Move the Arm implementation of UnscaledCycleClock::Now() into the header file, like the x86 implementation, so it can be more easily inlined.

PiperOrigin-RevId: 713382023
Change-Id: I2d65116865f1ebc310b9779991f5dd6f01aad77c

absl/base/internal/unscaledcycleclock.cc

diff --git a/absl/base/internal/unscaledcycleclock.cc b/absl/base/internal/unscaledcycleclock.cc
index a0bf3a6..68f9273 100644
--- a/absl/base/internal/unscaledcycleclock.cc
+++ b/absl/base/internal/unscaledcycleclock.cc
@@ -105,16 +105,6 @@
 
 #elif defined(__aarch64__)
 
-// System timer of ARMv8 runs at a different frequency than the CPU's.
-// The frequency is fixed, typically in the range 1-50MHz.  It can be
-// read at CNTFRQ special register.  We assume the OS has set up
-// the virtual timer properly.
-int64_t UnscaledCycleClock::Now() {
-  int64_t virtual_timer_value;
-  asm volatile("mrs %0, cntvct_el0" : "=r"(virtual_timer_value));
-  return virtual_timer_value;
-}
-
 double UnscaledCycleClock::Frequency() {
   uint64_t aarch64_timer_frequency;
   asm volatile("mrs %0, cntfrq_el0" : "=r"(aarch64_timer_frequency));

absl/base/internal/unscaledcycleclock.h

diff --git a/absl/base/internal/unscaledcycleclock.h b/absl/base/internal/unscaledcycleclock.h
index cc1276b..965c42d 100644
--- a/absl/base/internal/unscaledcycleclock.h
+++ b/absl/base/internal/unscaledcycleclock.h
@@ -85,6 +85,18 @@
   return static_cast<int64_t>((high << 32) | low);
 }
 
+#elif defined(__aarch64__)
+
+// System timer of ARMv8 runs at a different frequency than the CPU's.
+// The frequency is fixed, typically in the range 1-50MHz.  It can be
+// read at CNTFRQ special register.  We assume the OS has set up
+// the virtual timer properly.
+inline int64_t UnscaledCycleClock::Now() {
+  int64_t virtual_timer_value;
+  asm volatile("mrs %0, cntvct_el0" : "=r"(virtual_timer_value));
+  return virtual_timer_value;
+}
+
 #endif
 
 }  // namespace base_internal