Index: llvm/include/llvm/Analysis/ValueTracking.h
===================================================================
--- llvm/include/llvm/Analysis/ValueTracking.h
+++ llvm/include/llvm/Analysis/ValueTracking.h
@@ -102,7 +102,10 @@
                       const DominatorTree *DT = nullptr);
 
   /// Return true if the two given values are negation.
-  bool isKnownNegation(const Value *X, const Value *Y);
+  /// Currently can recoginze Value pair:
+  /// 1: <X, Y> if X = sub (0, Y) or Y = sub (0, X)
+  /// 2: <X, Y> if X = sub (A, B) and Y = sub (B, A)
+  bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW = false);
 
   /// Returns true if the give value is known to be non-negative.
   bool isKnownNonNegative(const Value *V, const DataLayout &DL,
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1081,6 +1081,10 @@
 /// If not, this returns null.
 static Value *SimplifySDivInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
                                unsigned MaxRecurse) {
+  // If two operands are negated and no signed overflow, return -1.
+  if (isKnownNegation(Op0, Op1, /*NeedNSW=*/true))
+    return Constant::getAllOnesValue(Op0->getType());
+
   return simplifyDiv(Instruction::SDiv, Op0, Op1, Q, MaxRecurse);
 }
 
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4511,21 +4511,25 @@
   return {SPF_UNKNOWN, SPNB_NA, false};
 }
 
-bool llvm::isKnownNegation(const Value *X, const Value *Y) {
+bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
   assert(X && Y && "Invalid operand");
 
-  // X = sub (0, Y)
-  if (match(X, m_Neg(m_Specific(Y))))
+  // X = sub (0, Y) || X = sub nsw (0, Y)
+  if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
+      (NeedNSW && match(X, m_NSWSub(m_ZeroInt(), m_Specific(Y)))))
     return true;
 
-  // Y = sub (0, X)
-  if (match(Y, m_Neg(m_Specific(X))))
+  // Y = sub (0, X) || Y = sub nsw (0, X)
+  if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
+      (NeedNSW && match(Y, m_NSWSub(m_ZeroInt(), m_Specific(X)))))
     return true;
 
-  // X = sub (A, B), Y = sub (B, A)
+  // X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
   Value *A, *B;
-  return match(X, m_Sub(m_Value(A), m_Value(B))) &&
-         match(Y, m_Sub(m_Specific(B), m_Specific(A)));
+  return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
+                        match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
+         (NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
+                       match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
 }
 
 static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
Index: llvm/test/Transforms/InstSimplify/sdiv.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/sdiv.ll
+++ llvm/test/Transforms/InstSimplify/sdiv.ll
@@ -1,10 +1,9 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -instsimplify -S | FileCheck %s
 
 define i32 @negated_operand(i32 %x) {
 ; CHECK-LABEL: @negated_operand(
-; CHECK-NEXT:    [[NEGX:%.*]] = sub nsw i32 0, [[X:%.*]]
-; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[NEGX]], [[X]]
-; CHECK-NEXT:    ret i32 [[DIV]]
+; CHECK-NEXT:    ret i32 -1
 ;
   %negx = sub nsw i32 0, %x
   %div = sdiv i32 %negx, %x
@@ -13,9 +12,7 @@
 
 define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
 ; CHECK-LABEL: @negated_operand_commute_vec(
-; CHECK-NEXT:    [[NEGX:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
-; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[NEGX]], [[X]]
-; CHECK-NEXT:    ret <2 x i32> [[DIV]]
+; CHECK-NEXT:    ret <2 x i32> <i32 -1, i32 -1>
 ;
   %negx = sub nsw <2 x i32> zeroinitializer, %x
   %div = sdiv <2 x i32> %negx, %x
@@ -24,26 +21,159 @@
 
 define i32 @knownnegation(i32 %x, i32 %y) {
 ; CHECK-LABEL: @knownnegation(
+; CHECK-NEXT:    ret i32 -1
+;
+  %xy = sub nsw i32 %x, %y
+  %yx = sub nsw i32 %y, %x
+  %div = sdiv i32 %xy, %yx
+  ret i32 %div
+}
+
+define <2 x i32> @knownnegation_commute_vec(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @knownnegation_commute_vec(
+; CHECK-NEXT:    ret <2 x i32> <i32 -1, i32 -1>
+;
+  %xy = sub nsw <2 x i32> %x, %y
+  %yx = sub nsw <2 x i32> %y, %x
+  %div = sdiv <2 x i32> %xy, %yx
+  ret <2 x i32> %div
+}
+
+define i32 @negated_operand_2(i32 %t) {
+; CHECK-LABEL: @negated_operand_2(
+; CHECK-NEXT:    ret i32 -1
+;
+  %x = sub i32 %t, 5 
+  %negx = sub nsw i32 0, %x
+  %div = sdiv i32 %negx, %x
+  ret i32 %div
+}
+
+define i32 @negated_operand_commute(i32 %x) {
+; CHECK-LABEL: @negated_operand_commute(
+; CHECK-NEXT:    ret i32 -1
+;
+  %negx = sub nsw i32 0, %x
+  %div = sdiv i32 %x, %negx
+  ret i32 %div
+}
+
+define i32 @negated_operand_bad(i32 %x) {
+; CHECK-LABEL: @negated_operand_bad(
+; CHECK-NEXT:    [[NEGX:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[NEGX]], [[X]]
+; CHECK-NEXT:    ret i32 [[DIV]]
+;
+  %negx = sub i32 0, %x ; not nsw
+  %div = sdiv i32 %negx, %x
+  ret i32 %div
+}
+
+define i32 @knownnegation_bad_1(i32 %x, i32 %y) {
+; CHECK-LABEL: @knownnegation_bad_1(
 ; CHECK-NEXT:    [[XY:%.*]] = sub nsw i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[YX:%.*]] = sub nsw i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[YX:%.*]] = sub i32 [[Y]], [[X]]
 ; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[XY]], [[YX]]
 ; CHECK-NEXT:    ret i32 [[DIV]]
 ;
   %xy = sub nsw i32 %x, %y
+  %yx = sub i32 %y, %x ; not nsw
+  %div = sdiv i32 %xy, %yx
+  ret i32 %div
+}
+
+define i32 @knownnegation_bad_2(i32 %x, i32 %y) {
+; CHECK-LABEL: @knownnegation_bad_2(
+; CHECK-NEXT:    [[XY:%.*]] = sub i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[YX:%.*]] = sub nsw i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[XY]], [[YX]]
+; CHECK-NEXT:    ret i32 [[DIV]]
+;
+  %xy = sub i32 %x, %y ; not nsw
   %yx = sub nsw i32 %y, %x
   %div = sdiv i32 %xy, %yx
   ret i32 %div
 }
 
