Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4909,8 +4909,7 @@
   return nullptr;
 }
 
-static Instruction *foldICmpWithTrunc(ICmpInst &ICmp,
-                                      InstCombiner::BuilderTy &Builder) {
+Instruction *InstCombinerImpl::foldICmpWithTrunc(ICmpInst &ICmp) {
   ICmpInst::Predicate Pred = ICmp.getPredicate();
   Value *Op0 = ICmp.getOperand(0), *Op1 = ICmp.getOperand(1);
 
@@ -4948,6 +4947,21 @@
     return new ICmpInst(ICmpInst::ICMP_EQ, And, MaskC);
   }
 
+  if (auto *II = dyn_cast<IntrinsicInst>(X)) {
+    if (II->getIntrinsicID() == Intrinsic::cttz ||
+        II->getIntrinsicID() == Intrinsic::ctlz) {
+      unsigned MaxRet = SrcBits;
+      if (match(II->getArgOperand(1), m_One()))
+        MaxRet--;
+
+      // Make sure the dest bits is enough to save the intrinsic output's range
+      if (llvm::Log2_32(MaxRet) + 1 <= Op0->getType()->getScalarSizeInBits())
+        if (Instruction *I =
+                foldICmpIntrinsicWithConstant(ICmp, II, C->zext(SrcBits)))
+          return I;
+    }
+  }
+
   return nullptr;
 }
 
@@ -5105,7 +5119,7 @@
       return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
   }
 
-  if (Instruction *R = foldICmpWithTrunc(ICmp, Builder))
+  if (Instruction *R = foldICmpWithTrunc(ICmp))
     return R;
 
   return foldICmpWithZextOrSext(ICmp);
Index: llvm/lib/Transforms/InstCombine/InstCombineInternal.h
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -624,6 +624,7 @@
   Instruction *foldICmpEqIntrinsicWithConstant(ICmpInst &ICI, IntrinsicInst *II,
                                                const APInt &C);
   Instruction *foldICmpBitCast(ICmpInst &Cmp);
+  Instruction *foldICmpWithTrunc(ICmpInst &Cmp);
 
   // Helpers of visitSelectInst().
   Instruction *foldSelectOfBools(SelectInst &SI);
Index: llvm/test/Transforms/InstCombine/cmp-intrinsic.ll
===================================================================
--- llvm/test/Transforms/InstCombine/cmp-intrinsic.ll
+++ llvm/test/Transforms/InstCombine/cmp-intrinsic.ll
@@ -4,13 +4,16 @@
 declare i16 @llvm.bswap.i16(i16)
 declare i32 @llvm.bswap.i32(i32)
 declare <2 x i64> @llvm.bswap.v2i64(<2 x i64>)
+declare i32 @llvm.cttz.i32(i32, i1)
 declare i33 @llvm.cttz.i33(i33, i1)
 declare i32 @llvm.ctlz.i32(i32, i1)
+declare i33 @llvm.ctlz.i33(i33, i1)
 declare i8 @llvm.ctpop.i8(i8)
 declare i11 @llvm.ctpop.i11(i11)
 declare <2 x i32> @llvm.cttz.v2i32(<2 x i32>, i1)
 declare <2 x i32> @llvm.ctlz.v2i32(<2 x i32>, i1)
 declare <2 x i32> @llvm.ctpop.v2i32(<2 x i32>)
+declare void @use6(i6)
 
 define i1 @bswap_eq_i16(i16 %x) {
 ; CHECK-LABEL: @bswap_eq_i16(
@@ -538,16 +541,84 @@
   ret i1 %cmp
 }
 
