diff --git a/libc/src/__support/CMakeLists.txt b/libc/src/__support/CMakeLists.txt
--- a/libc/src/__support/CMakeLists.txt
+++ b/libc/src/__support/CMakeLists.txt
@@ -13,12 +13,17 @@
 )
 
 add_header_library(
-  builtin_wrappers
+  compiler_features
   HDRS
-    builtin_wrappers.h
+    compiler_features.h
+)
+
+add_header_library(
+  sanitizer
+  HDRS
+    sanitizer.h
   DEPENDS
-    .named_pair
-    libc.src.__support.CPP.type_traits
+    libc.src.__support.compiler_features
 )
 
 add_header_library(
@@ -27,7 +32,17 @@
     architectures.h
     common.h
     endian.h
-    sanitizer.h
+)
+
+add_header_library(
+  builtin_wrappers
+  HDRS
+    builtin_wrappers.h
+  DEPENDS
+    .named_pair
+    libc.src.__support.common
+    libc.src.__support.compiler_features
+    libc.src.__support.CPP.type_traits
 )
 
 add_header_library(
diff --git a/libc/src/__support/CPP/CMakeLists.txt b/libc/src/__support/CPP/CMakeLists.txt
--- a/libc/src/__support/CPP/CMakeLists.txt
+++ b/libc/src/__support/CPP/CMakeLists.txt
@@ -8,6 +8,8 @@
   bit
   HDRS
     bit.h
+  DEPENDS
+    libc.src.__support.compiler_features
 )
 
 add_header_library(
diff --git a/libc/src/__support/CPP/bit.h b/libc/src/__support/CPP/bit.h
--- a/libc/src/__support/CPP/bit.h
+++ b/libc/src/__support/CPP/bit.h
@@ -9,19 +9,17 @@
 #ifndef LLVM_LIBC_SUPPORT_CPP_BIT_H
 #define LLVM_LIBC_SUPPORT_CPP_BIT_H
 
+#include "src/__support/compiler_features.h"
+
 namespace __llvm_libc::cpp {
 
-#if defined __has_builtin
-#if __has_builtin(__builtin_bit_cast)
+#if LLVM_LIBC_HAS_BUILTIN(__builtin_bit_cast)
 #define LLVM_LIBC_HAS_BUILTIN_BIT_CAST
 #endif
-#endif
 
-#if defined __has_builtin
-#if __has_builtin(__builtin_memcpy_inline)
+#if LLVM_LIBC_HAS_BUILTIN(__builtin_memcpy_inline)
 #define LLVM_LIBC_HAS_BUILTIN_MEMCPY_INLINE
 #endif
-#endif
 
 // This function guarantees the bitcast to be optimized away by the compiler for
 // GCC >= 8 and Clang >= 6.
diff --git a/libc/src/__support/FPUtil/CMakeLists.txt b/libc/src/__support/FPUtil/CMakeLists.txt
--- a/libc/src/__support/FPUtil/CMakeLists.txt
+++ b/libc/src/__support/FPUtil/CMakeLists.txt
@@ -5,6 +5,7 @@
   DEPENDS
     libc.include.fenv
     libc.src.__support.common
+    libc.src.__support.compiler_features
 )
 
 add_header_library(
diff --git a/libc/src/__support/builtin_wrappers.h b/libc/src/__support/builtin_wrappers.h
--- a/libc/src/__support/builtin_wrappers.h
+++ b/libc/src/__support/builtin_wrappers.h
@@ -12,6 +12,7 @@
 
 #include "named_pair.h"
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/compiler_features.h"
 
 namespace __llvm_libc {
 
@@ -80,7 +81,7 @@
   return {sum, carry_out};
 }
 
-#if __has_builtin(__builtin_addc)
+#if LLVM_LIBC_HAS_BUILTIN(__builtin_addc)
 // https://clang.llvm.org/docs/LanguageExtensions.html#multiprecision-arithmetic-builtins
 
 template <>
@@ -128,7 +129,7 @@
   return result;
 }
 
-#endif // __has_builtin(__builtin_addc)
+#endif // LLVM_LIBC_HAS_BUILTIN(__builtin_addc)
 
 // Subtract with borrow
 DEFINE_NAMED_PAIR_TEMPLATE(DiffBorrow, diff, borrow);
@@ -143,7 +144,7 @@
   return {diff, borrow_out};
 }
 
-#if __has_builtin(__builtin_subc)
+#if LLVM_LIBC_HAS_BUILTIN(__builtin_subc)
 // https://clang.llvm.org/docs/LanguageExtensions.html#multiprecision-arithmetic-builtins
 
 template <>
@@ -191,7 +192,7 @@
   return result;
 }
 
-#endif // __has_builtin(__builtin_subc)
+#endif // LLVM_LIBC_HAS_BUILTIN(__builtin_subc)
 
