diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -621,6 +621,11 @@
   Value *Op0 = II.getArgOperand(0);
   Value *X, *Y;
 
+  // ctpop(X) -> 1 iff X is non-zero power of 2. Maybe better also to just
+  // return icmp X, 0 if its known power of 2 but not known non-zero.
+  if (IC.isKnownToBeAPowerOfTwo(Op0, /* OrZero */ false))
+    return IC.replaceInstUsesWith(II, ConstantInt::get(Ty, 1));
+
   // ctpop(bitreverse(x)) -> ctpop(x)
   // ctpop(bswap(x)) -> ctpop(x)
   if (match(Op0, m_BitReverse(m_Value(X))) || match(Op0, m_BSwap(m_Value(X))))
diff --git a/llvm/test/Transforms/InstCombine/ctpop-pow2.ll b/llvm/test/Transforms/InstCombine/ctpop-pow2.ll
--- a/llvm/test/Transforms/InstCombine/ctpop-pow2.ll
+++ b/llvm/test/Transforms/InstCombine/ctpop-pow2.ll
@@ -9,9 +9,7 @@
 
 define i64 @ctpop_1_shl(i64 %x) {
 ; CHECK-LABEL: @ctpop_1_shl(
-; CHECK-NEXT:    [[V:%.*]] = shl nuw i64 1, [[X:%.*]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i64 @llvm.ctpop.i64(i64 [[V]]), !range [[RNG0:![0-9]+]]
-; CHECK-NEXT:    ret i64 [[CNT]]
+; CHECK-NEXT:    ret i64 1
 ;
   %v = shl i64 1, %x
   %cnt = call i64 @llvm.ctpop.i64(i64 %v)
@@ -20,9 +18,7 @@
 
 define i32 @ctpop_imin_lshr(i32 %x) {
 ; CHECK-LABEL: @ctpop_imin_lshr(
-; CHECK-NEXT:    [[V:%.*]] = lshr i32 -2147483648, [[X:%.*]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[V]]), !range [[RNG1:![0-9]+]]
-; CHECK-NEXT:    ret i32 [[CNT]]
+; CHECK-NEXT:    ret i32 1
 ;
   %v = lshr i32 2147483648, %x
   %cnt = call i32 @llvm.ctpop.i32(i32 %v)
@@ -33,7 +29,7 @@
 ; CHECK-LABEL: @ctpop_x_and_negx(
 ; CHECK-NEXT:    [[V0:%.*]] = sub i16 0, [[X:%.*]]
 ; CHECK-NEXT:    [[V1:%.*]] = and i16 [[V0]], [[X]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i16 @llvm.ctpop.i16(i16 [[V1]]), !range [[RNG2:![0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i16 @llvm.ctpop.i16(i16 [[V1]]), !range [[RNG0:![0-9]+]]
 ; CHECK-NEXT:    ret i16 [[CNT]]
 ;
   %v0 = sub i16 0, %x
@@ -47,7 +43,7 @@
 ; CHECK-NEXT:    [[X1:%.*]] = or i8 [[X:%.*]], 1
 ; CHECK-NEXT:    [[V0:%.*]] = sub nsw i8 0, [[X1]]
 ; CHECK-NEXT:    [[V1:%.*]] = and i8 [[X1]], [[V0]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctpop.i8(i8 [[V1]]), !range [[RNG3:![0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctpop.i8(i8 [[V1]]), !range [[RNG1:![0-9]+]]
 ; CHECK-NEXT:    ret i8 [[CNT]]
 ;
   %x1 = or i8 %x, 1
@@ -60,7 +56,7 @@
 define i32 @ctpop_2_shl(i32 %x) {
 ; CHECK-LABEL: @ctpop_2_shl(
 ; CHECK-NEXT:    [[V:%.*]] = shl i32 2, [[X:%.*]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[V]]), !range [[RNG4:![0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[V]]), !range [[RNG2:![0-9]+]]
 ; CHECK-NEXT:    ret i32 [[CNT]]
 ;
   %v = shl i32 2, %x
@@ -71,7 +67,7 @@
 define i16 @ctpop_imin_plus1_lshr(i16 %x) {
 ; CHECK-LABEL: @ctpop_imin_plus1_lshr(
 ; CHECK-NEXT:    [[V:%.*]] = lshr i16 -32767, [[X:%.*]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i16 @llvm.ctpop.i16(i16 [[V]]), !range [[RNG2]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i16 @llvm.ctpop.i16(i16 [[V]]), !range [[RNG0]]
 ; CHECK-NEXT:    ret i16 [[CNT]]
 ;
   %v = lshr i16 32769, %x
@@ -84,7 +80,7 @@
 ; CHECK-LABEL: @ctpop_2_shl_nz(
 ; CHECK-NEXT:    [[XA30:%.*]] = and i32 [[X:%.*]], 30
 ; CHECK-NEXT:    [[V:%.*]] = shl i32 2, [[XA30]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[V]]), !range [[RNG5:![0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[V]]), !range [[RNG3:![0-9]+]]
 ; CHECK-NEXT:    ret i32 [[CNT]]
 ;
   %xa30 = and i32 30, %x
@@ -98,7 +94,7 @@
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[X:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
 ; CHECK-NEXT:    [[V:%.*]] = lshr i8 -127, [[X]]
-; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctpop.i8(i8 [[V]]), !range [[RNG6:![0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctpop.i8(i8 [[V]]), !range [[RNG4:![0-9]+]]
 ; CHECK-NEXT:    ret i8 [[CNT]]
 ;
   %cmp = icmp ne i8 %x, 0
@@ -115,7 +111,7 @@
 ; CHECK-NEXT:    [[V1:%.*]] = and i64 [[V0]], [[X]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i64 [[V1]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
-; CHECK-NEXT:    [[CNT:%.*]] = call i64 @llvm.ctpop.i64(i64 [[V1]]), !range [[RNG0]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i64 @llvm.ctpop.i64(i64 [[V1]]), !range [[RNG5:![0-9]+]]
 ; CHECK-NEXT:    ret i64 [[CNT]]
 ;
   %v0 = sub i64 0, %x