Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -891,6 +891,7 @@
 /// @brief Common integer divide transforms
 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+  bool IsSigned = I.getOpcode() == Instruction::SDiv;
 
   // The RHS is known non-zero.
   if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I)) {
@@ -908,7 +909,6 @@
     if (match(Op1, m_APInt(C2))) {
       Value *X;
       const APInt *C1;
-      bool IsSigned = I.getOpcode() == Instruction::SDiv;
 
       // (X / C1) / C2  -> X / (C1*C2)
       if ((IsSigned && match(LHS, m_SDiv(m_Value(X), m_APInt(C1)))) ||
@@ -1000,12 +1000,18 @@
 
   // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
   Value *X = nullptr, *Z = nullptr;
-  if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
-    bool isSigned = I.getOpcode() == Instruction::SDiv;
-    if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
-        (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
+  if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) // (X - Z) / Y; Y = Op1
+    if ((IsSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
+        (!IsSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
       return BinaryOperator::Create(I.getOpcode(), X, Op1);
-  }
+
+  // (X << Y) / X -> 1 << Y
+  Value *Y = nullptr;
+  Constant *C = ConstantInt::get(Op1->getType(), 1);
+  if (IsSigned && match(Op0, m_NSWShl(m_Specific(Op1), m_Value(Y))))
+    return BinaryOperator::CreateNSWShl(C, Y);
+  if (!IsSigned && match(Op0, m_NUWShl(m_Specific(Op1), m_Value(Y))))
+    return BinaryOperator::CreateNUWShl(C, Y);
 
   return nullptr;
 }
Index: test/Transforms/InstCombine/div-shift.ll
===================================================================
--- test/Transforms/InstCombine/div-shift.ll
+++ test/Transforms/InstCombine/div-shift.ll
@@ -98,3 +98,107 @@
   %y = udiv i32 %z, %divisor
   ret i32 %y
 }
+
+; (X << C1) / X -> 1 << C1 optimizations
+
+define i32 @t7(i32 %x) {
+; CHECK-LABEL: @t7(
+; CHECK:         ret i32 4
+;
+  %shl = shl nsw i32 %x, 2 
+  %r = sdiv i32 %shl, %x
+  ret i32 %r
+}
+
+; make sure the previous opt doesn't take place for wrapped shifts
+
+define i32 @t8(i32 %x) {
+; CHECK-LABEL: @t8(
+; CHECK:         %shl = shl i32 %x, 2
+; CHECK-NEXT:    %r = sdiv i32 %shl, %x
+; CHECK-NEXT:    ret i32 %r
+;
+  %shl = shl i32 %x, 2 
+  %r = sdiv i32 %shl, %x
+  ret i32 %r
+}
+
+define <2 x i32> @t9(<2 x i32> %x) {
+; CHECK-LABEL: @t9(
+; CHECK:         ret <2 x i32> <i32 4, i32 8>
+;
+  %shl = shl nsw <2 x i32> %x, <i32 2, i32 3>
+  %r = sdiv <2 x i32> %shl, %x
+  ret <2 x i32> %r
+}
+
+define i32 @t10(i32 %x, i32 %y) {
+; CHECK-LABEL: @t10(
+; CHECK:         %r = shl nsw i32 1, %y 
+; CHECK-NEXT:    ret i32 %r
+;
+  %shl = shl nsw i32 %x, %y 
+  %r = sdiv i32 %shl, %x
+  ret i32 %r
+}
+
+define <2 x i32> @t11(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @t11(
+; CHECK:         %r = shl nsw <2 x i32> <i32 1, i32 1>, %y 
+; CHECK-NEXT:    ret <2 x i32> %r
+;
+  %shl = shl nsw <2 x i32> %x, %y 
+  %r = sdiv <2 x i32> %shl, %x
+  ret <2 x i32> %r
+}
+
+define i32 @t12(i32 %x) {
+; CHECK-LABEL: @t12(
+; CHECK:         ret i32 4
+;
+  %shl = shl nuw i32 %x, 2 
+  %r = udiv i32 %shl, %x
+  ret i32 %r
+}
+
+; make sure the previous opt doesn't take place for wrapped shifts
+
+define i32 @t13(i32 %x) {
+; CHECK-LABEL: @t13(
+; CHECK:         %shl = shl i32 %x, 2
+; CHECK-NEXT:    %r = udiv i32 %shl, %x
+; CHECK-NEXT:    ret i32 %r
+;
+  %shl = shl i32 %x, 2 
+  %r = udiv i32 %shl, %x
+  ret i32 %r
+}
+
+define <2 x i32> @t14(<2 x i32> %x) {
+; CHECK-LABEL: @t14(
+; CHECK:         ret <2 x i32> <i32 4, i32 8>
+;
+  %shl = shl nuw <2 x i32> %x, <i32 2, i32 3>
+  %r = udiv <2 x i32> %shl, %x
+  ret <2 x i32> %r
+}
+
+define i32 @t15(i32 %x, i32 %y) {
+; CHECK-LABEL: @t15(
+; CHECK:         %r = shl nuw i32 1, %y 
+; CHECK-NEXT:    ret i32 %r
+;
+  %shl = shl nuw i32 %x, %y 
+  %r = udiv i32 %shl, %x
+  ret i32 %r
+}
+
+define <2 x i32> @t16(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @t16(
+; CHECK:         %r = shl nuw <2 x i32> <i32 1, i32 1>, %y 
+; CHECK-NEXT:    ret <2 x i32> %r
+;
+  %shl = shl nuw <2 x i32> %x, %y 
+  %r = udiv <2 x i32> %shl, %x
+  ret <2 x i32> %r
+}