 } // namespace __llvm_libc
 
diff --git a/libc/src/__support/compiler_features.h b/libc/src/__support/compiler_features.h
new file mode 100644
--- /dev/null
+++ b/libc/src/__support/compiler_features.h
@@ -0,0 +1,41 @@
+//===-- Compile time compiler detection -------------------------*- 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_SUPPORT_COMPILER_FEATURES_H
+#define LLVM_LIBC_SUPPORT_COMPILER_FEATURES_H
+
+#if defined(__clang__)
+#define LLVM_LIBC_COMPILER_CLANG
+#endif
+
+#if defined(__GNUC__) && !defined(__clang__)
+#define LLVM_LIBC_COMPILER_GCC
+#endif
+
+#if defined(_MSC_VER)
+#define LLVM_LIBC_COMPILER_MSC
+#endif
+
+// Compiler builtin-detection.
+// clang.llvm.org/docs/LanguageExtensions.html#has-builtin
+#if defined(LLVM_LIBC_COMPILER_CLANG) ||                                       \
+    (defined(LLVM_LIBC_COMPILER_GCC) && (__GNUC__ >= 10))
+#define LLVM_LIBC_HAS_BUILTIN(BUILTIN) __has_builtin(BUILTIN)
+#else
+#define LLVM_LIBC_HAS_BUILTIN(BUILTIN) 0
+#endif
+
+// Compiler feature-detection.
+// clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension
+#if defined(LLVM_LIBC_COMPILER_CLANG)
+#define LLVM_LIBC_HAS_FEATURE(FEATURE) __has_feature(FEATURE)
+#else
+#define LLVM_LIBC_HAS_FEATURE(FEATURE) 0
+#endif
+
+#endif // LLVM_LIBC_SUPPORT_COMPILER_FEATURES_H
diff --git a/libc/src/__support/sanitizer.h b/libc/src/__support/sanitizer.h
--- a/libc/src/__support/sanitizer.h
+++ b/libc/src/__support/sanitizer.h
@@ -9,11 +9,7 @@
 #ifndef LLVM_LIBC_SRC_SUPPORT_SANITIZER_H
 #define LLVM_LIBC_SRC_SUPPORT_SANITIZER_H
 
-#ifdef __has_feature
-#define LLVM_LIBC_HAVE_FEATURE(f) __has_feature(f)
-#else
-#define LLVM_LIBC_HAVE_FEATURE(f) 0
-#endif
+#include "src/__support/compiler_features.h"
 
 // MemorySanitizer (MSan) is a detector of uninitialized reads. It consists of
 // a compiler instrumentation module and a run-time library.
@@ -25,7 +21,7 @@
 #define LLVM_LIBC_HAVE_MEMORY_SANITIZER 1
 #elif defined(__SANITIZE_MEMORY__)
 #define LLVM_LIBC_HAVE_MEMORY_SANITIZER 1
-#elif !defined(__native_client__) && LLVM_LIBC_HAVE_FEATURE(memory_sanitizer)
+#elif !defined(__native_client__) && LLVM_LIBC_HAS_FEATURE(memory_sanitizer)
 #define LLVM_LIBC_HAVE_MEMORY_SANITIZER 1
 #endif
 
@@ -38,14 +34,14 @@
 #define LLVM_LIBC_HAVE_ADDRESS_SANITIZER 1
 #elif defined(__SANITIZE_ADDRESS__)
 #define LLVM_LIBC_HAVE_ADDRESS_SANITIZER 1
-#elif LLVM_LIBC_HAVE_FEATURE(address_sanitizer)
+#elif LLVM_LIBC_HAS_FEATURE(address_sanitizer)
 #define LLVM_LIBC_HAVE_ADDRESS_SANITIZER 1
 #endif
 
 // HWAddressSanitizer (HWASan) is a fast, low memory overhead error detector.
 #ifdef LLVM_LIBC_HAVE_HWADDRESS_SANITIZER
 #error "LLVM_LIBC_HAVE_HWADDRESS_SANITIZER cannot be directly set."
-#elif LLVM_LIBC_HAVE_FEATURE(hwaddress_sanitizer)
+#elif LLVM_LIBC_HAS_FEATURE(hwaddress_sanitizer)
 #define LLVM_LIBC_HAVE_HWADDRESS_SANITIZER 1
 #endif
 
diff --git a/libc/src/string/memory_utils/CMakeLists.txt b/libc/src/string/memory_utils/CMakeLists.txt
--- a/libc/src/string/memory_utils/CMakeLists.txt
+++ b/libc/src/string/memory_utils/CMakeLists.txt
@@ -15,6 +15,7 @@
     utils.h
   DEPS
     libc.src.__support.common
+    libc.src.__support.compiler_features
     libc.src.__support.CPP.bit
     libc.src.__support.CPP.cstddef
     libc.src.__support.CPP.type_traits
diff --git a/libc/src/string/memory_utils/utils.h b/libc/src/string/memory_utils/utils.h
--- a/libc/src/string/memory_utils/utils.h
+++ b/libc/src/string/memory_utils/utils.h
@@ -12,6 +12,7 @@
 #include "src/__support/CPP/bit.h"
 #include "src/__support/CPP/cstddef.h"
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/compiler_features.h"
 
