linux-kernel - [PATCH v3 3/7] x86: avoid unneeded __div64

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Message-Id: <20230803082619.1369127-4-arnd@kernel.org>
Date:   Thu,  3 Aug 2023 10:26:15 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH v3 3/7] x86: avoid unneeded __div64_32 function definition

From: Arnd Bergmann <arnd@...db.de>

The __div64_32() function is provided for 32-bit architectures that
don't have a custom do_div() implementation. x86_32 has one, and
does not use the header file that declares the function prototype,
so the definition causes a W=1 warning:

lib/math/div64.c:31:32: error: no previous prototype for '__div64_32' [-Werror=missing-prototypes]

Define an empty macro to prevent the function definition from getting
built, which avoids the warning and saves a little .text space.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v3: improve code comment
---
 arch/x86/include/asm/div64.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h
index b8f1dc0761e4b..9931e4c7d73f3 100644
--- a/arch/x86/include/asm/div64.h
+++ b/arch/x86/include/asm/div64.h
@@ -71,6 +71,12 @@ static inline u64 mul_u32_u32(u32 a, u32 b)
 }
 #define mul_u32_u32 mul_u32_u32
 
+/*
+ * __div64_32() is never called on x86, so prevent the
+ * generic definition from getting built.
+ */
+#define __div64_32
+
 #else
 # include <asm-generic/div64.h>
 
-- 
2.39.2