Export of internal Abseil changes

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1620e8ffaa93ef24510ca60c7fff2a07248ac9f6 by Abseil Team <absl-team@google.com>:

Update comment.

PiperOrigin-RevId: 382858259

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20db116f28469149d10e0f7f8b976cb903dd4879 by Gennadiy Rozental <rogeeff@google.com>:

Add benchmark running on multiple flags.

Update size_tester to include cost of absl::GetFlag call.
Add size_tester invocation for bool flag.

New benchmark better represent GetFlag usage.

PiperOrigin-RevId: 382820341

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2e097ad3811c4e329f75b98877a5e74c1d3d84fd by Abseil Team <absl-team@google.com>:

Avoid 64x64->128 multiplication in absl::Hash's mix on AArch64

On AArch64, calculating a 128-bit product is inefficient, because it requires a sequence of two instructions to calculate the upper and lower halves of the result. So calculate a 64-bit product instead.

Making MultType 64-bits means the upper 32 bits of the result do not participate in shift/xor, but the add/multiply gives us sufficient mixing.

PiperOrigin-RevId: 382625931

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f3ae3f32cb53168c8dc91b766f2932dc87cec503 by Abseil Team <absl-team@google.com>:

Remove homegrown Round implementation

absl/time/duration.cc defined a Round implementation to accommodate old
versions of MSVC that lacked std::round(long double). Abseil no longer
supports those MSVCs, so we don’t need the homegrown implementation
anymore. Remove it, and replace calls to it with std::rint.

PiperOrigin-RevId: 382605191

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a13631c91bf5478289e1a512ce215c85501a26f7 by Martijn Vels <mvels@google.com>:

Move the Consume() conversion functions out of cord_rep_ring into cord_rep_consume.

This makes these functions generic, so we can repurpose these for the new Btree conversion functions.

PiperOrigin-RevId: 382594902

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7394c737500c2d8371fcf913b21ad1b321ba499d by Benjamin Barenblat <bbaren@google.com>:

Remove homegrown Round implementation

absl/time/duration.cc defined a Round implementation to accommodate old
versions of MSVC that lacked std::round(long double). Abseil no longer
supports those MSVCs, so we don’t need the homegrown implementation
anymore. Remove it, and replace calls to it with std::rint.

PiperOrigin-RevId: 382569900

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d72a761f43dc5c9b9510c3a1363177ed26646b5d by Abseil Team <absl-team@google.com>:

Prefer `getentropy` for Emscripten.

It needs a different header, so I've separated it out from the GLIBC
check above.

PiperOrigin-RevId: 382332475

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74e261dbb467741b2ddd8b490e04c531fdd2f559 by Martijn Vels <mvels@google.com>:

Add BTREE tag for CordRepNode implementing a Btree cord.

This change only forward declared the CordRepBtree class (not implemented yet) and defines the enum value BTREE. While RING and BTREE should never co-exist, we define a new value for BTREE so as not to make transitioning between RING and BTREE harder than it needs to be. This changes shifts the FLAT value / computation from FLAT = 4 to FLAT =5

PiperOrigin-RevId: 382326710
GitOrigin-RevId: 1620e8ffaa93ef24510ca60c7fff2a07248ac9f6
Change-Id: Ia8f99dde3874808f56062bd37ab3e63764099734

1 files changed, 2 insertions, 116 deletions

diff --git a/absl/strings/internal/cord_rep_ring.cc b/absl/strings/internal/cord_rep_ring.cc
index f78c94e1..20a6fc2b 100644
--- a/absl/strings/internal/cord_rep_ring.cc
+++ b/absl/strings/internal/cord_rep_ring.cc
@@ -26,6 +26,7 @@
 #include "absl/base/macros.h"
 #include "absl/container/inlined_vector.h"
 #include "absl/strings/internal/cord_internal.h"
+#include "absl/strings/internal/cord_rep_consume.h"
 #include "absl/strings/internal/cord_rep_flat.h"
 
 namespace absl {
@@ -49,14 +50,6 @@ inline void CheckCapacity(size_t n, size_t extra) {
   }
 }
 
-// Removes a reference from `rep` only.
-// Asserts that the refcount after decrement is not zero.
-inline bool UnrefNeverOne(CordRep* rep) {
-  bool result = rep->refcount.Decrement();
-  assert(result);
-  return result;
-}
-
 // Creates a flat from the provided string data, allocating up to `extra`
 // capacity in the returned flat depending on kMaxFlatLength limitations.
 // Requires `len` to be less or equal to `kMaxFlatLength`
@@ -68,40 +61,6 @@ CordRepFlat* CreateFlat(const char* s, size_t n, size_t extra = 0) {  // NOLINT
   return rep;
 }
 
