1 files changed, 25 insertions, 15 deletions
diff --git a/third_party/abseil-cpp/absl/random/gaussian_distribution_test.cc b/third_party/abseil-cpp/absl/random/gaussian_distribution_test.cc
index c0bac2b0db..49c07513bf 100644
--- a/third_party/abseil-cpp/absl/random/gaussian_distribution_test.cc
+++ b/third_party/abseil-cpp/absl/random/gaussian_distribution_test.cc
@@ -21,14 +21,12 @@
 #include <iterator>
 #include <random>
 #include <string>
-#include <type_traits>
 #include <vector>
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/macros.h"
-#include "absl/numeric/internal/representation.h"
 #include "absl/random/internal/chi_square.h"
 #include "absl/random/internal/distribution_test_util.h"
 #include "absl/random/internal/sequence_urbg.h"
@@ -45,15 +43,7 @@ using absl::random_internal::kChiSquared;
 template <typename RealType>
 class GaussianDistributionInterfaceTest : public ::testing::Test {};
 
-// double-double arithmetic is not supported well by either GCC or Clang; see
-// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99048,
-// https://bugs.llvm.org/show_bug.cgi?id=49131, and
-// https://bugs.llvm.org/show_bug.cgi?id=49132. Don't bother running these tests
-// with double doubles until compiler support is better.
-using RealTypes =
-    std::conditional<absl::numeric_internal::IsDoubleDouble(),
-                     ::testing::Types<float, double>,
-                     ::testing::Types<float, double, long double>>::type;
+using RealTypes = ::testing::Types<float, double, long double>;
 TYPED_TEST_CASE(GaussianDistributionInterfaceTest, RealTypes);
 
 TYPED_TEST(GaussianDistributionInterfaceTest, SerializeTest) {
@@ -139,6 +129,29 @@ TYPED_TEST(GaussianDistributionInterfaceTest, SerializeTest) {
 
         ss >> after;
 
+#if defined(__powerpc64__) || defined(__PPC64__) || defined(__powerpc__) || \
+    defined(__ppc__) || defined(__PPC__)
+        if (std::is_same<TypeParam, long double>::value) {
+          // Roundtripping floating point values requires sufficient precision
+          // to reconstruct the exact value.  It turns out that long double
+          // has some errors doing this on ppc, particularly for values
+          // near {1.0 +/- epsilon}.
+          if (mean <= std::numeric_limits<double>::max() &&
+              mean >= std::numeric_limits<double>::lowest()) {
+            EXPECT_EQ(static_cast<double>(before.mean()),
+                      static_cast<double>(after.mean()))
+                << ss.str();
+          }
+          if (stddev <= std::numeric_limits<double>::max() &&
+              stddev >= std::numeric_limits<double>::lowest()) {
+            EXPECT_EQ(static_cast<double>(before.stddev()),
+                      static_cast<double>(after.stddev()))
+                << ss.str();
+          }
+          continue;
+        }
+#endif
+
         EXPECT_EQ(before.mean(), after.mean());
         EXPECT_EQ(before.stddev(), after.stddev())  //
             << ss.str() << " "                      //
@@ -200,10 +213,7 @@ class GaussianDistributionTests : public testing::TestWithParam<Param>,
   template <typename D>
   double SingleChiSquaredTest();
 
-  // We use a fixed bit generator for distribution accuracy tests.  This allows
-  // these tests to be deterministic, while still testing the qualify of the
-  // implementation.
-  absl::random_internal::pcg64_2018_engine rng_{0x2B7E151628AED2A6};
+  absl::InsecureBitGen rng_;
 };
 
 template <typename D>