[libc][math][c23] Add ilogbf16 C23 math function

Author: overmighty

libc/config/linux/aarch64/entrypoints.txt

@@ -518,6 +518,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.frexpf16
     libc.src.math.fromfpf16
     libc.src.math.fromfpxf16
+    libc.src.math.ilogbf16
     libc.src.math.llrintf16
     libc.src.math.llroundf16
     libc.src.math.lrintf16

libc/config/linux/x86_64/entrypoints.txt

@@ -550,6 +550,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.frexpf16
     libc.src.math.fromfpf16
     libc.src.math.fromfpxf16
+    libc.src.math.ilogbf16
     libc.src.math.llrintf16
     libc.src.math.llroundf16
     libc.src.math.lrintf16

libc/docs/math/index.rst

@@ -168,7 +168,7 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | fsub             | N/A              |                 |                        | N/A                  |                        | 7.12.14.2              | F.10.11                    |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| ilogb            | |check|          | |check|         | |check|                |                      | |check|                | 7.12.6.8               | F.10.3.8                   |
+| ilogb            | |check|          | |check|         | |check|                | |check|              | |check|                | 7.12.6.8               | F.10.3.8                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | ldexp            | |check|          | |check|         | |check|                |                      | |check|                | 7.12.6.9               | F.10.3.9                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

libc/spec/stdc.td

@@ -516,6 +516,7 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"ilogb", RetValSpec<IntType>, [ArgSpec<DoubleType>]>,
           FunctionSpec<"ilogbf", RetValSpec<IntType>, [ArgSpec<FloatType>]>,
           FunctionSpec<"ilogbl", RetValSpec<IntType>, [ArgSpec<LongDoubleType>]>,
+          GuardedFunctionSpec<"ilogbf16", RetValSpec<IntType>, [ArgSpec<Float16Type>], "LIBC_TYPES_HAS_FLOAT16">,
           GuardedFunctionSpec<"ilogbf128", RetValSpec<IntType>, [ArgSpec<Float128Type>], "LIBC_TYPES_HAS_FLOAT128">,
 
           FunctionSpec<"llogb", RetValSpec<LongType>, [ArgSpec<DoubleType>]>,

libc/src/__support/FPUtil/CMakeLists.txt

@@ -217,6 +217,7 @@ add_header_library(
     .nearest_integer_operations
     .normal_float
     libc.hdr.math_macros
+    libc.src.__support.CPP.algorithm
     libc.src.__support.CPP.bit
     libc.src.__support.CPP.limits
     libc.src.__support.CPP.type_traits

libc/src/__support/FPUtil/ManipulationFunctions.h

@@ -16,6 +16,7 @@
 #include "rounding_mode.h"
 
 #include "hdr/math_macros.h"
+#include "src/__support/CPP/algorithm.h"
 #include "src/__support/CPP/bit.h"
 #include "src/__support/CPP/limits.h" // INT_MAX, INT_MIN
 #include "src/__support/CPP/type_traits.h"
@@ -102,7 +103,7 @@ intlogb(U x) {
     return IntLogbConstants<T>::T_MAX;
   }
 
-  DyadicFloat<FPBits<U>::STORAGE_LEN> normal(bits.get_val());
+  DyadicFloat<cpp::max(FPBits<U>::STORAGE_LEN, 32)> normal(bits.get_val());
   int exponent = normal.get_unbiased_exponent();
   // The C standard does not specify the return value when an exponent is
   // out of int range. However, XSI conformance required that INT_MAX or

libc/src/math/CMakeLists.txt

@@ -209,6 +209,7 @@ add_math_entrypoint_object(hypotf)
 add_math_entrypoint_object(ilogb)
 add_math_entrypoint_object(ilogbf)
 add_math_entrypoint_object(ilogbl)
+add_math_entrypoint_object(ilogbf16)
 add_math_entrypoint_object(ilogbf128)
 
 add_math_entrypoint_object(llogb)

libc/src/math/generic/CMakeLists.txt

@@ -1363,6 +1363,19 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  ilogbf16
+  SRCS
+    ilogbf16.cpp
+  HDRS
+    ../ilogbf16.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.manipulation_functions
+)
+
 add_entrypoint_object(
   ilogbf128
   SRCS

libc/src/math/generic/ilogbf16.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of ilogbf16 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/ilogbf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, ilogbf16, (float16 x)) {
+  return fputil::intlogb<int>(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/ilogbf16.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for ilogbf16 ----------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_MATH_ILOGBF16_H
+#define LLVM_LIBC_SRC_MATH_ILOGBF16_H
+
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE {
+
+int ilogbf16(float16 x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_ILOGBF16_H