-define i1 @trunc_cttz_ult_other_i33_i15(i33 %x) {
-; CHECK-LABEL: @trunc_cttz_ult_other_i33_i15(
-; CHECK-NEXT:    [[TZ:%.*]] = tail call i33 @llvm.cttz.i33(i33 [[X:%.*]], i1 false), !range [[RNG1]]
-; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i33 [[TZ]] to i15
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i15 [[TRUNC]], 7
+define i1 @trunc_cttz_ult_other_i33_i6(i33 %x) {
+; CHECK-LABEL: @trunc_cttz_ult_other_i33_i6(
+; CHECK-NEXT:    [[TMP1:%.*]] = and i33 [[X:%.*]], 127
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i33 [[TMP1]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
-  %tz = tail call i33 @llvm.cttz.i33(i33 %x, i1 false)
-  %trunc = trunc i33 %tz to i15
-  %cmp = icmp ult i15 %trunc, 7
+  %tz = tail call i33 @llvm.cttz.i33(i33 %x, i1 true)
+  %trunc = trunc i33 %tz to i6
+  %cmp = icmp ult i6 %trunc, 7
+  ret i1 %cmp
+}
+
+define i1 @trunc_cttz_ult_other_i33_i5(i33 %x) {
+; CHECK-LABEL: @trunc_cttz_ult_other_i33_i5(
+; CHECK-NEXT:    [[TZ:%.*]] = tail call i33 @llvm.cttz.i33(i33 [[X:%.*]], i1 true), !range [[RNG1]]
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i33 [[TZ]] to i5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i5 [[TRUNC]], 7
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %tz = tail call i33 @llvm.cttz.i33(i33 %x, i1 true)
+  %trunc = trunc i33 %tz to i5
+  %cmp = icmp ult i5 %trunc, 7
+  ret i1 %cmp
+}
+
+define i1 @trunc_cttz_true_ult_other_i32_i5(i32 %x) {
+; CHECK-LABEL: @trunc_cttz_true_ult_other_i32_i5(
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[X:%.*]], 127
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[TMP1]], 0
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %tz = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
+  %trunc = trunc i32 %tz to i5
+  %cmp = icmp ult i5 %trunc, 7
+  ret i1 %cmp
+}
+
+; negative case, is_zero_poison == false && log2(src bitwidth) == dest bitwidth
+
+define i1 @trunc_cttz_false_ult_other_i32_i5(i32 %x) {
+; CHECK-LABEL: @trunc_cttz_false_ult_other_i32_i5(
+; CHECK-NEXT:    [[TZ:%.*]] = tail call i32 @llvm.cttz.i32(i32 [[X:%.*]], i1 false), !range [[RNG0]]
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i32 [[TZ]] to i5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i5 [[TRUNC]], 7
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %tz = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
+  %trunc = trunc i32 %tz to i5
+  %cmp = icmp ult i5 %trunc, 7
+  ret i1 %cmp
+}
+
+define i1 @trunc_cttz_false_ult_other_i32_i6(i32 %x) {
+; CHECK-LABEL: @trunc_cttz_false_ult_other_i32_i6(
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[X:%.*]], 127
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[TMP1]], 0
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %tz = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
+  %trunc = trunc i32 %tz to i6
+  %cmp = icmp ult i6 %trunc, 7
+  ret i1 %cmp
+}
+
+; negative case, trunc is not one use
+
+define i1 @trunc_cttz_false_ult_other_i32_i6_extra_use(i32 %x) {
+; CHECK-LABEL: @trunc_cttz_false_ult_other_i32_i6_extra_use(
+; CHECK-NEXT:    [[TZ:%.*]] = tail call i32 @llvm.cttz.i32(i32 [[X:%.*]], i1 false), !range [[RNG0]]
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i32 [[TZ]] to i6
+; CHECK-NEXT:    call void @use6(i6 [[TRUNC]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i6 [[TRUNC]], 7
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %tz = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
+  %trunc = trunc i32 %tz to i6
+  call void @use6(i6 %trunc)
+  %cmp = icmp ult i6 %trunc, 7
   ret i1 %cmp
 }
 
