ART: Clean up arm64 kNumberOfXRegisters usage.

Avoid undefined behavior for arm64 stemming from 1u << 32 in
loops with upper bound kNumberOfXRegisters.

Create iterators for enumerating bits in an integer either
from high to low or from low to high and use them for
<arch>Context::FillCalleeSaves() on all architectures.

Refactor runtime/utils.{h,cc} by moving all bit-fiddling
functions to runtime/base/bit_utils.{h,cc} (together with
the new bit iterators) and all time-related functions to
runtime/base/time_utils.{h,cc}. Improve test coverage and
fix some corner cases for the bit-fiddling functions.

Bug: 13925192
Change-Id: I704884dab15b41ecf7a1c47d397ab1c3fc7ee0f7
diff --git a/runtime/base/time_utils.cc b/runtime/base/time_utils.cc
new file mode 100644
index 0000000..29b849e
--- /dev/null
+++ b/runtime/base/time_utils.cc
@@ -0,0 +1,205 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <inttypes.h>
+#include <sstream>
+
+#include "time_utils.h"
+
+#include "base/logging.h"
+#include "base/stringprintf.h"
+
+namespace art {
+
+std::string PrettyDuration(uint64_t nano_duration, size_t max_fraction_digits) {
+  if (nano_duration == 0) {
+    return "0";
+  } else {
+    return FormatDuration(nano_duration, GetAppropriateTimeUnit(nano_duration),
+                          max_fraction_digits);
+  }
+}
+
+TimeUnit GetAppropriateTimeUnit(uint64_t nano_duration) {
+  const uint64_t one_sec = 1000 * 1000 * 1000;
+  const uint64_t one_ms  = 1000 * 1000;
+  const uint64_t one_us  = 1000;
+  if (nano_duration >= one_sec) {
+    return kTimeUnitSecond;
+  } else if (nano_duration >= one_ms) {
+    return kTimeUnitMillisecond;
+  } else if (nano_duration >= one_us) {
+    return kTimeUnitMicrosecond;
+  } else {
+    return kTimeUnitNanosecond;
+  }
+}
+
+uint64_t GetNsToTimeUnitDivisor(TimeUnit time_unit) {
+  const uint64_t one_sec = 1000 * 1000 * 1000;
+  const uint64_t one_ms  = 1000 * 1000;
+  const uint64_t one_us  = 1000;
+
+  switch (time_unit) {
+    case kTimeUnitSecond:
+      return one_sec;
+    case kTimeUnitMillisecond:
+      return one_ms;
+    case kTimeUnitMicrosecond:
+      return one_us;
+    case kTimeUnitNanosecond:
+      return 1;
+  }
+  return 0;
+}
+
+std::string FormatDuration(uint64_t nano_duration, TimeUnit time_unit,
+                           size_t max_fraction_digits) {
+  const char* unit = nullptr;
+  uint64_t divisor = GetNsToTimeUnitDivisor(time_unit);
+  switch (time_unit) {
+    case kTimeUnitSecond:
+      unit = "s";
+      break;
+    case kTimeUnitMillisecond:
+      unit = "ms";
+      break;
+    case kTimeUnitMicrosecond:
+      unit = "us";
+      break;
+    case kTimeUnitNanosecond:
+      unit = "ns";
+      break;
+  }
+  const uint64_t whole_part = nano_duration / divisor;
+  uint64_t fractional_part = nano_duration % divisor;
+  if (fractional_part == 0) {
+    return StringPrintf("%" PRIu64 "%s", whole_part, unit);
+  } else {
+    static constexpr size_t kMaxDigits = 30;
+    size_t avail_digits = kMaxDigits;
+    char fraction_buffer[kMaxDigits];
+    char* ptr = fraction_buffer;
