[libc] Fix _Float16 detection for x86 (#73947)

Author: gchatelet

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

@@ -31,5 +31,6 @@ add_header_library(
   DEPENDS
     .architectures
     .compiler
+    .cpu_features
     .os
 )

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

@@ -13,6 +13,7 @@
 
 #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
@@ -30,7 +31,7 @@
 #endif
 
 // float16 support.
-#if defined(LIBC_TARGET_ARCH_IS_X86_64)
+#if defined(LIBC_TARGET_ARCH_IS_X86_64) && defined(LIBC_TARGET_CPU_HAS_SSE2)
 #if (defined(LIBC_COMPILER_CLANG_VER) && (LIBC_COMPILER_CLANG_VER >= 1500)) || \
     (defined(LIBC_COMPILER_GCC_VER) && (LIBC_COMPILER_GCC_VER >= 1201))
 #define LIBC_COMPILER_HAS_C23_FLOAT16

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

@@ -86,6 +86,7 @@ libc_support_library(
     deps = [
         ":__support_macros_properties_architectures",
         ":__support_macros_properties_compiler",
+        ":__support_macros_properties_cpu_features",
         ":__support_macros_properties_os",
     ],
 )