eal/arm: fix clang build of native target

When doing Clang build with '-mcpu=native' on N1 platform, build failed
with:
../lib/librte_eal/arm/include/rte_atomic_64.h:76:39:
	error: instruction requires: lse
__ATOMIC128_CAS_OP(__cas_128_release, "caspl")

This is because native detection for Neoverse N1 was added in Clang-11.
Prior version of Clang's assembler doesn't know LSE support on hardware.
Fixed this for Clang earlier than version 11 by specifying architecture
for assembler.
Referred to [1] for this fix.

Fixes: 7e2c3e17fe2c ("eal/arm64: add 128-bit atomic compare exchange")
Cc: stable@dpdk.org
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e0d5896bd356cd577f9710a02d7a474cdf58426b

Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Jerin Jacob <jerinj@marvell.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

diff --git a/lib/librte_eal/arm/include/rte_atomic_64.h b/lib/librte_eal/arm/include/rte_atomic_64.h
index 2cef886..7fcd174 100644 (file)
--- a/lib/librte_eal/arm/include/rte_atomic_64.h
+++ b/lib/librte_eal/arm/include/rte_atomic_64.h
@@ -46,6 +46,8 @@ rte_atomic_thread_fence(int memorder)
 /*------------------------ 128 bit atomic operations -------------------------*/
 
 #if defined(__ARM_FEATURE_ATOMICS) || defined(RTE_ARM_FEATURE_ATOMICS)
+#define __LSE_PREAMBLE ".arch armv8-a+lse\n"
+
 #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)      \
@@ -59,6 +61,7 @@ cas_op_name(rte_int128_t *dst, rte_int128_t old, rte_int128_t updated)      \
        register uint64_t x2 __asm("x2") = (uint64_t)updated.val[0];        \
        register uint64_t x3 __asm("x3") = (uint64_t)updated.val[1];        \
        asm volatile(                                                       \
+               __LSE_PREAMBLE                                              \
                op_string " %[old0], %[old1], %[upd0], %[upd1], [%[dst]]"   \
                : [old0] "+r" (x0),                                         \
                [old1] "+r" (x1)                                            \
@@ -76,6 +79,7 @@ __ATOMIC128_CAS_OP(__cas_128_acquire, "caspa")
 __ATOMIC128_CAS_OP(__cas_128_release, "caspl")
 __ATOMIC128_CAS_OP(__cas_128_acq_rel, "caspal")
 
+#undef __LSE_PREAMBLE
 #undef __ATOMIC128_CAS_OP
 
 #endif