diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 74df67a4ff9b4..c0104d2bc2611 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1677,6 +1677,8 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
     return Name == "fabs" || Name == "fabsf" ||
            Name == "floor" || Name == "floorf" ||
            Name == "fmod" || Name == "fmodf";
+  case 'i':
+    return Name == "ilogb" || Name == "ilogbf";
   case 'l':
     return Name == "log" || Name == "logf" || Name == "logl" ||
            Name == "log2" || Name == "log2f" || Name == "log10" ||
@@ -2131,7 +2133,8 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
     }
 #endif
 
-    if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy())
+    if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy() &&
+        !Ty->isIntegerTy())
       return nullptr;
 
     // Use internal versions of these intrinsics.
@@ -2391,6 +2394,11 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
         // TODO: What about hosts that lack a C99 library?
         return ConstantFoldFP(log10, APF, Ty);
       break;
+    case LibFunc_ilogb:
+    case LibFunc_ilogbf:
+      if (!APF.isZero() && TLI->has(Func))
+        return ConstantInt::get(Ty, ilogb(APF), true);
+      break;
     case LibFunc_logb:
     case LibFunc_logbf:
       if (!APF.isZero() && TLI->has(Func))
diff --git a/llvm/test/Transforms/InstCombine/ilogb.ll b/llvm/test/Transforms/InstCombine/ilogb.ll
new file mode 100644
index 0000000000000..e30791fe68e7b
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/ilogb.ll
@@ -0,0 +1,203 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define i32 @ilogbf_const1() {
+; CHECK-LABEL: define i32 @ilogbf_const1() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 7.000000e+00)
+; CHECK-NEXT:    ret i32 2
+;
+  %r = call i32 @ilogbf(float 7.000000e+00)
+  ret i32 %r
+}
+
+define i32 @ilogb_const1() {
+; CHECK-LABEL: define i32 @ilogb_const1() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double -7.000000e+00)
+; CHECK-NEXT:    ret i32 2
+;
+  %r = call i32 @ilogb(double -7.000000e+00)
+  ret i32 %r
+}
+
+define i32 @ilogbf_const2() {
+; CHECK-LABEL: define i32 @ilogbf_const2() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 5.000000e-01)
+; CHECK-NEXT:    ret i32 -1
+;
+  %r = call i32 @ilogbf(float 5.000000e-01)
+  ret i32 %r
+}
+
+define i32 @ilogb_const2() {
+; CHECK-LABEL: define i32 @ilogb_const2() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double -5.000000e-01)
+; CHECK-NEXT:    ret i32 -1
+;
+  %r = call i32 @ilogb(double -5.000000e-01)
+  ret i32 %r
+}
+
+define i32 @ilogbf_zero() {
+; CHECK-LABEL: define i32 @ilogbf_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 0.000000e+00)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float 0.000000e+00)
+  ret i32 %r
+}
+
+define i32 @ilogb_zero() {
+; CHECK-LABEL: define i32 @ilogb_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double 0.000000e+00)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double 0.000000e+00)
+  ret i32 %r
+}
+
+define i32 @ilogbf_neg_zero() {
+; CHECK-LABEL: define i32 @ilogbf_neg_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float -0.000000e+00)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float -0.000000e+00)
+  ret i32 %r
+}
+
+define i32 @ilogb_neg_zero() {
+; CHECK-LABEL: define i32 @ilogb_neg_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double -0.000000e+00)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double -0.000000e+00)
+  ret i32 %r
+}
+
+define i32 @ilogbf_inf() {
+; CHECK-LABEL: define i32 @ilogbf_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 0x7FF0000000000000)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float 0x7FF0000000000000)
+  ret i32 %r
+}
+
+define i32 @ilogb_inf() {
+; CHECK-LABEL: define i32 @ilogb_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double 0x7FF0000000000000)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double 0x7FF0000000000000)
+  ret i32 %r
+}
+
+define i32 @ilogbf_nan() {
+; CHECK-LABEL: define i32 @ilogbf_nan() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 0x7FF8000000000000)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float 0x7FF8000000000000)
+  ret i32 %r
+}
+
+define i32 @ilogb_nan() {
+; CHECK-LABEL: define i32 @ilogb_nan() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double 0x7FF8000000000000)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double 0x7FF8000000000000)
+  ret i32 %r
+}
+
+define i32 @ilogbf_zero_readnone() {
+; CHECK-LABEL: define i32 @ilogbf_zero_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 0.000000e+00) #[[ATTR0:[0-9]+]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float 0.000000e+00) readnone
+  ret i32 %r
+}
+
+define i32 @ilogb_zero_readnone() {
+; CHECK-LABEL: define i32 @ilogb_zero_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double 0.000000e+00) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double 0.000000e+00) readnone
+  ret i32 %r
+}
+
+define i32 @ilogbf_neg_zero_readnone() {
+; CHECK-LABEL: define i32 @ilogbf_neg_zero_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float -0.000000e+00) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float -0.000000e+00) readnone
+  ret i32 %r
+}
+
+define i32 @ilogb_neg_zero_readnone() {
+; CHECK-LABEL: define i32 @ilogb_neg_zero_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double -0.000000e+00) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double -0.000000e+00) readnone
+  ret i32 %r
+}
+
+define i32 @ilogbf_inf_readnone() {
+; CHECK-LABEL: define i32 @ilogbf_inf_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 0x7FF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float 0x7FF0000000000000) readnone
+  ret i32 %r
+}
+
+define i32 @ilogb_inf_readnone() {
+; CHECK-LABEL: define i32 @ilogb_inf_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double 0x7FF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double 0x7FF0000000000000) readnone
+  ret i32 %r
+}
+
+define i32 @ilogbf_nan_readnone() {
+; CHECK-LABEL: define i32 @ilogbf_nan_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float 0x7FF8000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float 0x7FF8000000000000) readnone
+  ret i32 %r
+}
+
+define i32 @ilogb_nan_readnone() {
+; CHECK-LABEL: define i32 @ilogb_nan_readnone() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double 0x7FF8000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double 0x7FF8000000000000) readnone
+  ret i32 %r
+}
+
+define i32 @ilogbf_poison() {
+; CHECK-LABEL: define i32 @ilogbf_poison() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogbf(float poison)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogbf(float poison)
+  ret i32 %r
+}
+
+define i32 @ilogb_poison() {
+; CHECK-LABEL: define i32 @ilogb_poison() {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @ilogb(double poison)
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %r = call i32 @ilogb(double poison)
+  ret i32 %r
+}
+
+declare i32 @ilogbf(float)
+declare i32 @ilogb(double)