[PATCH v3 1/3] MdePkg: add RETURNS_TWICE attribute

[M1cha <sigmaepsilon92@gmail.com>]

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Michael Zimmermann <sigmaepsilon92@gmail.com>
---
V3: add code comments

 MdePkg/Include/Base.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/MdePkg/Include/Base.h b/MdePkg/Include/Base.h
index 22ab5d3715fb..8c7345609ed5 100644
--- a/MdePkg/Include/Base.h
+++ b/MdePkg/Include/Base.h
@@ -218,6 +218,26 @@ VERIFY_SIZE_OF (__VERIFY_UINT32_ENUM_SIZE, 4);
   #endif
 #endif
 
+///
+/// Tell the code optimizer that the function will return twice.
+/// This prevents wrong optimizations which can cause bugs.
+///
+#ifndef RETURNS_TWICE
+  #if defined (__GNUC__) || defined (__clang__)
+    ///
+    /// Tell the code optimizer that the function will return twice.
+    /// This prevents wrong optimizations which can cause bugs.
+    ///
+    #define RETURNS_TWICE  __attribute__((returns_twice))
+  #else
+    ///
+    /// Tell the code optimizer that the function will return twice.
+    /// This prevents wrong optimizations which can cause bugs.
+    ///
+    #define RETURNS_TWICE
+  #endif
+#endif
+
 //
 // For symbol name in assembly code, an extra "_" is sometimes necessary
 //
-- 
2.15.1