-// Unrefs the provided `substring`, and returns `substring->child`
-// Adds or assumes a reference on `substring->child`
-CordRep* ClipSubstring(CordRepSubstring* substring) {
-  CordRep* child = substring->child;
-  if (substring->refcount.IsOne()) {
-    delete substring;
-  } else {
-    CordRep::Ref(child);
-    if (ABSL_PREDICT_FALSE(!substring->refcount.Decrement())) {
-      UnrefNeverOne(child);
-      delete substring;
-    }
-  }
-  return child;
-}
-
-// Unrefs the provided `concat`, and returns `{concat->left, concat->right}`
-// Adds or assumes a reference on `concat->left` and `concat->right`.
-std::pair<CordRep*, CordRep*> ClipConcat(CordRepConcat* concat) {
-  auto result = std::make_pair(concat->left, concat->right);
-  if (concat->refcount.IsOne()) {
-    delete concat;
-  } else {
-    CordRep::Ref(result.first);
-    CordRep::Ref(result.second);
-    if (ABSL_PREDICT_FALSE(!concat->refcount.Decrement())) {
-      UnrefNeverOne(result.first);
-      UnrefNeverOne(result.second);
-      delete concat;
-    }
-  }
-  return result;
-}
-
 // Unrefs the entries in `[head, tail)`.
 // Requires all entries to be a FLAT or EXTERNAL node.
 void UnrefEntries(const CordRepRing* rep, index_type head, index_type tail) {
@@ -117,79 +76,6 @@ void UnrefEntries(const CordRepRing* rep, index_type head, index_type tail) {
   });
 }
 
-template <typename F>
-void Consume(Direction direction, CordRep* rep, F&& fn) {
-  size_t offset = 0;
-  size_t length = rep->length;
-  struct Entry {
-    CordRep* rep;
-    size_t offset;
-    size_t length;
-  };
-  absl::InlinedVector<Entry, 40> stack;
-
-  for (;;) {
-    if (rep->tag >= FLAT || rep->tag == EXTERNAL || rep->tag == RING) {
-      fn(rep, offset, length);
-      if (stack.empty()) return;
-
-      rep = stack.back().rep;
-      offset = stack.back().offset;
-      length = stack.back().length;
-      stack.pop_back();
-    } else if (rep->tag == SUBSTRING) {
-      offset += rep->substring()->start;
-      rep = ClipSubstring(rep->substring());
-    } else if (rep->tag == CONCAT) {
-      auto res = ClipConcat(rep->concat());
-      CordRep* left = res.first;
-      CordRep* right = res.second;
-
-      if (left->length <= offset) {
-        // Don't need left node
-        offset -= left->length;
-        CordRep::Unref(left);
-        rep = right;
-        continue;
-      }
-
-      size_t length_left = left->length - offset;
-      if (length_left >= length) {
-        // Don't need right node
-        CordRep::Unref(right);
-        rep = left;
-        continue;
-      }
-
-      // Need both nodes
-      size_t length_right = length - length_left;
-      if (direction == Direction::kReversed) {
-        stack.push_back({left, offset, length_left});
-        rep = right;
-        offset = 0;
-        length = length_right;
-      } else {
-        stack.push_back({right, 0, length_right});
-        rep = left;
-        length = length_left;
-      }
-    } else {
-      assert("Valid tag" == nullptr);
-      return;
-    }
-  }
-}
-
-template <typename F>
-void Consume(CordRep* rep, F&& fn) {
-  return Consume(Direction::kForward, rep, std::forward<F>(fn));
-}
-
-template <typename F>
-void RConsume(CordRep* rep, F&& fn) {
-  return Consume(Direction::kReversed, rep, std::forward<F>(fn));
-}
-
 }  // namespace
 
 std::ostream& operator<<(std::ostream& s, const CordRepRing& rep) {
@@ -581,7 +467,7 @@ CordRepRing* CordRepRing::Append(CordRepRing* rep, CordRep* child) {
 }
 
 CordRepRing* CordRepRing::PrependSlow(CordRepRing* rep, CordRep* child) {
-  RConsume(child, [&](CordRep* child_arg, size_t offset, size_t len) {
+  ReverseConsume(child, [&](CordRep* child_arg, size_t offset, size_t len) {
     if (IsFlatOrExternal(child_arg)) {
       rep = PrependLeaf(rep, child_arg, offset, len);
     } else {