From ff2c255af5bb2fc2e5cd3b3685f0c6283117ce73 Mon Sep 17 00:00:00 2001
From: Robert Guo <robertguo@me.com>
Date: Fri, 2 Mar 2018 06:22:03 -0500
Subject: [PATCH] Use STCK to get the CPU clock on s390x (#540)

---
 AUTHORS          | 1 +
 CONTRIBUTORS     | 1 +
 src/cycleclock.h | 5 +++++
 3 files changed, 7 insertions(+)

diff --git a/AUTHORS b/AUTHORS
index 4e4c4ed4..e574b23b 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -31,6 +31,7 @@ Kishan Kumar <kumar.kishan@outlook.com>
 Lei Xu <eddyxu@gmail.com>
 Matt Clarkson <mattyclarkson@gmail.com>
 Maxim Vafin <maxvafin@gmail.com>
+MongoDB Inc.
 Nick Hutchinson <nshutchinson@gmail.com>
 Oleksandr Sochka <sasha.sochka@gmail.com>
 Paul Redmond <paul.redmond@gmail.com>
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index c59134b9..b942722e 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -53,6 +53,7 @@ Pierre Phaneuf <pphaneuf@google.com>
 Radoslav Yovchev <radoslav.tm@gmail.com>
 Raul Marin <rmrodriguez@cartodb.com>
 Ray Glover <ray.glover@uk.ibm.com>
+Robert Guo <robert.guo@mongodb.com>
 Roman Lebedev <lebedev.ri@gmail.com>
 Shuo Chen <chenshuo@chenshuo.com>
 Tobias Ulvgård <tobias.ulvgard@dirac.se>
diff --git a/src/cycleclock.h b/src/cycleclock.h
index 4251fe4c..3b376ac5 100644
--- a/src/cycleclock.h
+++ b/src/cycleclock.h
@@ -159,6 +159,11 @@ inline BENCHMARK_ALWAYS_INLINE int64_t Now() {
   struct timeval tv;
   gettimeofday(&tv, nullptr);
   return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
+#elif defined(__s390__) // Covers both s390 and s390x.
+  // Return the CPU clock.
+  uint64_t tsc;
+  asm("stck %0" : "=Q" (tsc) : : "cc");
+  return tsc;
 #else
 // The soft failover to a generic implementation is automatic only for ARM.
 // For other platforms the developer is expected to make an attempt to create