From 3626bdf4badfa991a6c11ad2113bf184562b3494 Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fl.fischer@fau.de>
Date: Mon, 29 Mar 2021 19:39:33 +0200
Subject: [PATCH] [Debug.hpp] wrap actual logging in log-level constexpr
According to godbolt.org
do { if constexpr(false) { break; } int foo = 42; foo++; } while(false);
does result in code generation for gcc 10.2 and clang 11.0.1 as opposed to
do { if constexpr(false) { int foo = 42; foo++; }} while(false);
which does not result in code generation for both gcc and clang.
And this simple change did indeed significantly increases our echo
benchmark performance. We were probably creating a lot of std::stringstream
objects without ever using them.
---
emper/Debug.hpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/emper/Debug.hpp b/emper/Debug.hpp
index 06cdd502..3b207771 100644
--- a/emper/Debug.hpp
+++ b/emper/Debug.hpp
@@ -21,7 +21,7 @@
#define EMPER_BUILD_STR(x) [&]() -> std::string {std::stringstream sst; sst << x; return sst.str(); }
// NOLINTNEXTLINE(bugprone-macro-parentheses)
-#define LOG(level, x, log_func) do {if constexpr (level > EMPER_LOG_LEVEL) { break; } log_func(EMPER_BUILD_STR(x)()); } while (false)
+#define LOG(level, x, log_func) do { if constexpr (level <= EMPER_LOG_LEVEL) { log_func(EMPER_BUILD_STR(x)()); } } while (false)
// NOLINTNEXTLINE(bugprone-macro-parentheses)
#define DBG(x) LOG(Debug, x, emper_log_no_prefix);
--
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