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

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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

1 files changed, 3 insertions, 20 deletions

diff --git a/absl/random/internal/fastmath.h b/absl/random/internal/fastmath.h
index 6baeb5a7..963b7690 100644
--- a/absl/random/internal/fastmath.h
+++ b/absl/random/internal/fastmath.h
@@ -22,27 +22,22 @@
 #include <cmath>
 #include <cstdint>
 
-#include "absl/base/internal/bits.h"
+#include "absl/numeric/bits.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace random_internal {
 
-// Returns the position of the first bit set.
-inline int LeadingSetBit(uint64_t n) {
-  return 64 - base_internal::CountLeadingZeros64(n);
-}
-
 // Compute log2(n) using integer operations.
 // While std::log2 is more accurate than std::log(n) / std::log(2), for
 // very large numbers--those close to std::numeric_limits<uint64_t>::max() - 2,
 // for instance--std::log2 rounds up rather than down, which introduces
 // definite skew in the results.
 inline int IntLog2Floor(uint64_t n) {
-  return (n <= 1) ? 0 : (63 - base_internal::CountLeadingZeros64(n));
+  return (n <= 1) ? 0 : (63 - countl_zero(n));
 }
 inline int IntLog2Ceil(uint64_t n) {
-  return (n <= 1) ? 0 : (64 - base_internal::CountLeadingZeros64(n - 1));
+  return (n <= 1) ? 0 : (64 - countl_zero(n - 1));
 }
 
 inline double StirlingLogFactorial(double n) {
@@ -55,18 +50,6 @@ inline double StirlingLogFactorial(double n) {
          (1.0 / 360.0) * ninv * ninv * ninv;
 }
 
-// Rotate value right.
-//
-// We only implement the uint32_t / uint64_t versions because
-// 1) those are the only ones we use, and
-// 2) those are the only ones where clang detects the rotate idiom correctly.
-inline constexpr uint32_t rotr(uint32_t value, uint8_t bits) {
-  return (value >> (bits & 31)) | (value << ((-bits) & 31));
-}
-inline constexpr uint64_t rotr(uint64_t value, uint8_t bits) {
-  return (value >> (bits & 63)) | (value << ((-bits) & 63));
-}
-
 }  // namespace random_internal
 ABSL_NAMESPACE_END
 }  // namespace absl