diff --git a/os/common/portability/CW/ccportab.h b/os/common/portability/CW/ccportab.h
index f6dc3cd1b..574a571b1 100644
--- a/os/common/portability/CW/ccportab.h
+++ b/os/common/portability/CW/ccportab.h
@@ -120,6 +120,20 @@
  *          compiler.
  */
 #define CC_ROMCONST         const
+
+/**
+ * @brief   Marks a boolean expression as likely true.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_LIKELY(x)        x
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_UNLIKELY(x)      x
 /** @} */
 
 /*===========================================================================*/
diff --git a/os/common/portability/GCC/ccportab.h b/os/common/portability/GCC/ccportab.h
index e0c8a1013..f4612ef55 100644
--- a/os/common/portability/GCC/ccportab.h
+++ b/os/common/portability/GCC/ccportab.h
@@ -120,6 +120,20 @@
  *          compiler.
  */
 #define CC_ROMCONST         const
+
+/**
+ * @brief   Marks a boolean expression as likely true.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_LIKELY(x)        __builtin_expect(!!(x), 1)
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_UNLIKELY(x)      __builtin_expect(!!(x), 0)
 /** @} */
 
 /*===========================================================================*/
diff --git a/os/common/portability/GHS/ccportab.h b/os/common/portability/GHS/ccportab.h
index d3aadf2ed..affde08f8 100644
--- a/os/common/portability/GHS/ccportab.h
+++ b/os/common/portability/GHS/ccportab.h
@@ -120,6 +120,20 @@
  *          compiler.
  */
 #define CC_ROMCONST         const
+
+/**
+ * @brief   Marks a boolean expression as likely true.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_LIKELY(x)        x
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_UNLIKELY(x)      x
 /** @} */
 
 /*===========================================================================*/
diff --git a/os/common/portability/IAR/ccportab.h b/os/common/portability/IAR/ccportab.h
index efccb7324..a1440e1c3 100644
--- a/os/common/portability/IAR/ccportab.h
+++ b/os/common/portability/IAR/ccportab.h
@@ -120,6 +120,20 @@
  *          compiler.
  */
 #define CC_ROMCONST         const
+
+/**
+ * @brief   Marks a boolean expression as likely true.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_LIKELY(x)        x
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_UNLIKELY(x)      x
 /** @} */
 
 /*===========================================================================*/
diff --git a/os/common/portability/Keil/ccportab.h b/os/common/portability/Keil/ccportab.h
index 5bc0faa75..13c41ab51 100644
--- a/os/common/portability/Keil/ccportab.h
+++ b/os/common/portability/Keil/ccportab.h
@@ -120,6 +120,20 @@
  *          compiler.
  */
 #define CC_ROMCONST         const
+
+/**
+ * @brief   Marks a boolean expression as likely true.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_LIKELY(x)        x
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ *
+ * @param[in] x         a valid expression
+ */
+#define CC_UNLIKELY(x)      x
 /** @} */
 
 /*===========================================================================*/
diff --git a/os/common/ports/ARM-common/chtypes.h b/os/common/ports/ARM-common/chtypes.h
index fc3f420ec..734819aca 100644
--- a/os/common/ports/ARM-common/chtypes.h
+++ b/os/common/ports/ARM-common/chtypes.h
@@ -101,6 +101,28 @@ typedef uint64_t            port_stkalign_t;
  */
 #define SIZEOF_PTR          PORT_ARCH_SIZEOF_DATA_PTR
 
+/**
+ * @brief   Marks a boolean expression as likely true.
+ *
+ * @param[in] x         a valid expression
+ */
+#if defined(CC_LIKELY) || defined(__DOXYGEN__)
+#define PORT_LIKELY(x)      CC_LIKELY(x)
+#else
+#define PORT_LIKELY(x)      x
+#endif
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ *
+ * @param[in] x         a valid expression
+ */
+#if defined(CC_UNLIKELY) || defined(__DOXYGEN__)
+#define PORT_UNLIKELY(x)    CC_UNLIKELY(x)
+#else
+#define PORT_UNLIKELY(x)    x
+#endif
+
 #endif /* CHTYPES_H */
 
 /** @} */
diff --git a/os/rt/include/chearly.h b/os/rt/include/chearly.h
index 6846bf6c9..e5eab0a5e 100644
--- a/os/rt/include/chearly.h
+++ b/os/rt/include/chearly.h
@@ -146,7 +146,7 @@ typedef struct ch_os_instance os_instance_t;
  *
  * @param[in] a        literal to be string-ified
  */
-#define __CH_STRINGIFY(a) #a
+#define __CH_STRINGIFY(a)   #a
 
 /**
  * @brief   Structure field offset utility.
@@ -161,6 +161,39 @@ typedef struct ch_os_instance os_instance_t;
   ((size_t)((char *)&((st *)0)->m - (char *)0))                             \
   /*lint -restore*/
 
+/**
+ * @brief   Marks an expression result as used.
+ *
+ * @param[in] x         a valid expression
+ */
+#define __CH_USED(x)    (void)(x)
+
+/**
+ * @brief   Marks a boolean expression as likely true.
+ * @note    No namespace prefix for this macro because it is commonly defined
+ *          by operating systems.
+ *
+ * @param[in] x         a valid expression
+ */
+#if defined(PORT_LIKELY) || defined(__DOXYGEN__)
+#define likely(x)       PORT_LIKELY(x)
+#else
+#define likely(x)       x
+#endif
+
+/**
+ * @brief   Marks a boolean expression as likely false.
+ * @note    No namespace prefix for this macro because it is commonly defined
+ *          by operating systems.
+ *
+ * @param[in] x         a valid expression
+ */
+#if defined(PORT_UNLIKELY) || defined(__DOXYGEN__)
+#define unlikely(x)     PORT_UNLIKELY(x)
+#else
+#define unlikely(x)     x
+#endif
+
 /*===========================================================================*/
 /* External declarations.                                                    */
 /*===========================================================================*/