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commit    697e1d02f53f985992a4f479b0b08fca5c272c6c
Author:   David Rowley <drowley@postgresql.org>
Date:     Mon Nov 23 22:29:28 2020 +0000
First released in: 14.0

    Define pg_attribute_cold and pg_attribute_hot macros
    
    For compilers supporting __has_attribute and __has_attribute (hot/cold).
    
    __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
    
    A followup commit will implement some usages of these macros.
    
    Author: David Rowley
    Reviewed-by: Andres Freund, Peter Eisentraut
    Discussion: https://postgr.es/m/CAApHDvrVpasrEzLL2er7p9iwZFZ%3DJj6WisePcFeunwfrV0js_A%40mail.gmail.com


 src/include/c.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/include/c.h b/src/include/c.h
index d5dc3632f74..ff7c2eddcec 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -191,6 +191,22 @@
 #define pg_noinline
 #endif
 
+/*
+ * Marking certain functions as "hot" or "cold" can be useful to assist the
+ * compiler in arranging the assembly code in a more efficient way.
+ */
+#if defined(__has_attribute) && __has_attribute (cold)
+#define pg_attribute_cold __attribute__((cold))
+#else
+#define pg_attribute_cold
+#endif
+
+#if defined(__has_attribute) && __has_attribute (hot)
+#define pg_attribute_hot __attribute__((hot))
+#else
+#define pg_attribute_hot
+#endif
+
 /*
  * Mark a point as unreachable in a portable fashion.  This should preferably
  * be something that the compiler understands, to aid code generation.


[parent: 3b9b01f75d6e]