-define <2 x i32> @knownnegation_commute_vec(<2 x i32> %x, <2 x i32> %y) {
-; CHECK-LABEL: @knownnegation_commute_vec(
+define i32 @knownnegation_bad_3(i32 %x, i32 %y) {
+; CHECK-LABEL: @knownnegation_bad_3(
+; CHECK-NEXT:    [[XY:%.*]] = sub i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[YX:%.*]] = sub i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[XY]], [[YX]]
+; CHECK-NEXT:    ret i32 [[DIV]]
+;
+  %xy = sub i32 %x, %y ; not nsw
+  %yx = sub i32 %y, %x ; not nsw
+  %div = sdiv i32 %xy, %yx
+  ret i32 %div
+}
+
+define <2 x i32> @negated_operand_commute_vec_bad(<2 x i32> %x) {
+; CHECK-LABEL: @negated_operand_commute_vec_bad(
+; CHECK-NEXT:    [[NEGX:%.*]] = sub <2 x i32> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[NEGX]], [[X]]
+; CHECK-NEXT:    ret <2 x i32> [[DIV]]
+;
+  %negx = sub <2 x i32> zeroinitializer, %x ; not nsw
+  %div = sdiv <2 x i32> %negx, %x
+  ret <2 x i32> %div
+}
+
+define <2 x i32> @knownnegation_commute_vec_bad1(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @knownnegation_commute_vec_bad1(
 ; CHECK-NEXT:    [[XY:%.*]] = sub nsw <2 x i32> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[YX:%.*]] = sub nsw <2 x i32> [[Y]], [[X]]
+; CHECK-NEXT:    [[YX:%.*]] = sub <2 x i32> [[Y]], [[X]]
 ; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[XY]], [[YX]]
 ; CHECK-NEXT:    ret <2 x i32> [[DIV]]
 ;
   %xy = sub nsw <2 x i32> %x, %y
+  %yx = sub <2 x i32> %y, %x ; not nsw
+  %div = sdiv <2 x i32> %xy, %yx
+  ret <2 x i32> %div
+}
+
+define <2 x i32> @knownnegation_commute_vec_bad2(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @knownnegation_commute_vec_bad2(
+; CHECK-NEXT:    [[XY:%.*]] = sub <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[YX:%.*]] = sub nsw <2 x i32> [[Y]], [[X]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[XY]], [[YX]]
+; CHECK-NEXT:    ret <2 x i32> [[DIV]]
+;
+  %xy = sub <2 x i32> %x, %y ; not nsw
   %yx = sub nsw <2 x i32> %y, %x
   %div = sdiv <2 x i32> %xy, %yx
   ret <2 x i32> %div
 }
+
+define <2 x i32> @knownnegation_commute_vec_bad3(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @knownnegation_commute_vec_bad3(
+; CHECK-NEXT:    [[XY:%.*]] = sub <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[YX:%.*]] = sub <2 x i32> [[Y]], [[X]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[XY]], [[YX]]
+; CHECK-NEXT:    ret <2 x i32> [[DIV]]
+;
+  %xy = sub <2 x i32> %x, %y ; not nsw
+  %yx = sub <2 x i32> %y, %x ; not nsw
+  %div = sdiv <2 x i32> %xy, %yx
+  ret <2 x i32> %div
+}
+
+define <3 x i32> @negated_operand_vec_undef(<3 x i32> %x) {
+; CHECK-LABEL: @negated_operand_vec_undef(
+; CHECK-NEXT:    ret <3 x i32> <i32 -1, i32 -1, i32 -1>
+;
+  %negx = sub nsw <3 x i32> <i32 0, i32 undef, i32 0>, %x
+  %div = sdiv <3 x i32> %negx, %x
+  ret <3 x i32> %div
+}
+
+define <2 x i32> @negated_operand_vec_nonsplat(<2 x i32> %x) {
+; CHECK-LABEL: @negated_operand_vec_nonsplat(
+; CHECK-NEXT:    [[NEGX:%.*]] = sub nsw <2 x i32> <i32 0, i32 1>, [[X:%.*]]
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[NEGX]], [[X]]
+; CHECK-NEXT:    ret <2 x i32> [[DIV]]
+;
+  %negx = sub nsw <2 x i32> <i32 0, i32 1>, %x ; not 0, don't fold
+  %div = sdiv <2 x i32> %negx, %x
+  ret <2 x i32> %div
+}