+    uint64_t multiplier = 10;
+    // This infinite loops if fractional part is 0.
+    while (avail_digits > 1 && fractional_part * multiplier < divisor) {
+      multiplier *= 10;
+      *ptr++ = '0';
+      avail_digits--;
+    }
+    snprintf(ptr, avail_digits, "%" PRIu64, fractional_part);
+    fraction_buffer[std::min(kMaxDigits - 1, max_fraction_digits)] = '\0';
+    return StringPrintf("%" PRIu64 ".%s%s", whole_part, fraction_buffer, unit);
+  }
+}
+
+std::string GetIsoDate() {
+  time_t now = time(nullptr);
+  tm tmbuf;
+  tm* ptm = localtime_r(&now, &tmbuf);
+  return StringPrintf("%04d-%02d-%02d %02d:%02d:%02d",
+      ptm->tm_year + 1900, ptm->tm_mon+1, ptm->tm_mday,
+      ptm->tm_hour, ptm->tm_min, ptm->tm_sec);
+}
+
+uint64_t MilliTime() {
+#if defined(__linux__)
+  timespec now;
+  clock_gettime(CLOCK_MONOTONIC, &now);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000) + now.tv_nsec / UINT64_C(1000000);
+#else  // __APPLE__
+  timeval now;
+  gettimeofday(&now, nullptr);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000) + now.tv_usec / UINT64_C(1000);
+#endif
+}
+
+uint64_t MicroTime() {
+#if defined(__linux__)
+  timespec now;
+  clock_gettime(CLOCK_MONOTONIC, &now);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000000) + now.tv_nsec / UINT64_C(1000);
+#else  // __APPLE__
+  timeval now;
+  gettimeofday(&now, nullptr);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000000) + now.tv_usec;
+#endif
+}
+
+uint64_t NanoTime() {
+#if defined(__linux__)
+  timespec now;
+  clock_gettime(CLOCK_MONOTONIC, &now);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000000000) + now.tv_nsec;
+#else  // __APPLE__
+  timeval now;
+  gettimeofday(&now, nullptr);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000000000) + now.tv_usec * UINT64_C(1000);
+#endif
+}
+
+uint64_t ThreadCpuNanoTime() {
+#if defined(__linux__)
+  timespec now;
+  clock_gettime(CLOCK_THREAD_CPUTIME_ID, &now);
+  return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000000000) + now.tv_nsec;
+#else  // __APPLE__
+  UNIMPLEMENTED(WARNING);
+  return -1;
+#endif
+}
+
+void NanoSleep(uint64_t ns) {
+  timespec tm;
+  tm.tv_sec = ns / MsToNs(1000);
+  tm.tv_nsec = ns - static_cast<uint64_t>(tm.tv_sec) * MsToNs(1000);
+  nanosleep(&tm, nullptr);
+}
+
+void InitTimeSpec(bool absolute, int clock, int64_t ms, int32_t ns, timespec* ts) {
+  int64_t endSec;
+
+  if (absolute) {
+#if !defined(__APPLE__)
+    clock_gettime(clock, ts);
+#else
+    UNUSED(clock);
+    timeval tv;
+    gettimeofday(&tv, nullptr);
+    ts->tv_sec = tv.tv_sec;
+    ts->tv_nsec = tv.tv_usec * 1000;
+#endif
+  } else {
+    ts->tv_sec = 0;
+    ts->tv_nsec = 0;
+  }
+  endSec = ts->tv_sec + ms / 1000;
+  if (UNLIKELY(endSec >= 0x7fffffff)) {
+    std::ostringstream ss;
+    LOG(INFO) << "Note: end time exceeds epoch: " << ss.str();
+    endSec = 0x7ffffffe;
+  }
+  ts->tv_sec = endSec;
+  ts->tv_nsec = (ts->tv_nsec + (ms % 1000) * 1000000) + ns;
+
+  // Catch rollover.
+  if (ts->tv_nsec >= 1000000000L) {
+    ts->tv_sec++;
+    ts->tv_nsec -= 1000000000L;
+  }
+}
+
+}  // namespace art