diff --git a/flang/lib/Evaluate/fold-logical.cpp b/flang/lib/Evaluate/fold-logical.cpp
--- a/flang/lib/Evaluate/fold-logical.cpp
+++ b/flang/lib/Evaluate/fold-logical.cpp
@@ -108,6 +108,18 @@
     }
   } else if (name == "merge") {
     return FoldMerge<T>(context, std::move(funcRef));
+  } else if (name == "__builtin_ieee_support_datatype" ||
+      name == "__builtin_ieee_support_denormal" ||
+      name == "__builtin_ieee_support_divide" ||
+      name == "__builtin_ieee_support_divide" ||
+      name == "__builtin_ieee_support_inf" ||
+      name == "__builtin_ieee_support_io" ||
+      name == "__builtin_ieee_support_nan" ||
+      name == "__builtin_ieee_support_sqrt" ||
+      name == "__builtin_ieee_support_standard" ||
+      name == "__builtin_ieee_support_subnormal" ||
+      name == "__builtin_ieee_support_underflow_control") {
+    return Expr<T>{true};
   }
   // TODO: btest, cshift, dot_product, eoshift, is_iostat_end,
   // is_iostat_eor, lge, lgt, lle, llt, logical, matmul, out_of_range,
diff --git a/flang/lib/Evaluate/intrinsics.cpp b/flang/lib/Evaluate/intrinsics.cpp
--- a/flang/lib/Evaluate/intrinsics.cpp
+++ b/flang/lib/Evaluate/intrinsics.cpp
@@ -772,6 +772,36 @@
             {"back", AnyLogical, Rank::elemental, Optionality::optional},
             DefaultingKIND},
         KINDInt},
+    {"__builtin_ieee_support_datatype",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_denormal",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_divide",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_inf",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_io",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_nan",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_sqrt",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_standard",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_subnormal",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
+    {"__builtin_ieee_support_underflow_control",
+        {{"x", AnyReal, Rank::elemental, Optionality::optional}},
+        DefaultLogical},
 };
 
 // TODO: Coarray intrinsic functions
diff --git a/flang/module/__fortran_builtins.f90 b/flang/module/__fortran_builtins.f90
--- a/flang/module/__fortran_builtins.f90
+++ b/flang/module/__fortran_builtins.f90
@@ -31,4 +31,11 @@
   end type
 
   procedure(type(__builtin_c_ptr)) :: __builtin_c_loc
+
+  intrinsic :: __builtin_ieee_support_datatype, &
+    __builtin_ieee_support_denormal, __builtin_ieee_support_divide, &
+    __builtin_ieee_support_inf, __builtin_ieee_support_io, &
+    __builtin_ieee_support_nan, __builtin_ieee_support_sqrt, &
+    __builtin_ieee_support_standard, __builtin_ieee_support_subnormal, &
+    __builtin_ieee_support_underflow_control
 end module
diff --git a/flang/module/ieee_arithmetic.f90 b/flang/module/ieee_arithmetic.f90
--- a/flang/module/ieee_arithmetic.f90
+++ b/flang/module/ieee_arithmetic.f90
@@ -9,6 +9,18 @@
 ! See Fortran 2018, clause 17.2
 module ieee_arithmetic
 
+  use __Fortran_builtins, only: &
+    ieee_support_datatype => __builtin_ieee_support_datatype, &
+    ieee_support_denormal => __builtin_ieee_support_denormal, &
+    ieee_support_divide => __builtin_ieee_support_divide, &
+    ieee_support_inf => __builtin_ieee_support_inf, &
+    ieee_support_io => __builtin_ieee_support_io, &
+    ieee_support_nan => __builtin_ieee_support_nan, &
+    ieee_support_sqrt => __builtin_ieee_support_sqrt, &
+    ieee_support_standard => __builtin_ieee_support_standard, &
+    ieee_support_subnormal => __builtin_ieee_support_subnormal, &
+    ieee_support_underflow_control => __builtin_ieee_support_underflow_control
+
   type :: ieee_class_type
     private
     integer(kind=1) :: which = 0
@@ -72,6 +84,15 @@
     module procedure ieee_copy_sign_a16
   end interface ieee_copy_sign
 
+  generic :: ieee_support_rounding => ieee_support_rounding_, &
+    ieee_support_rounding_2, ieee_support_rounding_3, &
+    ieee_support_rounding_4, ieee_support_rounding_8, &
+    ieee_support_rounding_10, ieee_support_rounding_16
+  private :: ieee_support_rounding_, &
+    ieee_support_rounding_2, ieee_support_rounding_3, &
+    ieee_support_rounding_4, ieee_support_rounding_8, &
+    ieee_support_rounding_10, ieee_support_rounding_16
+
   ! TODO: more interfaces (_fma, &c.)
 
   private :: classify
@@ -181,4 +202,39 @@
   _COPYSIGN(16,16,128)
 #undef _COPYSIGN
 
