Export of internal Abseil changes

--
dab5caab05d89d03066ef92584660688595a3aaf by Mark Barolak <mbar@google.com>:

Add absl::Status and absl::StatusOr to absl/README.md

Import of https://github.com/abseil/abseil-cpp/pull/863

PiperOrigin-RevId: 347857368

--
1ca3c7a96417cd6e6d62f4dc36fd5ddaa61cfa20 by Chris Kennelly <ckennelly@google.com>:

Leverage integer power-of-2 functions and bit counting library in Abseil.

PiperOrigin-RevId: 347816486

--
e5cbe05879fd65dce7875e2e0105331a1615d89b by Chris Kennelly <ckennelly@google.com>:

Mitigate narrowing warning on MSVC.

If sizeof(x) <= sizeof(uint32_t), no truncation occurs when casting to
uint32_t, but the compiler cannot always determine this.

PiperOrigin-RevId: 347696526

--
079dff64cb175d282d9e22dfb4a522199ffdae2e by Benjamin Barenblat <bbaren@google.com>:

Avoid libgcc -NaN narrowing bug

When testing -NaN parsing, avoid narrowing -NaN from double to float.
This avoids a bug in libgcc
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98251).

PiperOrigin-RevId: 347654751

--
2e78a7634865aeef6765e1f447e96cf8d9985059 by Chris Kennelly <ckennelly@google.com>:

Mark popcount helpers as inline.

These are conditionally constexpr, so we need to add inline to cover the
non-constexpr builds to avoid ODR violations.

PiperOrigin-RevId: 347620138

--
437fbb363aea1654179f102dcdd607ec33c1af1e by Chris Kennelly <ckennelly@google.com>:

Use explicit narrowing cast.

This is never invoked in practice, but compilers with -Wimplicit-int-conversion
may trigger when sizeof(T) > sizeof(uint16_t) prior to determining this never
runs.

PiperOrigin-RevId: 347609857
GitOrigin-RevId: dab5caab05d89d03066ef92584660688595a3aaf
Change-Id: I6296ddffe7ec646f8ce121138f21e1e85a2cff4b

7 files changed, 20 insertions, 19 deletions

diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 3154d80..7001679 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -69,7 +69,6 @@ cc_library(
     deps = [
         ":internal",
         "//absl/base",
-        "//absl/base:bits",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:endian",
@@ -77,6 +76,7 @@ cc_library(
         "//absl/base:throw_delegate",
         "//absl/memory",
         "//absl/meta:type_traits",
+        "//absl/numeric:bits",
         "//absl/numeric:int128",
     ],
 )
@@ -663,11 +663,11 @@ cc_library(
     visibility = ["//visibility:private"],
     deps = [
         ":strings",
-        "//absl/base:bits",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/functional:function_ref",
         "//absl/meta:type_traits",
+        "//absl/numeric:bits",
         "//absl/numeric:int128",
         "//absl/types:optional",
         "//absl/types:span",
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index fa61ff6..654d0fd 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -56,7 +56,7 @@ absl_cc_library(
   DEPS
     absl::strings_internal
     absl::base
-    absl::internal_bits
+    absl::bits
     absl::config
     absl::core_headers
     absl::endian
@@ -406,7 +406,7 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
-    absl::internal_bits
+    absl::bits
     absl::strings
     absl::config
     absl::core_headers
diff --git a/absl/strings/charconv.cc b/absl/strings/charconv.cc
index 3613a65..b8674c2 100644
--- a/absl/strings/charconv.cc
+++ b/absl/strings/charconv.cc
@@ -20,7 +20,7 @@
 #include <cstring>
 
 #include "absl/base/casts.h"
-#include "absl/base/internal/bits.h"
+#include "absl/numeric/bits.h"
 #include "absl/numeric/int128.h"
 #include "absl/strings/internal/charconv_bigint.h"
 #include "absl/strings/internal/charconv_parse.h"
@@ -242,11 +242,11 @@ struct CalculatedFloat {
 
 // Returns the bit width of the given uint128.  (Equivalently, returns 128
 // minus the number of leading zero bits.)
-int BitWidth(uint128 value) {
+unsigned BitWidth(uint128 value) {
   if (Uint128High64(value) == 0) {
-    return 64 - base_internal::CountLeadingZeros64(Uint128Low64(value));
+    return static_cast<unsigned>(bit_width(Uint128Low64(value)));
   }
-  return 128 - base_internal::CountLeadingZeros64(Uint128High64(value));
+  return 128 - countl_zero(Uint128High64(value));
 }
 
