linux-kernel - [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE

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Message-Id: <20200507224530.2993316-1-Jason@zx2c4.com>
Date:   Thu,  7 May 2020 16:45:30 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE_O3 for gcc >= 10

GCC 10 appears to have changed -O2 in order to make compilation time
faster when using -flto, seemingly at the expense of performance, in
particular with regards to how the inliner works. Since -O3 these days
shouldn't have the same set of bugs as 10 years ago, this commit
defaults new kernel compiles to -O3 when using gcc >= 10.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 init/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 9e22ee8fbd75..fab3f810a68d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1245,7 +1245,8 @@ config BOOT_CONFIG
 
 choice
 	prompt "Compiler optimization level"
-	default CC_OPTIMIZE_FOR_PERFORMANCE
+	default CC_OPTIMIZE_FOR_PERFORMANCE_O3 if GCC_VERSION >= 100000
+	default CC_OPTIMIZE_FOR_PERFORMANCE if (GCC_VERSION < 100000 || CC_IS_CLANG)
 
 config CC_OPTIMIZE_FOR_PERFORMANCE
 	bool "Optimize for performance (-O2)"
-- 
2.26.2