 #include <stddef.h> // size_t
 #include <stdint.h> // intptr_t / uintptr_t
@@ -80,17 +81,13 @@
   return reinterpret_cast<T *>(__builtin_assume_aligned(ptr, alignment));
 }
 
-#if defined __has_builtin
-#if __has_builtin(__builtin_memcpy_inline)
+#if LLVM_LIBC_HAS_BUILTIN(__builtin_memcpy_inline)
 #define LLVM_LIBC_HAS_BUILTIN_MEMCPY_INLINE
 #endif
-#endif
 
-#if defined __has_builtin
-#if __has_builtin(__builtin_memset_inline)
+#if LLVM_LIBC_HAS_BUILTIN(__builtin_memset_inline)
 #define LLVM_LIBC_HAS_BUILTIN_MEMSET_INLINE
 #endif
-#endif
 
 // Performs a constant count copy.
 template <size_t Size>
diff --git a/libc/src/string/stpcpy.cpp b/libc/src/string/stpcpy.cpp
--- a/libc/src/string/stpcpy.cpp
+++ b/libc/src/string/stpcpy.cpp
@@ -11,7 +11,6 @@
 #include "src/string/string_utils.h"
 
 #include "src/__support/common.h"
-#include "src/__support/sanitizer.h"
 
 namespace __llvm_libc {
 
diff --git a/libc/test/src/string/memory_utils/CMakeLists.txt b/libc/test/src/string/memory_utils/CMakeLists.txt
--- a/libc/test/src/string/memory_utils/CMakeLists.txt
+++ b/libc/test/src/string/memory_utils/CMakeLists.txt
@@ -9,8 +9,9 @@
     ${LIBC_COMPILE_OPTIONS_NATIVE}
     -ffreestanding
   DEPENDS
-    libc.src.string.memory_utils.memory_utils
+    libc.src.__support.compiler_features
     libc.src.__support.CPP.array
-    libc.src.__support.CPP.span
     libc.src.__support.CPP.cstddef
+    libc.src.__support.CPP.span
+    libc.src.string.memory_utils.memory_utils
 )
diff --git a/libc/test/src/string/memory_utils/memory_check_utils.h b/libc/test/src/string/memory_utils/memory_check_utils.h
--- a/libc/test/src/string/memory_utils/memory_check_utils.h
+++ b/libc/test/src/string/memory_utils/memory_check_utils.h
@@ -10,13 +10,14 @@
 #define LIBC_TEST_SRC_STRING_MEMORY_UTILS_MEMORY_CHECK_UTILS_H
 
 #include "src/__support/CPP/span.h"
+#include "src/__support/compiler_features.h"
 #include "src/string/memory_utils/utils.h"
 #include <assert.h> // assert
 #include <stddef.h> // size_t
 #include <stdint.h> // uintxx_t
 #include <stdlib.h> // malloc/free
 
-#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+#if LLVM_LIBC_HAS_FEATURE(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
 #include <sanitizer/asan_interface.h>
 #define ASAN_POISON_MEMORY_REGION(addr, size)                                  \
   __asan_poison_memory_region((addr), (size))
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -60,13 +60,23 @@
 
 ############################## Support libraries #############################
 
+libc_support_library(
+    name = "__support_compiler_features",
+    hdrs = ["src/__support/compiler_features.h"],
+)
+
+libc_support_library(
+    name = "__support_sanitizer",
+    hdrs = ["src/__support/sanitizer.h"],
+    deps = [":__support_compiler_features"],
+)
+
 libc_support_library(
     name = "__support_common",
     hdrs = [
         "src/__support/architectures.h",
         "src/__support/common.h",
         "src/__support/endian.h",
-        "src/__support/sanitizer.h",
     ],
 )
 
@@ -79,7 +89,10 @@
 libc_support_library(
     name = "__support_cpp_bit",
     hdrs = ["src/__support/CPP/bit.h"],
-    deps = [":libc_root"],
+    deps = [
+        ":__support_compiler_features",
+        ":libc_root",
+    ],
 )
 
 libc_support_library(
@@ -255,6 +268,7 @@
     name = "__support_builtin_wrappers",
     hdrs = ["src/__support/builtin_wrappers.h"],
     deps = [
+        ":__support_common",
         ":__support_cpp_type_traits",
         ":__support_named_pair",
         ":libc_root",
@@ -294,7 +308,9 @@
     ],
     deps = [
         ":__support_common",
+        ":__support_compiler_features",
         ":__support_fputil_fp_bits",
+        ":__support_sanitizer",
         ":libc_root",
     ],
 )