 // Calculates how far to the right a mantissa needs to be shifted to create a
@@ -519,7 +519,7 @@ CalculatedFloat CalculateFromParsedHexadecimal(
     const strings_internal::ParsedFloat& parsed_hex) {
   uint64_t mantissa = parsed_hex.mantissa;
   int exponent = parsed_hex.exponent;
-  int mantissa_width = 64 - base_internal::CountLeadingZeros64(mantissa);
+  auto mantissa_width = static_cast<unsigned>(bit_width(mantissa));
   const int shift = NormalizedShiftSize<FloatType>(mantissa_width, exponent);
   bool result_exact;
   exponent += shift;
diff --git a/absl/strings/charconv_test.cc b/absl/strings/charconv_test.cc
index 9090e9c..b83de5a 100644
--- a/absl/strings/charconv_test.cc
+++ b/absl/strings/charconv_test.cc
@@ -653,7 +653,9 @@ TEST(FromChars, NaNFloats) {
                      negative_from_chars_float);
     EXPECT_TRUE(std::signbit(negative_from_chars_float));
     EXPECT_FALSE(Identical(negative_from_chars_float, from_chars_float));
-    from_chars_float = std::copysign(from_chars_float, -1.0);
+    // Use the (float, float) overload of std::copysign to prevent narrowing;
+    // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98251.
+    from_chars_float = std::copysign(from_chars_float, -1.0f);
     EXPECT_TRUE(Identical(negative_from_chars_float, from_chars_float));
   }
 }
diff --git a/absl/strings/internal/str_format/float_conversion.cc b/absl/strings/internal/str_format/float_conversion.cc
index 0ded0a6..2aa41aa 100644
--- a/absl/strings/internal/str_format/float_conversion.cc
+++ b/absl/strings/internal/str_format/float_conversion.cc
@@ -24,10 +24,10 @@
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/bits.h"
 #include "absl/base/optimization.h"
 #include "absl/functional/function_ref.h"
 #include "absl/meta/type_traits.h"
+#include "absl/numeric/bits.h"
 #include "absl/numeric/int128.h"
 #include "absl/strings/numbers.h"
 #include "absl/types/optional.h"
@@ -315,12 +315,11 @@ class FractionalDigitGenerator {
 };
 
 // Count the number of leading zero bits.
-int LeadingZeros(uint64_t v) { return base_internal::CountLeadingZeros64(v); }
+int LeadingZeros(uint64_t v) { return countl_zero(v); }
 int LeadingZeros(uint128 v) {
   auto high = static_cast<uint64_t>(v >> 64);
   auto low = static_cast<uint64_t>(v);
-  return high != 0 ? base_internal::CountLeadingZeros64(high)
-                   : 64 + base_internal::CountLeadingZeros64(low);
+  return high != 0 ? countl_zero(high) : 64 + countl_zero(low);
 }
 
 // Round up the text digits starting at `p`.
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index 3da1059..e6bf44c 100644
--- a/absl/strings/numbers.cc
+++ b/absl/strings/numbers.cc
@@ -31,8 +31,8 @@
 #include <utility>
 
 #include "absl/base/attributes.h"
-#include "absl/base/internal/bits.h"
 #include "absl/base/internal/raw_logging.h"
+#include "absl/numeric/bits.h"
 #include "absl/strings/ascii.h"
 #include "absl/strings/charconv.h"
 #include "absl/strings/escaping.h"
@@ -303,7 +303,7 @@ static std::pair<uint64_t, uint64_t> Mul32(std::pair<uint64_t, uint64_t> num,
   uint64_t bits128_up = (bits96_127 >> 32) + (bits64_127 < bits64_95);
   if (bits128_up == 0) return {bits64_127, bits0_63};
 
-  int shift = 64 - base_internal::CountLeadingZeros64(bits128_up);
+  auto shift = static_cast<unsigned>(bit_width(bits128_up));
   uint64_t lo = (bits0_63 >> shift) + (bits64_127 << (64 - shift));
   uint64_t hi = (bits64_127 >> shift) + (bits128_up << (64 - shift));
   return {hi, lo};
@@ -334,7 +334,7 @@ static std::pair<uint64_t, uint64_t> PowFive(uint64_t num, int expfive) {
       5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,
       5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5};
   result = Mul32(result, powers_of_five[expfive & 15]);
-  int shift = base_internal::CountLeadingZeros64(result.first);
+  int shift = countl_zero(result.first);
   if (shift != 0) {
     result.first = (result.first << shift) + (result.second >> (64 - shift));
     result.second = (result.second << shift);
diff --git a/absl/strings/numbers.h b/absl/strings/numbers.h
index 2e004b4..7966e25 100644
--- a/absl/strings/numbers.h
+++ b/absl/strings/numbers.h
@@ -37,7 +37,6 @@
 #include <type_traits>
 
 #include "absl/base/config.h"
-#include "absl/base/internal/bits.h"
 #ifdef __SSE4_2__
 // TODO(jorg): Remove this when we figure out the right way
 // to swap bytes on SSE 4.2 that works with the compilers
@@ -48,6 +47,7 @@
 #endif
 #include "absl/base/macros.h"
 #include "absl/base/port.h"
+#include "absl/numeric/bits.h"
 #include "absl/numeric/int128.h"
 #include "absl/strings/string_view.h"
 
@@ -240,7 +240,7 @@ inline size_t FastHexToBufferZeroPad16(uint64_t val, char* out) {
   }
 #endif
   // | 0x1 so that even 0 has 1 digit.
-  return 16 - absl::base_internal::CountLeadingZeros64(val | 0x1) / 4;
+  return 16 - countl_zero(val | 0x1) / 4;
 }
 
 }  // namespace numbers_internal