From: Willy Tarreau <w@1wt.eu>
Date: Tue, 17 Dec 2024 08:19:20 +0000 (+0100)
Subject: MINOR: compiler: also enable __builtin_assume() for ASSUME()
X-Git-Tag: v3.2-dev2~58
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2ce63b7b17c45e31ef8c3dec33b9b54aea656154;p=thirdparty%2Fhaproxy.git

MINOR: compiler: also enable __builtin_assume() for ASSUME()

Clang apparently has __builtin_assume() which does exactly the same
as our macro, since at least v3.8. Let's enable it, in case it may
even better detect assumptions vs unreachable code.
---

diff --git a/include/haproxy/compiler.h b/include/haproxy/compiler.h
index dbafdac59e..c3a610aed9 100644
--- a/include/haproxy/compiler.h
+++ b/include/haproxy/compiler.h
@@ -219,9 +219,11 @@
  * know that some conditions are not supposed to happen. This can only be used
  * with compilers that support it, and we do not want to emit any static code
  * for other ones, so we use a construct that the compiler should easily be
- * able to optimize away.
+ * able to optimize away. Clang also has __builtin_assume() since at least 3.x.
  */
-#if __has_builtin(__builtin_unreachable)
+#if __has_builtin(__builtin_assume)
+# define ASSUME(expr) __builtin_assume(expr)
+#elif __has_builtin(__builtin_unreachable)
 # define ASSUME(expr) do { if (!(expr)) __builtin_unreachable(); } while (0)
 #else
 # define ASSUME(expr) do { if (!(expr)) break; } while (0)