Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1052,17 +1052,17 @@
 
   // X / 1 -> X
   // X % 1 -> 0
-  // If this is a boolean op (single-bit element type), we can't have
-  // division-by-zero or remainder-by-zero, so assume the divisor is 1.
-  // Similarly, if we're zero-extending a boolean divisor, then assume it's a 1.
-  Value *X;
-  if (match(Op1, m_One()) || Ty->isIntOrIntVectorTy(1) ||
-      (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)))
+  // If the divisor can only be zero or one, we can't have division-by-zero 
+  // or remainder-by-zero, so assume the divisor is 1.
+  //   e.g. 1, zext (i8 X), sdiv X (Y and 1)
+  KnownBits Known = computeKnownBits(Op1, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
+  if (Known.countMinLeadingZeros() >= Known.getBitWidth() - 1)
     return IsDiv ? Op0 : Constant::getNullValue(Ty);
 
   // If X * Y does not overflow, then:
   //   X * Y / Y -> X
   //   X * Y % Y -> 0
+  Value *X;
   if (match(Op0, m_c_Mul(m_Value(X), m_Specific(Op1)))) {
     auto *Mul = cast<OverflowingBinaryOperator>(Op0);
     // The multiplication can't overflow if it is defined not to, or if
Index: llvm/test/Transforms/InstCombine/zext-or-icmp.ll
===================================================================
--- llvm/test/Transforms/InstCombine/zext-or-icmp.ll
+++ llvm/test/Transforms/InstCombine/zext-or-icmp.ll
@@ -248,7 +248,7 @@
 ; CHECK-NEXT:    store i32 [[ADD]], ptr [[F]], align 4
 ; CHECK-NEXT:    [[REM18:%.*]] = srem i32 [[LOR_EXT]], [[ADD]]
 ; CHECK-NEXT:    [[CONV19:%.*]] = zext i32 [[REM18]] to i64
-; CHECK-NEXT:    store i32 0, ptr [[D]], align 8
+; CHECK-NEXT:    store i32 [[SROA38]], ptr [[D]], align 8
 ; CHECK-NEXT:    [[R:%.*]] = icmp ult i64 [[INSERT_INSERT41]], [[CONV19]]
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[R]])
 ; CHECK-NEXT:    ret i1 true
Index: llvm/test/Transforms/InstSimplify/div.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/div.ll
+++ llvm/test/Transforms/InstSimplify/div.ll
@@ -437,9 +437,7 @@
 
 define i32 @sdiv_one_srem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @sdiv_one_srem_divisor(
-; CHECK-NEXT:    [[SREM:%.*]] = srem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv i32 [[A:%.*]], [[SREM]]
-; CHECK-NEXT:    ret i32 [[SDIV]]
+; CHECK-NEXT:    ret i32 [[A:%.*]]
 ;
   %srem = srem i32 1, %b
   %sdiv = sdiv i32 %a, %srem
@@ -448,9 +446,7 @@
 
 define i32 @sdiv_one_urem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @sdiv_one_urem_divisor(
-; CHECK-NEXT:    [[UREM:%.*]] = urem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv i32 [[A:%.*]], [[UREM]]
-; CHECK-NEXT:    ret i32 [[SDIV]]
+; CHECK-NEXT:    ret i32 [[A:%.*]]
 ;
   %urem = urem i32 1, %b
   %sdiv = sdiv i32 %a, %urem
@@ -459,9 +455,7 @@
 
 define i32 @udiv_one_srem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @udiv_one_srem_divisor(
-; CHECK-NEXT:    [[SREM:%.*]] = srem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[UDIV:%.*]] = udiv i32 [[A:%.*]], [[SREM]]
-; CHECK-NEXT:    ret i32 [[UDIV]]
+; CHECK-NEXT:    ret i32 [[A:%.*]]
 ;
   %srem = srem i32 1, %b
   %udiv = udiv i32 %a, %srem
@@ -470,9 +464,7 @@
 
 define i32 @udiv_one_urem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @udiv_one_urem_divisor(
-; CHECK-NEXT:    [[UREM:%.*]] = urem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[UDIV:%.*]] = udiv i32 [[A:%.*]], [[UREM]]
-; CHECK-NEXT:    ret i32 [[UDIV]]
+; CHECK-NEXT:    ret i32 [[A:%.*]]
 ;
   %urem = urem i32 1, %b
   %udiv = udiv i32 %a, %urem
@@ -481,9 +473,7 @@
 
