Get rid of tail padding within `absl::Duration`. This reduces memory usage needs when storing duration in containers (e.g. `vector<absl::Duration>` uses 25% less memory), and allows classes with `absl::Duration` fields to fit other stuff in memory previously used by tail padding (e.g. `std::optional<absl::Duration>` is now 16 bytes instead of 24).

PiperOrigin-RevId: 506543503
Change-Id: Ifeb2397c953a5d3da317a70ab49a3ebb85042344

1 files changed, 22 insertions, 17 deletions

diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index 911e80f8..b915d749 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -407,16 +407,18 @@ int64_t IDivDuration(bool satq, const Duration num, const Duration den,
 Duration& Duration::operator+=(Duration rhs) {
   if (time_internal::IsInfiniteDuration(*this)) return *this;
   if (time_internal::IsInfiniteDuration(rhs)) return *this = rhs;
-  const int64_t orig_rep_hi = rep_hi_;
-  rep_hi_ =
-      DecodeTwosComp(EncodeTwosComp(rep_hi_) + EncodeTwosComp(rhs.rep_hi_));
+  const int64_t orig_rep_hi = rep_hi_.Get();
+  rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) +
+                           EncodeTwosComp(rhs.rep_hi_.Get()));
   if (rep_lo_ >= kTicksPerSecond - rhs.rep_lo_) {
-    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_) + 1);
+    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) + 1);
     rep_lo_ -= kTicksPerSecond;
   }
   rep_lo_ += rhs.rep_lo_;
-  if (rhs.rep_hi_ < 0 ? rep_hi_ > orig_rep_hi : rep_hi_ < orig_rep_hi) {
-    return *this = rhs.rep_hi_ < 0 ? -InfiniteDuration() : InfiniteDuration();
+  if (rhs.rep_hi_.Get() < 0 ? rep_hi_.Get() > orig_rep_hi
+                            : rep_hi_.Get() < orig_rep_hi) {
+    return *this =
+               rhs.rep_hi_.Get() < 0 ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this;
 }
@@ -424,18 +426,21 @@ Duration& Duration::operator+=(Duration rhs) {
 Duration& Duration::operator-=(Duration rhs) {
   if (time_internal::IsInfiniteDuration(*this)) return *this;
   if (time_internal::IsInfiniteDuration(rhs)) {
-    return *this = rhs.rep_hi_ >= 0 ? -InfiniteDuration() : InfiniteDuration();
+    return *this = rhs.rep_hi_.Get() >= 0 ? -InfiniteDuration()
+                                          : InfiniteDuration();
   }
-  const int64_t orig_rep_hi = rep_hi_;
-  rep_hi_ =
-      DecodeTwosComp(EncodeTwosComp(rep_hi_) - EncodeTwosComp(rhs.rep_hi_));
+  const int64_t orig_rep_hi = rep_hi_.Get();
+  rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) -
+                           EncodeTwosComp(rhs.rep_hi_.Get()));
   if (rep_lo_ < rhs.rep_lo_) {
-    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_) - 1);
+    rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_.Get()) - 1);
     rep_lo_ += kTicksPerSecond;
   }
   rep_lo_ -= rhs.rep_lo_;
-  if (rhs.rep_hi_ < 0 ? rep_hi_ < orig_rep_hi : rep_hi_ > orig_rep_hi) {
-    return *this = rhs.rep_hi_ >= 0 ? -InfiniteDuration() : InfiniteDuration();
+  if (rhs.rep_hi_.Get() < 0 ? rep_hi_.Get() < orig_rep_hi
+                            : rep_hi_.Get() > orig_rep_hi) {
+    return *this = rhs.rep_hi_.Get() >= 0 ? -InfiniteDuration()
+                                          : InfiniteDuration();
   }
   return *this;
 }
@@ -446,7 +451,7 @@ Duration& Duration::operator-=(Duration rhs) {
 
 Duration& Duration::operator*=(int64_t r) {
   if (time_internal::IsInfiniteDuration(*this)) {
-    const bool is_neg = (r < 0) != (rep_hi_ < 0);
+    const bool is_neg = (r < 0) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleFixed<SafeMultiply>(*this, r);
@@ -454,7 +459,7 @@ Duration& Duration::operator*=(int64_t r) {
 
 Duration& Duration::operator*=(double r) {
   if (time_internal::IsInfiniteDuration(*this) || !IsFinite(r)) {
-    const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0);
+    const bool is_neg = std::signbit(r) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleDouble<std::multiplies>(*this, r);
@@ -462,7 +467,7 @@ Duration& Duration::operator*=(double r) {
 
 Duration& Duration::operator/=(int64_t r) {
   if (time_internal::IsInfiniteDuration(*this) || r == 0) {
-    const bool is_neg = (r < 0) != (rep_hi_ < 0);
+    const bool is_neg = (r < 0) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleFixed<std::divides>(*this, r);
@@ -470,7 +475,7 @@ Duration& Duration::operator/=(int64_t r) {
 
 Duration& Duration::operator/=(double r) {
   if (time_internal::IsInfiniteDuration(*this) || !IsValidDivisor(r)) {
-    const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0);
+    const bool is_neg = std::signbit(r) != (rep_hi_.Get() < 0);
     return *this = is_neg ? -InfiniteDuration() : InfiniteDuration();
   }
   return *this = ScaleDouble<std::divides>(*this, r);