+  pure logical function ieee_support_rounding_(round_type)
+    type(ieee_round_type), intent(in) :: round_type
+    ieee_support_rounding_ = .true.
+  end function
+  pure logical function ieee_support_rounding_2(round_type,x)
+    type(ieee_round_type), intent(in) :: round_type
+    real(kind=2), intent(in) :: x
+    ieee_support_rounding_2 = .true.
+  end function
+  pure logical function ieee_support_rounding_3(round_type,x)
+    type(ieee_round_type), intent(in) :: round_type
+    real(kind=3), intent(in) :: x
+    ieee_support_rounding_3 = .true.
+  end function
+  pure logical function ieee_support_rounding_4(round_type,x)
+    type(ieee_round_type), intent(in) :: round_type
+    real(kind=4), intent(in) :: x
+    ieee_support_rounding_4 = .true.
+  end function
+  pure logical function ieee_support_rounding_8(round_type,x)
+    type(ieee_round_type), intent(in) :: round_type
+    real(kind=8), intent(in) :: x
+    ieee_support_rounding_8 = .true.
+  end function
+  pure logical function ieee_support_rounding_10(round_type,x)
+    type(ieee_round_type), intent(in) :: round_type
+    real(kind=10), intent(in) :: x
+    ieee_support_rounding_10 = .true.
+  end function
+  pure logical function ieee_support_rounding_16(round_type,x)
+    type(ieee_round_type), intent(in) :: round_type
+    real(kind=16), intent(in) :: x
+    ieee_support_rounding_16 = .true.
+  end function
+
 end module ieee_arithmetic
diff --git a/flang/test/Evaluate/folding18.f90 b/flang/test/Evaluate/folding18.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Evaluate/folding18.f90
@@ -0,0 +1,75 @@
+! RUN: %S/test_folding.sh %s %t %f18
+! Test implementations of IEEE inquiry functions
+module m
+  use ieee_arithmetic
+  logical, parameter :: test_ieee_support_datatype = ieee_support_datatype() &
+    .and. ieee_support_datatype(1.0_2) &
+    .and. ieee_support_datatype(1.0_3) &
+    .and. ieee_support_datatype(1.0_4) &
+    .and. ieee_support_datatype(1.0_8) &
+    .and. ieee_support_datatype(1.0_10) &
+    .and. ieee_support_datatype(1.0_16)
+  logical, parameter :: test_ieee_support_denormal = ieee_support_denormal() &
+    .and. ieee_support_denormal(1.0_2) &
+    .and. ieee_support_denormal(1.0_3) &
+    .and. ieee_support_denormal(1.0_4) &
+    .and. ieee_support_denormal(1.0_8) &
+    .and. ieee_support_denormal(1.0_10) &
+    .and. ieee_support_denormal(1.0_16)
+  logical, parameter :: test_ieee_support_divide = ieee_support_divide() &
+    .and. ieee_support_divide(1.0_2) &
+    .and. ieee_support_divide(1.0_3) &
+    .and. ieee_support_divide(1.0_4) &
+    .and. ieee_support_divide(1.0_8) &
+    .and. ieee_support_divide(1.0_10) &
+    .and. ieee_support_divide(1.0_16)
+  logical, parameter :: test_ieee_support_inf = ieee_support_inf() &
+    .and. ieee_support_inf(1.0_2) &
+    .and. ieee_support_inf(1.0_3) &
+    .and. ieee_support_inf(1.0_4) &
+    .and. ieee_support_inf(1.0_8) &
+    .and. ieee_support_inf(1.0_10) &
+    .and. ieee_support_inf(1.0_16)
+  logical, parameter :: test_ieee_support_io = ieee_support_io() &
+    .and. ieee_support_io(1.0_2) &
+    .and. ieee_support_io(1.0_3) &
+    .and. ieee_support_io(1.0_4) &
+    .and. ieee_support_io(1.0_8) &
+    .and. ieee_support_io(1.0_10) &
+    .and. ieee_support_io(1.0_16)
+  logical, parameter :: test_ieee_support_nan = ieee_support_nan() &
+    .and. ieee_support_nan(1.0_2) &
+    .and. ieee_support_nan(1.0_3) &
+    .and. ieee_support_nan(1.0_4) &
+    .and. ieee_support_nan(1.0_8) &
+    .and. ieee_support_nan(1.0_10) &
+    .and. ieee_support_nan(1.0_16)
+  logical, parameter :: test_ieee_support_sqrt = ieee_support_sqrt() &
+    .and. ieee_support_sqrt(1.0_2) &
+    .and. ieee_support_sqrt(1.0_3) &
+    .and. ieee_support_sqrt(1.0_4) &
+    .and. ieee_support_sqrt(1.0_8) &
+    .and. ieee_support_sqrt(1.0_10) &
+    .and. ieee_support_sqrt(1.0_16)
+  logical, parameter :: test_ieee_support_standard = ieee_support_standard() &
+    .and. ieee_support_standard(1.0_2) &
+    .and. ieee_support_standard(1.0_3) &
+    .and. ieee_support_standard(1.0_4) &
+    .and. ieee_support_standard(1.0_8) &
+    .and. ieee_support_standard(1.0_10) &
+    .and. ieee_support_standard(1.0_16)
+  logical, parameter :: test_ieee_support_subnormal = ieee_support_subnormal() &
+    .and. ieee_support_subnormal(1.0_2) &
+    .and. ieee_support_subnormal(1.0_3) &
+    .and. ieee_support_subnormal(1.0_4) &
+    .and. ieee_support_subnormal(1.0_8) &
+    .and. ieee_support_subnormal(1.0_10) &
+    .and. ieee_support_subnormal(1.0_16)
+  logical, parameter :: test_ieee_support_underflow_control = ieee_support_underflow_control() &
+    .and. ieee_support_underflow_control(1.0_2) &
+    .and. ieee_support_underflow_control(1.0_3) &
+    .and. ieee_support_underflow_control(1.0_4) &
+    .and. ieee_support_underflow_control(1.0_8) &
+    .and. ieee_support_underflow_control(1.0_10) &
+    .and. ieee_support_underflow_control(1.0_16)
+end module