Initial support for AIX (#1021)

* Init support of AIX

* make sysinfo change AIX specific

* Relocate TBF

* Add comments for .csect psudo op.

absl/base/attributes.h

@@ -318,8 +318,16 @@
 // `__start_ ## name` and `__stop_ ## name` symbols to bracket the section.
 // This functionality is supported by GNU linker.
 #ifndef ABSL_ATTRIBUTE_SECTION_VARIABLE
+#ifdef _AIX
+// __attribute__((section(#name))) on AIX is achived by using the `.csect` psudo
+// op which includes an additional integer as part of its syntax indcating
+// alignment. If data fall under different alignments then you might get a
+// compilation error indicating a `Section type conflict`.
+#define ABSL_ATTRIBUTE_SECTION_VARIABLE(name)
+#else
 #define ABSL_ATTRIBUTE_SECTION_VARIABLE(name) __attribute__((section(#name)))
 #endif
+#endif
 
 // ABSL_DECLARE_ATTRIBUTE_SECTION_VARS
 //

absl/base/config.h

@@ -408,10 +408,10 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 // POSIX.1-2001.
 #ifdef ABSL_HAVE_MMAP
 #error ABSL_HAVE_MMAP cannot be directly set
-#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) ||   \
-    defined(__ros__) || defined(__native_client__) || defined(__asmjs__) || \
-    defined(__wasm__) || defined(__Fuchsia__) || defined(__sun) || \
-    defined(__ASYLO__) || defined(__myriad2__)
+#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
+    defined(_AIX) || defined(__ros__) || defined(__native_client__) ||    \
+    defined(__asmjs__) || defined(__wasm__) || defined(__Fuchsia__) ||    \
+    defined(__sun) || defined(__ASYLO__) || defined(__myriad2__)
 #define ABSL_HAVE_MMAP 1
 #endif
 
@@ -422,7 +422,7 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
 #error ABSL_HAVE_PTHREAD_GETSCHEDPARAM cannot be directly set
 #elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
-    defined(__ros__)
+    defined(_AIX) || defined(__ros__)
 #define ABSL_HAVE_PTHREAD_GETSCHEDPARAM 1
 #endif
 

absl/base/internal/sysinfo.cc

@@ -131,6 +131,8 @@ static int GetNumCPUs() {
 #elif defined(_WIN32)
   const unsigned hardware_concurrency = Win32NumCPUs();
   return hardware_concurrency ? hardware_concurrency : 1;
+#elif defined(_AIX)
+  return sysconf(_SC_NPROCESSORS_ONLN);
 #else
   // Other possibilities:
   //  - Read /sys/devices/system/cpu/online and use cpumask_parse()

absl/base/internal/unscaledcycleclock.cc

@@ -87,6 +87,10 @@ int64_t UnscaledCycleClock::Now() {
 double UnscaledCycleClock::Frequency() {
 #ifdef __GLIBC__
   return __ppc_get_timebase_freq();
+#elif defined(_AIX)
+  // This is the same constant value as returned by
+  // __ppc_get_timebase_freq().
+  return static_cast<double>(512000000);
 #elif defined(__FreeBSD__)
   static once_flag init_timebase_frequency_once;
   static double timebase_frequency = 0.0;

absl/time/clock_test.cc

@@ -18,6 +18,8 @@
 #if defined(ABSL_HAVE_ALARM)
 #include <signal.h>
 #include <unistd.h>
+#elif defined(_AIX)
+typedef void (*sig_t)(int);
 #elif defined(__linux__) || defined(__APPLE__)
 #error all known Linux and Apple targets have alarm
 #endif