[libc] Provide isnan, isnanf and isnanl functions

While C99 defines type generic isnan macro, BSD provided isnan, isnanf
and isnanl in prior C standards and existing code still relies on these.

Author: petrhosek

libc/config/baremetal/arm/entrypoints.txt

@@ -273,6 +273,9 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.ilogb
     libc.src.math.ilogbf
     libc.src.math.ilogbl
+    libc.src.math.isnan
+    libc.src.math.isnanf
+    libc.src.math.isnanl
     libc.src.math.ldexp
     libc.src.math.ldexpf
     libc.src.math.ldexpl

libc/config/baremetal/riscv/entrypoints.txt

@@ -268,6 +268,9 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.ilogb
     libc.src.math.ilogbf
     libc.src.math.ilogbl
+    libc.src.math.isnan
+    libc.src.math.isnanf
+    libc.src.math.isnanl
     libc.src.math.ldexp
     libc.src.math.ldexpf
     libc.src.math.ldexpl

libc/include/llvm-libc-macros/math-macros.h

@@ -54,6 +54,5 @@
 // TODO: Move generic functional math macros to a separate header file.
 #define isfinite(x) __builtin_isfinite(x)
 #define isinf(x) __builtin_isinf(x)
-#define isnan(x) __builtin_isnan(x)
 
 #endif // LLVM_LIBC_MACROS_MATH_MACROS_H

libc/include/math.h.def

@@ -17,4 +17,6 @@
 
 %%public_api()
 
+#define isnan(x) __builtin_isnan(x)
+
 #endif // LLVM_LIBC_MATH_H

libc/spec/bsd_ext.td

@@ -1,4 +1,16 @@
 def BsdExtensions : StandardSpec<"BSDExtensions"> {
+  HeaderSpec Math = HeaderSpec<
+      "math.h",
+      [], // Macros
+      [], // Types
+      [], // Enumerations
+      [
+          FunctionSpec<"isnan", RetValSpec<IntType>, [ArgSpec<DoubleType>]>,
+          FunctionSpec<"isnanf", RetValSpec<IntType>, [ArgSpec<FloatType>]>,
+          FunctionSpec<"isnanl", RetValSpec<IntType>, [ArgSpec<LongDoubleType>]>,
+      ]
+  >;
+
   HeaderSpec String = HeaderSpec<
       "string.h",
       [], // Macros
@@ -67,6 +79,7 @@ def BsdExtensions : StandardSpec<"BSDExtensions"> {
   >;
 
   let Headers = [
+    Math,
     String,
     Strings,
     SysWait,

libc/src/math/CMakeLists.txt

@@ -223,6 +223,10 @@ add_math_entrypoint_object(ilogbl)
 add_math_entrypoint_object(ilogbf16)
 add_math_entrypoint_object(ilogbf128)
 
+add_math_entrypoint_object(isnan)
+add_math_entrypoint_object(isnanf)
+add_math_entrypoint_object(isnanl)
+
 add_math_entrypoint_object(llogb)
 add_math_entrypoint_object(llogbf)
 add_math_entrypoint_object(llogbl)

libc/src/math/generic/CMakeLists.txt

@@ -2791,6 +2791,36 @@ add_entrypoint_object(
     -O3
 )
 
+add_entrypoint_object(
+  isnan
+  SRCS
+    isnan.cpp
+  HDRS
+    ../isnan.h
+  COMPILE_OPTIONS
+    -O3
+)
+
+add_entrypoint_object(
+  isnanf
+  SRCS
+    isnanf.cpp
+  HDRS
+    ../isnanf.h
+  COMPILE_OPTIONS
+    -O3
+)
+
+add_entrypoint_object(
+  isnanl
+  SRCS
+    isnanl.cpp
+  HDRS
+    ../isnanl.h
+  COMPILE_OPTIONS
+    -O3
+)
+
 add_entrypoint_object(
   nan
   SRCS

libc/src/math/generic/isnan.cpp

@@ -0,0 +1,18 @@
+//===-- Implementation of isnan function ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/isnan.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, isnan, (double x)) {
+  return __builtin_isnan(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/generic/isnanf.cpp

@@ -0,0 +1,18 @@
+//===-- Implementation of isnanf function ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/isnanf.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, isnanf, (float x)) {
+  return __builtin_isnan(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/generic/isnanl.cpp

@@ -0,0 +1,18 @@
+//===-- Implementation of isnanl function ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/isnanl.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, isnanl, (long double x)) {
+  return __builtin_isnan(x);
+}
+
+} // namespace LIBC_NAMESPACE