra_use(
 ; CHECK-NEXT:    [[B:%.*]] = or i32 [[A:%.*]], 123
-; CHECK-NEXT:    [[C:%.*]] = and i32 [[A]], -124
+; CHECK-NEXT:    [[C:%.*]] = xor i32 [[B]], 123
 ; CHECK-NEXT:    [[D:%.*]] = mul i32 [[B]], [[C]]
 ; CHECK-NEXT:    ret i32 [[D]]
 ;
@@ -1230,8 +1230,8 @@ define i32 @test44_non_matching(i32 %A) {
 
 define <2 x i32> @test44_vec(<2 x i32> %A) {
 ; CHECK-LABEL: @test44_vec(
-; CHECK-NEXT:    [[C:%.*]] = and <2 x i32> [[A:%.*]], <i32 -124, i32 -124>
-; CHECK-NEXT:    ret <2 x i32> [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[A:%.*]], <i32 -124, i32 -124>
+; CHECK-NEXT:    ret <2 x i32> [[TMP1]]
 ;
   %B = or <2 x i32> %A, <i32 123, i32 123>
   %C = add <2 x i32> %B, <i32 -123, i32 -123>
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 7d62b41942440..d66bab4c0b4e3 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -2989,9 +2989,8 @@ define i8 @select_replacement_loop3(i32 noundef %x) {
 
 define i16 @select_replacement_loop4(i16 noundef %p_12) {
 ; CHECK-LABEL: @select_replacement_loop4(
-; CHECK-NEXT:    [[AND1:%.*]] = and i16 [[P_12:%.*]], 1
-; CHECK-NEXT:    [[CMP21:%.*]] = icmp ult i16 [[P_12]], 2
-; CHECK-NEXT:    [[AND3:%.*]] = select i1 [[CMP21]], i16 [[AND1]], i16 0
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i16 [[P_12:%.*]], 2
+; CHECK-NEXT:    [[AND3:%.*]] = select i1 [[CMP1]], i16 [[P_12]], i16 0
 ; CHECK-NEXT:    ret i16 [[AND3]]
 ;
   %cmp1 = icmp ult i16 %p_12, 2
@@ -4671,8 +4670,7 @@ define i8 @select_knownbits_simplify(i8 noundef %x)  {
 ; CHECK-LABEL: @select_knownbits_simplify(
 ; CHECK-NEXT:    [[X_LO:%.*]] = and i8 [[X:%.*]], 1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[X_LO]], 0
-; CHECK-NEXT:    [[AND:%.*]] = and i8 [[X]], -2
-; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i8 [[AND]], i8 0
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i8 [[X]], i8 0
 ; CHECK-NEXT:    ret i8 [[RES]]
 ;
   %x.lo = and i8 %x, 1
@@ -4686,8 +4684,7 @@ define i8 @select_knownbits_simplify_nested(i8 noundef %x)  {
 ; CHECK-LABEL: @select_knownbits_simplify_nested(
 ; CHECK-NEXT:    [[X_LO:%.*]] = and i8 [[X:%.*]], 1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[X_LO]], 0
-; CHECK-NEXT:    [[AND:%.*]] = and i8 [[X]], -2
-; CHECK-NEXT:    [[MUL:%.*]] = mul i8 [[AND]], [[AND]]
+; CHECK-NEXT:    [[MUL:%.*]] = mul i8 [[X]], [[X]]
 ; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 0
 ; CHECK-NEXT:    ret i8 [[RES]]
 ;