diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -277,6 +277,10 @@
     ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0);
 
   BinaryOperator *Res = CreateMul(Neg->getOperand(OpNo), NegOne, "", Neg, Neg);
+  if (OverflowingBinaryOperator *OBON = dyn_cast<OverflowingBinaryOperator>(Neg)) {
+    Res->setHasNoSignedWrap(OBON->hasNoSignedWrap());
+    Res->setHasNoUnsignedWrap(OBON->hasNoUnsignedWrap());
+  }
   Neg->setOperand(OpNo, Constant::getNullValue(Ty)); // Drop use of op.
   Res->takeName(Neg);
   Neg->replaceAllUsesWith(Res);
@@ -787,8 +791,17 @@
         FastMathFlags Flags = I->getFastMathFlags();
         ExpressionChanged->clearSubclassOptionalData();
         ExpressionChanged->setFastMathFlags(Flags);
-      } else
+      } else {
+        // Preserve nsw/nuw flags.
+        OverflowingBinaryOperator *OBOI = dyn_cast<OverflowingBinaryOperator>(I);
+        bool NSW = OBOI ? OBOI->hasNoSignedWrap() : false;
+        bool NUW = OBOI ? OBOI->hasNoUnsignedWrap() : false;
         ExpressionChanged->clearSubclassOptionalData();
+        if (isa<OverflowingBinaryOperator>(ExpressionChanged)) {
+          ExpressionChanged->setHasNoSignedWrap(NSW);
+          ExpressionChanged->setHasNoUnsignedWrap(NUW);
+        }
+      }
 
       if (ExpressionChanged == I)
         break;
@@ -1062,6 +1075,10 @@
   // Everyone now refers to the add instruction.
   Sub->replaceAllUsesWith(New);
   New->setDebugLoc(Sub->getDebugLoc());
+  if (OverflowingBinaryOperator *OBOS = dyn_cast<OverflowingBinaryOperator>(Sub)) {
+    New->setHasNoSignedWrap(OBOS->hasNoSignedWrap());
+    New->setHasNoUnsignedWrap(OBOS->hasNoUnsignedWrap());
+  }
 
   LLVM_DEBUG(dbgs() << "Negated: " << *New << '\n');
   return New;
@@ -1953,6 +1970,10 @@
 
   if (Ops.size() == 1) return Ops[0].Op;
 
+  OverflowingBinaryOperator *OBOI = dyn_cast<OverflowingBinaryOperator>(I);
+  bool NSW = OBOI ? OBOI->hasNoSignedWrap() : false;
+  bool NUW = OBOI ? OBOI->hasNoUnsignedWrap() : false;
+
   // Handle destructive annihilation due to identities between elements in the
   // argument list here.
   unsigned NumOps = Ops.size();
@@ -1971,14 +1992,26 @@
 
   case Instruction::Add:
   case Instruction::FAdd:
-    if (Value *Result = OptimizeAdd(I, Ops))
+    if (Value *Result = OptimizeAdd(I, Ops)) {
+      BinaryOperator *BO = dyn_cast<BinaryOperator>(Result);
+      if (isa_and_nonnull<OverflowingBinaryOperator>(BO)) {
+        BO->setHasNoSignedWrap(NSW);
+        BO->setHasNoUnsignedWrap(NUW);
+      }
       return Result;
+    }
     break;
 
   case Instruction::Mul:
   case Instruction::FMul:
-    if (Value *Result = OptimizeMul(I, Ops))
+    if (Value *Result = OptimizeMul(I, Ops)) {
+      BinaryOperator *BO = dyn_cast<BinaryOperator>(Result);
+      if (isa_and_nonnull<OverflowingBinaryOperator>(BO)) {
+        BO->setHasNoSignedWrap(NSW);
+        BO->setHasNoUnsignedWrap(NUW);
+      }
       return Result;
+    }
     break;
   }
 
diff --git a/llvm/test/Transforms/Reassociate/cse-pairs.ll b/llvm/test/Transforms/Reassociate/cse-pairs.ll
--- a/llvm/test/Transforms/Reassociate/cse-pairs.ll
+++ b/llvm/test/Transforms/Reassociate/cse-pairs.ll
@@ -32,9 +32,9 @@
 
 define signext i32 @twoPairsAllOpInPairs(i32 signext %0, i32 signext %1, i32 signext %2, i32 signext %3) {
 ; CHECK-LABEL: @twoPairsAllOpInPairs(
-; CHECK-NEXT:    [[TMP5:%.*]] = add i32 [[TMP2:%.*]], [[TMP1:%.*]]
-; CHECK-NEXT:    [[TMP6:%.*]] = add i32 [[TMP5]], [[TMP0:%.*]]
-; CHECK-NEXT:    [[TMP7:%.*]] = add i32 [[TMP6]], [[TMP3:%.*]]
+; CHECK-NEXT:    [[TMP5:%.*]] = add nsw i32 [[TMP2:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT:    [[TMP6:%.*]] = add nsw i32 [[TMP5]], [[TMP0:%.*]]
+; CHECK-NEXT:    [[TMP7:%.*]] = add nsw i32 [[TMP6]], [[TMP3:%.*]]
 ; CHECK-NEXT:    store i32 [[TMP7]], i32* @num1, align 4
 ; CHECK-NEXT:    store i32 [[TMP5]], i32* @num2, align 4
 ; CHECK-NEXT:    [[TMP8:%.*]] = add nsw i32 [[TMP3]], [[TMP0]]
@@ -54,11 +54,11 @@
 
