Add support for z/OS XL compiler inline asm syntax (#1063)

On s390 architecture, z/OS XL compiler uses HLASM inline assembly, which has different syntax and needs to be distinguished to avoid compilation error.

CONTRIBUTORS

@@ -41,6 +41,7 @@ Eric Backus <eric_backus@alum.mit.edu>
 Eric Fiselier <eric@efcs.ca>
 Eugene Zhuk <eugene.zhuk@gmail.com>
 Evgeny Safronov <division494@gmail.com>
+Fanbo Meng <fanbo.meng@ibm.com>
 Federico Ficarelli <federico.ficarelli@gmail.com>
 Felix Homann <linuxaudio@showlabor.de>
 Geoffrey Martin-Noble <gcmn@google.com> <gmngeoffrey@gmail.com>

src/cycleclock.h

@@ -170,7 +170,12 @@ inline BENCHMARK_ALWAYS_INLINE int64_t Now() {
 #elif defined(__s390__)  // Covers both s390 and s390x.
   // Return the CPU clock.
   uint64_t tsc;
+#if defined(BENCHMARK_OS_ZOS) && defined(COMPILER_IBMXL)
+  // z/OS XL compiler HLASM syntax.
+  asm(" stck %0" : "=m"(tsc) : : "cc");
+#else
   asm("stck %0" : "=Q"(tsc) : : "cc");
+#endif
   return tsc;
 #elif defined(__riscv) // RISC-V
   // Use RDCYCLE (and RDCYCLEH on riscv32)

src/internal_macros.h

@@ -13,7 +13,11 @@
 #endif
 
 #if defined(__clang__)
-  #if !defined(COMPILER_CLANG)
+  #if defined(__ibmxl__)
+    #if !defined(COMPILER_IBMXL)
+      #define COMPILER_IBMXL
+    #endif
+  #elif !defined(COMPILER_CLANG)
     #define COMPILER_CLANG
   #endif
 #elif defined(_MSC_VER)
@@ -74,6 +78,8 @@
 #define BENCHMARK_OS_SOLARIS 1
 #elif defined(__QNX__)
 #define BENCHMARK_OS_QNX 1
+#elif defined(__MVS__)
+#define BENCHMARK_OS_ZOS 1
 #endif
 
 #if defined(__ANDROID__) && defined(__GLIBCXX__)