configure: Check for support for labels in the inline assembly

Use this for enabling the ppc timer.h implementation only on
assemblers that support labels in the inline assembly.
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -1294,6 +1294,7 @@ HAVE_LIST="
     ibm_asm
     inet_aton
     io_h
+    inline_asm_labels
     isatty
     jack_port_get_latency_range
     ldbrx
@@ -3405,6 +3406,8 @@ unsigned int endian = 'B' << 24 | 'I' << 16 | 'G' << 8 | 'E';
 EOF
 od -t x1 $TMPO | grep -q '42 *49 *47 *45' && enable bigendian
 
+check_inline_asm inline_asm_labels '"1:\n"'
+
 if enabled alpha; then
 
     check_cflags -mieee

libavutil/ppc/timer.h

@@ -23,6 +23,10 @@
 
 #include <stdint.h>
 
+#include "config.h"
+
+#if HAVE_INLINE_ASM_LABELS
+
 #define AV_READ_TIME read_time
 
 static inline uint64_t read_time(void)
@@ -44,4 +48,6 @@ static inline uint64_t read_time(void)
      return (((uint64_t)tbu)<<32) | (uint64_t)tbl;
 }
 
+#endif /* HAVE_INLINE_ASM_LABELS */
+
 #endif /* AVUTIL_PPC_TIMER_H */