@@ -573,16 +644,81 @@
   ret i1 %cmp
 }
 
-define i1 @trunc_ctlz_ugt_other_i32(i32 %x) {
-; CHECK-LABEL: @trunc_ctlz_ugt_other_i32(
+define i1 @trunc_ctlz_ugt_other_i33_i6(i33 %x) {
+; CHECK-LABEL: @trunc_ctlz_ugt_other_i33_i6(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i33 [[X:%.*]], 268435456
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %lz = tail call i33 @llvm.ctlz.i33(i33 %x, i1 true)
+  %trunc = trunc i33 %lz to i6
+  %cmp = icmp ugt i6 %trunc, 4
+  ret i1 %cmp
+}
+
+define i1 @trunc_ctlz_ugt_other_i33_i5(i33 %x) {
+; CHECK-LABEL: @trunc_ctlz_ugt_other_i33_i5(
+; CHECK-NEXT:    [[LZ:%.*]] = tail call i33 @llvm.ctlz.i33(i33 [[X:%.*]], i1 true), !range [[RNG1]]
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i33 [[LZ]] to i5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i5 [[TRUNC]], 4
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %lz = tail call i33 @llvm.ctlz.i33(i33 %x, i1 true)
+  %trunc = trunc i33 %lz to i5
+  %cmp = icmp ugt i5 %trunc, 4
+  ret i1 %cmp
+}
+
+define i1 @trunc_ctlz_true_ugt_other_i32_i5(i32 %x) {
+; CHECK-LABEL: @trunc_ctlz_true_ugt_other_i32_i5(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[X:%.*]], 134217728
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %lz = tail call i32 @llvm.ctlz.i32(i32 %x, i1 true)
+  %trunc = trunc i32 %lz to i5
+  %cmp = icmp ugt i5 %trunc, 4
+  ret i1 %cmp
+}
+
+; negative case, is_zero_poison == false && log2(src bitwidth) == dest bitwidth
+
+define i1 @trunc_ctlz_false_ugt_other_i32_i5(i32 %x) {
+; CHECK-LABEL: @trunc_ctlz_false_ugt_other_i32_i5(
 ; CHECK-NEXT:    [[LZ:%.*]] = tail call i32 @llvm.ctlz.i32(i32 [[X:%.*]], i1 false), !range [[RNG0]]
-; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i32 [[LZ]] to i15
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i15 [[TRUNC]], 4
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i32 [[LZ]] to i5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i5 [[TRUNC]], 4
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %lz = tail call i32 @llvm.ctlz.i32(i32 %x, i1 false)
-  %trunc = trunc i32 %lz to i15
-  %cmp = icmp ugt i15 %trunc, 4
+  %trunc = trunc i32 %lz to i5
+  %cmp = icmp ugt i5 %trunc, 4
+  ret i1 %cmp
+}
+
+define i1 @trunc_ctlz_false_ugt_other_i32_i6(i32 %x) {
+; CHECK-LABEL: @trunc_ctlz_false_ugt_other_i32_i6(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[X:%.*]], 134217728
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %lz = tail call i32 @llvm.ctlz.i32(i32 %x, i1 false)
+  %trunc = trunc i32 %lz to i6
+  %cmp = icmp ugt i6 %trunc, 4
+  ret i1 %cmp
+}
+
+; negative case, trunc is not one use
+
+define i1 @trunc_ctlz_false_ugt_other_i32_i6_extra_use(i32 %x) {
+; CHECK-LABEL: @trunc_ctlz_false_ugt_other_i32_i6_extra_use(
+; CHECK-NEXT:    [[LZ:%.*]] = tail call i32 @llvm.ctlz.i32(i32 [[X:%.*]], i1 false), !range [[RNG0]]
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i32 [[LZ]] to i6
+; CHECK-NEXT:    call void @use6(i6 [[TRUNC]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i6 [[TRUNC]], 4
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %lz = tail call i32 @llvm.ctlz.i32(i32 %x, i1 false)
+  %trunc = trunc i32 %lz to i6
+  call void @use6(i6 %trunc)
+  %cmp = icmp ugt i6 %trunc, 4
   ret i1 %cmp
 }