[libc] Fix generated float128 header for aarch64 target. (#78017)

Author: lntue

libc/config/linux/aarch64/entrypoints.txt

@@ -379,8 +379,7 @@ set(TARGET_LIBM_ENTRYPOINTS
 if(LIBC_COMPILER_HAS_FLOAT128)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # math.h C23 _Float128 entrypoints
-    # Temporarily disabled since float128 isn't working on the aarch64 buildbot
-    # libc.src.math.fabsf128
+    libc.src.math.fabsf128
   )
 endif()
 

libc/config/linux/api.td

@@ -55,7 +55,7 @@ def IntTypesAPI : PublicAPI<"inttypes.h"> {
 }
 
 def MathAPI : PublicAPI<"math.h"> {
-  let Types = ["double_t", "float_t"];
+  let Types = ["double_t", "float_t", "float128"];
 }
 
 def FenvAPI: PublicAPI<"fenv.h"> {

libc/include/CMakeLists.txt

@@ -100,6 +100,7 @@ add_gen_header(
     .llvm-libc-macros.math_macros
     .llvm-libc-types.double_t
     .llvm-libc-types.float_t
+    .llvm-libc-types.float128
 )
 
 # TODO: This should be conditional on POSIX networking being included.

libc/include/llvm-libc-types/CMakeLists.txt

@@ -98,3 +98,10 @@ add_header(ENTRY HDR ENTRY.h)
 add_header(struct_hsearch_data HDR struct_hsearch_data.h)
 add_header(struct_epoll_event HDR struct_epoll_event.h)
 add_header(struct_epoll_data HDR struct_epoll_data.h)
+add_header(
+  float128
+  HDR
+    float128.h
+  DEPENDS
+    libc.include.llvm-libc-macros.float_macros
+)

libc/include/llvm-libc-types/float128.h

@@ -0,0 +1,37 @@
+//===-- Definition of float128 type ---------------------------------------===//
+//
+// 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_TYPES_FLOAT128_H__
+#define __LLVM_LIBC_TYPES_FLOAT128_H__
+
+#include <include/llvm-libc-macros/float-macros.h> // LDBL_MANT_DIG
+
+// Currently, C23 `_Float128` type is only defined as a built-in type in GCC 7
+// or later, and only for C.  For C++, or for clang, `__float128` is defined
+// instead, and only on x86-64 targets.
+//
+// TODO: Update C23 `_Float128` type detection again when clang supports it.
+//   https://github.com/llvm/llvm-project/issues/80195
+#if defined(__STDC_IEC_60559_BFP__) && !defined(__clang__) &&                  \
+    !defined(__cplusplus)
+// Use _Float128 C23 type.
+#define LIBC_COMPILER_HAS_C23_FLOAT128
+typedef _Float128 float128;
+#elif defined(__FLOAT128__) || defined(__SIZEOF_FLOAT128__)
+// Use __float128 type.  gcc and clang sometime use __SIZEOF_FLOAT128__ to
+// notify the availability of __float128.
+// clang also uses __FLOAT128__ macro to notify the availability of __float128
+// type: https://reviews.llvm.org/D15120
+#define LIBC_COMPILER_HAS_FLOAT128_EXTENSION
+typedef __float128 float128;
+#elif (LDBL_MANT_DIG == 113)
+// Use long double.
+typedef long double float128;
+#endif
+
+#endif // __LLVM_LIBC_TYPES_FLOAT128_H__

libc/spec/spec.td

@@ -53,7 +53,7 @@ def UnsignedCharType : NamedType<"unsigned char">;
 def UnsignedShortType : NamedType<"unsigned short">;
 
 // TODO: Add compatibility layer to use C23 type _Float128 if possible.
-def Float128Type : NamedType<"__float128">;
+def Float128Type : NamedType<"float128">;
 
 // Common types
 def VoidPtr : PtrType<VoidType>;

libc/spec/stdc.td

@@ -352,6 +352,7 @@ def StdC : StandardSpec<"stdc"> {
       [
           NamedType<"float_t">,
           NamedType<"double_t">,
+          NamedType<"float128">,
       ],
       [], // Enumerations
       [

libc/src/__support/FPUtil/generic/sqrt.h

@@ -36,8 +36,9 @@ template <> struct SpecialLongDouble<long double> {
 template <typename T>
 LIBC_INLINE void normalize(int &exponent,
                            typename FPBits<T>::StorageType &mantissa) {
-  const int shift = cpp::countl_zero(mantissa) -
-                    (8 * sizeof(mantissa) - 1 - FPBits<T>::FRACTION_LEN);
+  const int shift =
+      cpp::countl_zero(mantissa) -
+      (8 * static_cast<int>(sizeof(mantissa)) - 1 - FPBits<T>::FRACTION_LEN);
   exponent -= shift;
   mantissa <<= shift;
 }

libc/src/__support/macros/properties/CMakeLists.txt

@@ -33,4 +33,6 @@ add_header_library(
     .compiler
     .cpu_features
     .os
+    libc.include.llvm-libc-macros.float_macros
+    libc.include.llvm-libc-types.float128
 )

libc/src/__support/macros/properties/float.h

@@ -11,13 +11,13 @@
 #ifndef LLVM_LIBC_SRC___SUPPORT_MACROS_PROPERTIES_FLOAT_H
 #define LLVM_LIBC_SRC___SUPPORT_MACROS_PROPERTIES_FLOAT_H
 
+#include "include/llvm-libc-macros/float-macros.h" // LDBL_MANT_DIG
+#include "include/llvm-libc-types/float128.h"      // float128
 #include "src/__support/macros/properties/architectures.h"
 #include "src/__support/macros/properties/compiler.h"
 #include "src/__support/macros/properties/cpu_features.h"
 #include "src/__support/macros/properties/os.h"
 
-#include <float.h> // LDBL_MANT_DIG
-
 // 'long double' properties.
 #if (LDBL_MANT_DIG == 53)
 #define LIBC_LONG_DOUBLE_IS_FLOAT64
@@ -53,26 +53,6 @@ using float16 = _Float16;
 #endif
 
 // float128 support.
-#if (defined(LIBC_COMPILER_GCC_VER) && (LIBC_COMPILER_GCC_VER >= 1301)) &&     \
-    (defined(LIBC_TARGET_ARCH_IS_AARCH64) ||                                   \
-     defined(LIBC_TARGET_ARCH_IS_ANY_RISCV) ||                                 \
-     defined(LIBC_TARGET_ARCH_IS_X86_64))
-#define LIBC_COMPILER_HAS_C23_FLOAT128
-#endif
-#if (defined(LIBC_COMPILER_CLANG_VER) && (LIBC_COMPILER_CLANG_VER >= 600)) &&  \
-    (defined(LIBC_TARGET_ARCH_IS_X86_64) &&                                    \
-     defined(LIBC_TARGET_OS_IS_LINUX) && !defined(LIBC_TARGET_OS_IS_FUCHSIA))
-#define LIBC_COMPILER_HAS_FLOAT128_EXTENSION
-#endif
-
-#if defined(LIBC_COMPILER_HAS_C23_FLOAT128)
-using float128 = _Float128;
-#elif defined(LIBC_COMPILER_HAS_FLOAT128_EXTENSION)
-using float128 = __float128;
-#elif defined(LIBC_LONG_DOUBLE_IS_FLOAT128)
-using float128 = long double;
-#endif
-
 #if defined(LIBC_COMPILER_HAS_C23_FLOAT128) ||                                 \
     defined(LIBC_COMPILER_HAS_FLOAT128_EXTENSION) ||                           \
     defined(LIBC_LONG_DOUBLE_IS_FLOAT128)