x86/csum: Fix clang -Wuninitialized in csum_partial()

Clang warns:

  arch/x86/lib/csum-partial_64.c:74:20: error: variable 'result' is uninitialized when used here [-Werror,-Wuninitialized]
                  return csum_tail(result, temp64, odd);
                                   ^~~~~~
  arch/x86/lib/csum-partial_64.c:48:22: note: initialize the variable 'result' to silence this warning
          unsigned odd, result;
                              ^
                               = 0
  1 error generated.

The only initialization and uses of result in csum_partial() were moved
into csum_tail() but result is still being passed by value to
csum_tail() (clang's -Wuninitialized does not do interprocedural
analysis to realize that result is always assigned in csum_tail()
however). Sink the declaration of result into csum_tail() to clear up
the warning.

Closes: https://lore.kernel.org/202305262039.3HUYjWJk-lkp@intel.com/
Fixes: 688eb8191b47 ("x86/csum: Improve performance of `csum_partial`")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20230526-csum_partial-wuninitialized-v1-1-ebc0108dcec1%40kernel.org

diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index fe5861951b159836074486acd599d7f5808be38c..cea25ca8b8cf69885a2de752c3bc1fb067cded26 100644 (file)
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -21,8 +21,10 @@ static inline unsigned short from32to16(unsigned a)
        return b;
 }
 
-static inline __wsum csum_tail(unsigned int result, u64 temp64, int odd)
+static inline __wsum csum_tail(u64 temp64, int odd)
 {
+       unsigned int result;
+
        result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff);
        if (unlikely(odd)) {
                result = from32to16(result);
@@ -45,7 +47,7 @@ static inline __wsum csum_tail(unsigned int result, u64 temp64, int odd)
 __wsum csum_partial(const void *buff, int len, __wsum sum)
 {
        u64 temp64 = (__force u64)sum;
-       unsigned odd, result;
+       unsigned odd;
 
        odd = 1 & (unsigned long) buff;
        if (unlikely(odd)) {
@@ -71,7 +73,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
                    "adcq $0,%[res]"
                    : [res] "+r"(temp64)
                    : [src] "r"(buff), "m"(*(const char(*)[40])buff));
-               return csum_tail(result, temp64, odd);
+               return csum_tail(temp64, odd);
        }
        if (unlikely(len >= 64)) {
                /*
@@ -141,7 +143,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
                    : [res] "+r"(temp64)
                    : [trail] "r"(trail));
        }
-       return csum_tail(result, temp64, odd);
+       return csum_tail(temp64, odd);
 }
 EXPORT_SYMBOL(csum_partial);