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, 13 insertions, 7 deletions

diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index 1e2436ba..bddc9815 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -150,22 +150,24 @@ struct CordRepExternal;
 struct CordRepFlat;
 struct CordRepSubstring;
 class CordRepRing;
+class CordRepBtree;
 
 // Various representations that we allow
 enum CordRepKind {
   CONCAT = 0,
   SUBSTRING = 1,
-  RING = 2,
-  EXTERNAL = 3,
+  BTREE = 2,
+  RING = 3,
+  EXTERNAL = 4,
 
   // We have different tags for different sized flat arrays,
-  // starting with FLAT, and limited to MAX_FLAT_TAG. The 224 value is based on
+  // starting with FLAT, and limited to MAX_FLAT_TAG. The 225 value is based on
   // the current 'size to tag' encoding of 8 / 32 bytes. If a new tag is needed
   // in the future, then 'FLAT' and 'MAX_FLAT_TAG' should be adjusted as well
   // as the Tag <---> Size logic so that FLAT stil represents the minimum flat
   // allocation size. (32 bytes as of now).
-  FLAT = 4,
-  MAX_FLAT_TAG = 224
+  FLAT = 5,
+  MAX_FLAT_TAG = 225
 };
 
 // There are various locations where we want to check if some rep is a 'plain'
@@ -175,8 +177,9 @@ enum CordRepKind {
 // so likewise align RING to EXTERNAL.
 // Note that we can leave this optimization to the compiler. The compiler will
 // DTRT when it sees a condition like `tag == EXTERNAL || tag >= FLAT`.
-static_assert(EXTERNAL == RING + 1, "RING and EXTERNAL values not consecutive");
-static_assert(FLAT == EXTERNAL + 1, "EXTERNAL and FLAT values not consecutive");
+static_assert(RING == BTREE + 1, "BTREE and RING not consecutive");
+static_assert(EXTERNAL == RING + 1, "BTREE and EXTERNAL not consecutive");
+static_assert(FLAT == EXTERNAL + 1, "EXTERNAL and FLAT not consecutive");
 
 struct CordRep {
   CordRep() = default;
@@ -203,6 +206,9 @@ struct CordRep {
   inline CordRepFlat* flat();
   inline const CordRepFlat* flat() const;
 
+  inline CordRepBtree* btree();
+  inline const CordRepBtree* btree() const;
+
   // --------------------------------------------------------------------
   // Memory management