eal/x86: fix build with clang for old AVX

When configuring RTE_MACHINE to "default", rte_memcpy implementation
is the default one (old AVX).
In this code, clang raises a warning thanks to -Wsometimes-uninitialized:

rte_memcpy.h:838:6: error:
variable 'srcofs' is used uninitialized whenever 'if' condition is false
        if (dstofss > 0) {
            ^~~~~~~~~~~
rte_memcpy.h:849:6: note: uninitialized use occurs here
        if (srcofs == 0) {
            ^~~~~~

It is fixed by moving srcofs initialization out of the condition.
Also dstofss calculation is corrected.

Fixes: 1ae817f9f887 ("eal/x86: tune memcpy for platforms without AVX512")

Reported-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>

diff --git a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
index 8e2c53c..f463ab3 100644 (file)
--- a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
+++ b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
@@ -512,8 +512,9 @@ COPY_BLOCK_64_BACK31:
        /**
         * Make store aligned when copy size exceeds 512 bytes
         */
-       dstofss = 32 - ((uintptr_t)dst & 0x1F);
+       dstofss = (uintptr_t)dst & 0x1F;
        if (dstofss > 0) {
+               dstofss = 32 - dstofss;
                n -= dstofss;
                rte_mov32((uint8_t *)dst, (const uint8_t *)src);
                src = (const uint8_t *)src + dstofss;
@@ -834,14 +835,15 @@ COPY_BLOCK_64_BACK15:
         * unaligned copy functions require up to 15 bytes
         * backwards access.
         */
-       dstofss = 16 - ((uintptr_t)dst & 0x0F) + 16;
+       dstofss = (uintptr_t)dst & 0x0F;
        if (dstofss > 0) {
+               dstofss = 16 - dstofss + 16;
                n -= dstofss;
                rte_mov32((uint8_t *)dst, (const uint8_t *)src);
                src = (const uint8_t *)src + dstofss;
                dst = (uint8_t *)dst + dstofss;
-               srcofs = ((uintptr_t)src & 0x0F);
        }
+       srcofs = ((uintptr_t)src & 0x0F);
 
        /**
         * For aligned copy