Extract arm64 asm check

PiperOrigin-RevId: 823185820

Author: protobuf-github-bot

upb/port/def.inc

@@ -392,6 +392,12 @@ Error, UINTPTR_MAX is undefined
 #define UPB_PRESERVE_NONE
 #endif
 
+#if defined(__aarch64__) && (defined(__GNUC__) || defined(__clang__))
+#define UPB_ARM64_ASM 1
+#else
+#define UPB_ARM64_ASM 0
+#endif
+
 /* This check is not fully robust: it does not require that we have "musttail"
  * support available. We need tail calls to avoid consuming arbitrary amounts
  * of stack space.

upb/port/undef.inc

@@ -82,3 +82,4 @@
 #undef UPB_XSAN
 #undef UPB_XSAN_STRUCT_SIZE
 #undef UPB_ENABLE_REF_CYCLE_CHECKS
+#undef UPB_ARM64_ASM

upb/wire/encode.c

@@ -141,15 +141,9 @@ static char* encode_fixed32(char* ptr, upb_encstate* e, uint32_t val) {
 
 #define UPB_PB_VARINT_MAX_LEN 10
 
-// Need gnu extended inline asm; msan can't instrument stores in inline assembly
-#if defined(__aarch64__) && (defined(__GNUC__) || defined(__clang__)) && \
-    !UPB_HAS_FEATURE(memory_sanitizer)
-#define UPB_ARM64_ASM
-#endif
-
-#ifdef UPB_ARM64_ASM
-UPB_NOINLINE static char* encode_longvarint_arm64(char* ptr, upb_encstate* e,
-                                                  uint64_t val) {
+#if UPB_ARM64_ASM
+UPB_NOINLINE static char* encode_longvarint(char* ptr, upb_encstate* e,
+                                            uint64_t val) {
   ptr = encode_reserve(ptr, e, UPB_PB_VARINT_MAX_LEN);
   uint64_t clz;
   __asm__("clz %[cnt], %[val]\n" : [cnt] "=r"(clz) : [val] "r"(val));
@@ -223,11 +217,7 @@ char* encode_varint(char* ptr, upb_encstate* e, uint64_t val) {
     *ptr = val;
     return ptr;
   } else {
-#ifdef UPB_ARM64_ASM
-    return encode_longvarint_arm64(ptr, e, val);
-#else
     return encode_longvarint(ptr, e, val);
-#endif
   }
 }