 define signext i32 @threePairsAllOpInPairs(i32 signext %0, i32 signext %1, i32 signext %2, i32 signext %3, i32 signext %4, i32 signext %5) {
 ; CHECK-LABEL: @threePairsAllOpInPairs(
-; CHECK-NEXT:    [[TMP7:%.*]] = add i32 [[TMP3:%.*]], [[TMP2:%.*]]
-; CHECK-NEXT:    [[TMP8:%.*]] = add i32 [[TMP7]], [[TMP0:%.*]]
-; CHECK-NEXT:    [[TMP9:%.*]] = add i32 [[TMP8]], [[TMP1:%.*]]
-; CHECK-NEXT:    [[TMP10:%.*]] = add i32 [[TMP9]], [[TMP4:%.*]]
-; CHECK-NEXT:    [[TMP11:%.*]] = add i32 [[TMP10]], [[TMP5:%.*]]
+; CHECK-NEXT:    [[TMP7:%.*]] = add nsw i32 [[TMP3:%.*]], [[TMP2:%.*]]
+; CHECK-NEXT:    [[TMP8:%.*]] = add nsw i32 [[TMP7]], [[TMP0:%.*]]
+; CHECK-NEXT:    [[TMP9:%.*]] = add nsw i32 [[TMP8]], [[TMP1:%.*]]
+; CHECK-NEXT:    [[TMP10:%.*]] = add nsw i32 [[TMP9]], [[TMP4:%.*]]
+; CHECK-NEXT:    [[TMP11:%.*]] = add nsw i32 [[TMP10]], [[TMP5:%.*]]
 ; CHECK-NEXT:    store i32 [[TMP11]], i32* @num1, align 4
 ; CHECK-NEXT:    [[TMP12:%.*]] = add nsw i32 [[TMP5]], [[TMP0]]
 ; CHECK-NEXT:    store i32 [[TMP12]], i32* @num2, align 4
diff --git a/llvm/test/Transforms/Reassociate/no-op.ll b/llvm/test/Transforms/Reassociate/no-op.ll
--- a/llvm/test/Transforms/Reassociate/no-op.ll
+++ b/llvm/test/Transforms/Reassociate/no-op.ll
@@ -31,8 +31,8 @@
 ; The initial add doesn't change so should not lose the nsw flag.
 ; CHECK-LABEL: @test2(
 ; CHECK-NEXT:    [[A0:%.*]] = add nsw i32 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[A1:%.*]] = add i32 [[A0]], [[C:%.*]]
-; CHECK-NEXT:    [[A2:%.*]] = add i32 [[A1]], [[D:%.*]]
+; CHECK-NEXT:    [[A1:%.*]] = add nsw i32 [[A0]], [[C:%.*]]
+; CHECK-NEXT:    [[A2:%.*]] = add nsw i32 [[A1]], [[D:%.*]]
 ; CHECK-NEXT:    call void @use(i32 [[A2]])
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/Transforms/Reassociate/optional-flags.ll b/llvm/test/Transforms/Reassociate/optional-flags.ll
--- a/llvm/test/Transforms/Reassociate/optional-flags.ll
+++ b/llvm/test/Transforms/Reassociate/optional-flags.ll
@@ -19,8 +19,8 @@
 define i64 @test1(i64 %a, i64 %b, i64 %c) {
 ;
 ; CHECK-LABEL: @test1(
-; CHECK-NEXT:    [[Y:%.*]] = add i64 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[Z:%.*]] = add i64 [[Y]], [[C:%.*]]
+; CHECK-NEXT:    [[Y:%.*]] = add nsw i64 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    [[Z:%.*]] = add nsw i64 [[Y]], [[C:%.*]]
 ; CHECK-NEXT:    ret i64 [[Z]]
 ;
   %y = add i64 %c, %b
diff --git a/llvm/test/Transforms/Reassociate/vaarg_movable.ll b/llvm/test/Transforms/Reassociate/vaarg_movable.ll
--- a/llvm/test/Transforms/Reassociate/vaarg_movable.ll
+++ b/llvm/test/Transforms/Reassociate/vaarg_movable.ll
@@ -15,8 +15,8 @@
 ; CHECK-NEXT:    [[V0:%.*]] = va_arg i8** [[VARARGS]], i32
 ; CHECK-NEXT:    [[V1:%.*]] = va_arg i8** [[VARARGS]], i32
 ; CHECK-NEXT:    [[V0_NEG:%.*]] = sub i32 0, [[V0]]
-; CHECK-NEXT:    [[SUB:%.*]] = add i32 [[V0_NEG]], 1
-; CHECK-NEXT:    [[ADD:%.*]] = add i32 [[SUB]], [[V1]]
+; CHECK-NEXT:    [[SUB:%.*]] = add nsw i32 [[V0_NEG]], 1
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], [[V1]]
 ; CHECK-NEXT:    call void @llvm.va_end(i8* [[VARARGS1]])
 ; CHECK-NEXT:    ret i32 [[ADD]]
 ;
diff --git a/llvm/test/Transforms/Reassociate/wrap-flags.ll b/llvm/test/Transforms/Reassociate/wrap-flags.ll
--- a/llvm/test/Transforms/Reassociate/wrap-flags.ll
+++ b/llvm/test/Transforms/Reassociate/wrap-flags.ll
@@ -79,7 +79,7 @@
 ; CHECK-LABEL: @pr23926(
 ; CHECK-NEXT:    [[X1_NEG:%.*]] = sub i2 0, [[X1:%.*]]
 ; CHECK-NEXT:    [[ADD_NEG:%.*]] = add i2 [[X1_NEG]], -1
-; CHECK-NEXT:    [[SUB:%.*]] = add i2 [[ADD_NEG]], [[X2:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = add nuw nsw i2 [[ADD_NEG]], [[X2:%.*]]
 ; CHECK-NEXT:    ret i2 [[SUB]]
 ;
   %add = add nuw i2 %X1, 1