diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1566,6 +1566,19 @@
       NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
       return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
     }
+
+    // Simplify:
+    //   (icmp eq (trunc (1 << Y) to i[N]), 0) --> (icmp ugt Y, N-1)
+    //   (icmp ne (trunc (1 << Y) to i[N]), 0) --> (icmp ult Y, N)
+    Value *Y;
+    if (match(X, m_Shl(m_One(), m_Value(Y)))) {
+      if (Pred == ICmpInst::ICMP_EQ)
+        return new ICmpInst(ICmpInst::ICMP_UGT, Y,
+                            ConstantInt::get(X->getType(), DstBits - 1));
+      else
+        return new ICmpInst(ICmpInst::ICMP_ULT, Y,
+                            ConstantInt::get(X->getType(), DstBits));
+    }
   }
 
   // Look through truncated right-shift of the sign-bit for a sign-bit check:
diff --git a/llvm/test/Transforms/InstCombine/icmp-trunc-shl.ll b/llvm/test/Transforms/InstCombine/icmp-trunc-shl.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/icmp-trunc-shl.ll
@@ -0,0 +1,332 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define i1 @eq_i32_to_i16(i32 %a) {
+; CHECK-LABEL: @eq_i32_to_i16(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i32 [[A:%.*]], 15
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i16
+  %r = icmp eq i16 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i32_to_i8(i32 %a) {
+; CHECK-LABEL: @eq_i32_to_i8(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i32 [[A:%.*]], 7
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i8
+  %r = icmp eq i8 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i32_to_i4(i32 %a) {
+; CHECK-LABEL: @eq_i32_to_i4(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i32 [[A:%.*]], 3
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i4
+  %r = icmp eq i4 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i32_to_i2(i32 %a) {
+; CHECK-LABEL: @eq_i32_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i32 [[A:%.*]], 1
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i2
+  %r = icmp eq i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i32_to_i1(i32 %a) {
+; CHECK-LABEL: @eq_i32_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i32 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i1
+  %r = icmp eq i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i16_to_i8(i16 %a) {
+; CHECK-LABEL: @eq_i16_to_i8(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i16 [[A:%.*]], 7
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i8
+  %r = icmp eq i8 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i16_to_i4(i16 %a) {
+; CHECK-LABEL: @eq_i16_to_i4(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i16 [[A:%.*]], 3
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i4
+  %r = icmp eq i4 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i16_to_i2(i16 %a) {
+; CHECK-LABEL: @eq_i16_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i16 [[A:%.*]], 1
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i2
+  %r = icmp eq i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i16_to_i1(i16 %a) {
+; CHECK-LABEL: @eq_i16_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i16 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i1
+  %r = icmp eq i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i8_to_i4(i8 %a) {
+; CHECK-LABEL: @eq_i8_to_i4(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[A:%.*]], 3
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i8 1, %a
+  %t = trunc i8 %shl to i4
+  %r = icmp eq i4 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i8_to_i2(i8 %a) {
+; CHECK-LABEL: @eq_i8_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[A:%.*]], 1
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i8 1, %a
+  %t = trunc i8 %shl to i2
+  %r = icmp eq i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i8_to_i1(i8 %a) {
+; CHECK-LABEL: @eq_i8_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i8 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i8 1, %a
+  %t = trunc i8 %shl to i1
+  %r = icmp eq i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i4_to_i2(i4 %a) {
+; CHECK-LABEL: @eq_i4_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i4 [[A:%.*]], 1
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i4 1, %a
+  %t = trunc i4 %shl to i2
+  %r = icmp eq i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i4_to_i1(i4 %a) {
+; CHECK-LABEL: @eq_i4_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i4 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i4 1, %a
+  %t = trunc i4 %shl to i1
+  %r = icmp eq i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @eq_i2_to_i1(i2 %a) {
+; CHECK-LABEL: @eq_i2_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i2 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i2 1, %a
+  %t = trunc i2 %shl to i1
+  %r = icmp eq i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i32_to_i16(i32 %a) {
+; CHECK-LABEL: @ne_i32_to_i16(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i32 [[A:%.*]], 16
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i16
+  %r = icmp ne i16 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i32_to_i8(i32 %a) {
+; CHECK-LABEL: @ne_i32_to_i8(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i32 [[A:%.*]], 8
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i8
+  %r = icmp ne i8 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i32_to_i4(i32 %a) {
+; CHECK-LABEL: @ne_i32_to_i4(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i32 [[A:%.*]], 4
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i4
+  %r = icmp ne i4 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i32_to_i2(i32 %a) {
+; CHECK-LABEL: @ne_i32_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i32 [[A:%.*]], 2
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i2
+  %r = icmp ne i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i32_to_i1(i32 %a) {
+; CHECK-LABEL: @ne_i32_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i32 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i32 1, %a
+  %t = trunc i32 %shl to i1
+  %r = icmp ne i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i16_to_i8(i16 %a) {
+; CHECK-LABEL: @ne_i16_to_i8(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i16 [[A:%.*]], 8
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i8
+  %r = icmp ne i8 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i16_to_i4(i16 %a) {
+; CHECK-LABEL: @ne_i16_to_i4(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i16 [[A:%.*]], 4
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i4
+  %r = icmp ne i4 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i16_to_i2(i16 %a) {
+; CHECK-LABEL: @ne_i16_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i16 [[A:%.*]], 2
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i2
+  %r = icmp ne i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i16_to_i1(i16 %a) {
+; CHECK-LABEL: @ne_i16_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i16 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i16 1, %a
+  %t = trunc i16 %shl to i1
+  %r = icmp ne i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i8_to_i4(i8 %a) {
+; CHECK-LABEL: @ne_i8_to_i4(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[A:%.*]], 4
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i8 1, %a
+  %t = trunc i8 %shl to i4
+  %r = icmp ne i4 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i8_to_i2(i8 %a) {
+; CHECK-LABEL: @ne_i8_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i8 [[A:%.*]], 2
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i8 1, %a
+  %t = trunc i8 %shl to i2
+  %r = icmp ne i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i8_to_i1(i8 %a) {
+; CHECK-LABEL: @ne_i8_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i8 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i8 1, %a
+  %t = trunc i8 %shl to i1
+  %r = icmp ne i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i4_to_i2(i4 %a) {
+; CHECK-LABEL: @ne_i4_to_i2(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i4 [[A:%.*]], 2
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %shl = shl i4 1, %a
+  %t = trunc i4 %shl to i2
+  %r = icmp ne i2 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i4_to_i1(i4 %a) {
+; CHECK-LABEL: @ne_i4_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i4 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i4 1, %a
+  %t = trunc i4 %shl to i1
+  %r = icmp ne i1 %t, 0
+  ret i1 %r
+}
+
+define i1 @ne_i2_to_i1(i2 %a) {
+; CHECK-LABEL: @ne_i2_to_i1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i2 [[A:%.*]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
+;
+  %shl = shl i2 1, %a
+  %t = trunc i2 %shl to i1
+  %r = icmp ne i1 %t, 0
+  ret i1 %r
+}