eal/arm: fix debug build with gcc for 128-bit atomics

[ upstream commit 36d406c ]

Compiling with "meson build -Dbuildtype=debug --cross-file
config/arm/arm64_thunderx2_linux_gcc" shows the warnings
"function returns an aggregate [-Waggregate-return]":
../../dpdk/lib/librte_eal/arm/include/rte_atomic_64.h: In
function ‘__cas_128_relaxed’:
../../dpdk/lib/librte_eal/arm/include/rte_atomic_64.h:81:20:
error: function returns an aggregate [-Werror=aggregate-return]
 __ATOMIC128_CAS_OP(__cas_128_relaxed, "casp")
                    ^~~~~~~~~~~~~~~~~

Fix the compiling issue by defining __ATOMIC128_CAS_OP as a void
function and passing the address pointer into it.

Fixes: 7e2c3e1 ("eal/arm64: add 128-bit atomic compare exchange")

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>

lib/librte_eal/common/include/arch/arm/rte_atomic_64.h

@@ -54,15 +54,15 @@ extern "C" {
 #endif
 
 #define __ATOMIC128_CAS_OP(cas_op_name, op_string)                          \
-static __rte_noinline rte_int128_t                                          \
-cas_op_name(rte_int128_t *dst, rte_int128_t old, rte_int128_t updated)      \
+static __rte_noinline void                                                  \
+cas_op_name(rte_int128_t *dst, rte_int128_t *old, rte_int128_t updated)     \
 {                                                                           \
 	/* caspX instructions register pair must start from even-numbered
 	 * register at operand 1.
 	 * So, specify registers for local variables here.
 	 */                                                                 \
-	register uint64_t x0 __asm("x0") = (uint64_t)old.val[0];            \
-	register uint64_t x1 __asm("x1") = (uint64_t)old.val[1];            \
+	register uint64_t x0 __asm("x0") = (uint64_t)old->val[0];           \
+	register uint64_t x1 __asm("x1") = (uint64_t)old->val[1];           \
 	register uint64_t x2 __asm("x2") = (uint64_t)updated.val[0];        \
 	register uint64_t x3 __asm("x3") = (uint64_t)updated.val[1];        \
 	asm volatile(                                                       \
@@ -74,9 +74,8 @@ cas_op_name(rte_int128_t *dst, rte_int128_t old, rte_int128_t updated)      \
 		[upd1] "r" (x3),                                            \
 		[dst] "r" (dst)                                             \
 		: "memory");                                                \
-	old.val[0] = x0;                                                    \
-	old.val[1] = x1;                                                    \
-	return old;                                                         \
+	old->val[0] = x0;                                                   \
+	old->val[1] = x1;                                                   \
 }
 
 __ATOMIC128_CAS_OP(__cas_128_relaxed, "casp")
@@ -114,13 +113,14 @@ rte_atomic128_cmp_exchange(rte_int128_t *dst, rte_int128_t *exp,
 
 #if defined(__ARM_FEATURE_ATOMICS) || defined(RTE_ARM_FEATURE_ATOMICS)
 	if (success == __ATOMIC_RELAXED)
-		old = __cas_128_relaxed(dst, expected, desired);
+		__cas_128_relaxed(dst, exp, desired);
 	else if (success == __ATOMIC_ACQUIRE)
-		old = __cas_128_acquire(dst, expected, desired);
+		__cas_128_acquire(dst, exp, desired);
 	else if (success == __ATOMIC_RELEASE)
-		old = __cas_128_release(dst, expected, desired);
+		__cas_128_release(dst, exp, desired);
 	else
-		old = __cas_128_acq_rel(dst, expected, desired);
+		__cas_128_acq_rel(dst, exp, desired);
+	old = *exp;
 #else
 #define __HAS_ACQ(mo) ((mo) != __ATOMIC_RELAXED && (mo) != __ATOMIC_RELEASE)
 #define __HAS_RLS(mo) ((mo) == __ATOMIC_RELEASE || (mo) == __ATOMIC_ACQ_REL || \
@@ -184,12 +184,12 @@ rte_atomic128_cmp_exchange(rte_int128_t *dst, rte_int128_t *exp,
 #undef __STORE_128
 
 	} while (unlikely(ret));
-#endif
 
-	/* Unconditionally updating expected removes an 'if' statement.
-	 * expected should already be in register if not in the cache.
+	/* Unconditionally updating the value of exp removes an 'if' statement.
+	 * The value of exp should already be in register if not in the cache.
 	 */
 	*exp = old;
+#endif
 
 	return (old.int128 == expected.int128);
 }