 define i32 @srem_one_srem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @srem_one_srem_divisor(
-; CHECK-NEXT:    [[SREM:%.*]] = srem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[SREM1:%.*]] = srem i32 [[A:%.*]], [[SREM]]
-; CHECK-NEXT:    ret i32 [[SREM1]]
+; CHECK-NEXT:    ret i32 0
 ;
   %srem = srem i32 1, %b
   %srem1 = srem i32 %a, %srem
@@ -492,9 +482,7 @@
 
 define i32 @urem_one_srem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @urem_one_srem_divisor(
-; CHECK-NEXT:    [[SREM:%.*]] = srem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[UREM:%.*]] = urem i32 [[A:%.*]], [[SREM]]
-; CHECK-NEXT:    ret i32 [[UREM]]
+; CHECK-NEXT:    ret i32 0
 ;
   %srem = srem i32 1, %b
   %urem = urem i32 %a, %srem
@@ -503,9 +491,7 @@
 
 define i32 @srem_one_urem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @srem_one_urem_divisor(
-; CHECK-NEXT:    [[UREM:%.*]] = urem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[SREM:%.*]] = srem i32 [[A:%.*]], [[UREM]]
-; CHECK-NEXT:    ret i32 [[SREM]]
+; CHECK-NEXT:    ret i32 0
 ;
   %urem = urem i32 1, %b
   %srem = srem i32 %a, %urem
@@ -514,9 +500,7 @@
 
 define i32 @urem_one_urem_divisor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @urem_one_urem_divisor(
-; CHECK-NEXT:    [[UREM:%.*]] = urem i32 1, [[B:%.*]]
-; CHECK-NEXT:    [[UREM1:%.*]] = urem i32 [[A:%.*]], [[UREM]]
-; CHECK-NEXT:    ret i32 [[UREM1]]
+; CHECK-NEXT:    ret i32 0
 ;
   %urem = urem i32 1, %b
   %urem1 = urem i32 %a, %urem
@@ -525,9 +509,7 @@
 
 define <2 x i8> @sdiv_one_vec_srem_divisor(<2 x i8> %a, <2 x i8> %b) {
 ; CHECK-LABEL: @sdiv_one_vec_srem_divisor(
-; CHECK-NEXT:    [[SREM:%.*]] = srem <2 x i8> <i8 1, i8 1>, [[B:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv <2 x i8> [[A:%.*]], [[SREM]]
-; CHECK-NEXT:    ret <2 x i8> [[SDIV]]
+; CHECK-NEXT:    ret <2 x i8> [[A:%.*]]
 ;
   %srem = srem <2 x i8> <i8 1, i8 1>, %b
   %sdiv = sdiv <2 x i8> %a, %srem
@@ -536,9 +518,7 @@
 
 define i32 @sdiv_and_one_divisor(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sdiv_and_one_divisor(
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], 1
-; CHECK-NEXT:    [[RES:%.*]] = sdiv i32 [[Y:%.*]], [[AND]]
-; CHECK-NEXT:    ret i32 [[RES]]
+; CHECK-NEXT:    ret i32 [[Y:%.*]]
 ;
   %and = and i32 %x, 1
   %res = sdiv i32 %y, %and
@@ -547,9 +527,7 @@
 
 define <2 x i8> @sdiv_and_one_vec_divisor(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @sdiv_and_one_vec_divisor(
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i8> [[X:%.*]], <i8 1, i8 1>
-; CHECK-NEXT:    [[RES:%.*]] = sdiv <2 x i8> [[Y:%.*]], [[AND]]
-; CHECK-NEXT:    ret <2 x i8> [[RES]]
+; CHECK-NEXT:    ret <2 x i8> [[Y:%.*]]
 ;
   %and = and <2 x i8> %x, <i8 1, i8 1>
   %res = sdiv <2 x i8> %y, %and
@@ -558,10 +536,7 @@
 
 define i32 @sdiv_neg_or_divisor(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sdiv_neg_or_divisor(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X:%.*]], -2
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[OR]], -1
-; CHECK-NEXT:    [[RES:%.*]] = sdiv i32 [[Y:%.*]], [[NEG]]
-; CHECK-NEXT:    ret i32 [[RES]]
+; CHECK-NEXT:    ret i32 [[Y:%.*]]
 ;
   %or = or i32 %x, -2
   %neg = xor i32 %or, -1