From: Benjamin Barenblat Date: Fri, 27 May 2022 20:58:38 +0000 (+0100) Subject: Skip floating-point edge-case tests when using an x87 X-Git-Tag: archive/raspbian/0_20210324.2-4+rpi1^2~12 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=4d043c73fb4b8a3674b5093d058d056d7922a8a0;p=abseil.git Skip floating-point edge-case tests when using an x87 Forwarded: yes Applied-Upstream: https://github.com/abseil/abseil-cpp/commit/311bbd2e50ea35e921a08186840d3b6ca279e880 32-bit Intel CPUs use 80-bit floats for intermediate values, which can change the results of floating point computations from what we normally expect. Identify tests that are sensitive to the x87, and skip them when we’re on 32-bit Intel. The author works at Google. Upstream applied this patch as Piper revision 378722613 and exported it to GitHub; the Applied-Upstream URL above points to the exported commit. Gbp-Pq: Name float-tests-disable-i386.diff --- diff --git a/absl/random/beta_distribution_test.cc b/absl/random/beta_distribution_test.cc index 44cdfdd..d980c96 100644 --- a/absl/random/beta_distribution_test.cc +++ b/absl/random/beta_distribution_test.cc @@ -15,6 +15,7 @@ #include "absl/random/beta_distribution.h" #include +#include #include #include #include @@ -558,6 +559,14 @@ TEST(BetaDistributionTest, StabilityTest) { // dependencies of the distribution change, such as RandU64ToDouble, then this // is also likely to change. TEST(BetaDistributionTest, AlgorithmBounds) { +#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0 + // We're using an x87-compatible FPU, and intermediate operations are + // performed with 80-bit floats. This produces slightly different results from + // what we expect below. + GTEST_SKIP() + << "Skipping the test because we detected x87 floating-point semantics"; +#endif + { absl::random_internal::sequence_urbg urbg( {0x7fbe76c8b4395800ull, 0x8000000000000000ull}); diff --git a/absl/random/distributions_test.cc b/absl/random/distributions_test.cc index 5866a07..d3a5dd7 100644 --- a/absl/random/distributions_test.cc +++ b/absl/random/distributions_test.cc @@ -14,6 +14,7 @@ #include "absl/random/distributions.h" +#include #include #include #include @@ -224,6 +225,15 @@ TEST_F(RandomDistributionsTest, UniformNoBounds) { TEST_F(RandomDistributionsTest, UniformNonsenseRanges) { // The ranges used in this test are undefined behavior. // The results are arbitrary and subject to future changes. + +#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0 + // We're using an x87-compatible FPU, and intermediate operations can be + // performed with 80-bit floats. This produces slightly different results from + // what we expect below. + GTEST_SKIP() + << "Skipping the test because we detected x87 floating-point semantics"; +#endif + absl::InsecureBitGen gen; // diff --git a/absl/random/exponential_distribution_test.cc b/absl/random/exponential_distribution_test.cc index af11d61..81a5d17 100644 --- a/absl/random/exponential_distribution_test.cc +++ b/absl/random/exponential_distribution_test.cc @@ -15,6 +15,7 @@ #include "absl/random/exponential_distribution.h" #include +#include #include #include #include @@ -384,6 +385,15 @@ TEST(ExponentialDistributionTest, StabilityTest) { TEST(ExponentialDistributionTest, AlgorithmBounds) { // Relies on absl::uniform_real_distribution, so some of these comments // reference that. + +#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0 + // We're using an x87-compatible FPU, and intermediate operations can be + // performed with 80-bit floats. This produces slightly different results from + // what we expect below. + GTEST_SKIP() + << "Skipping the test because we detected x87 floating-point semantics"; +#endif + absl::exponential_distribution dist; { diff --git a/absl/random/uniform_real_distribution_test.cc b/absl/random/uniform_real_distribution_test.cc index 18bcd3b..035bd28 100644 --- a/absl/random/uniform_real_distribution_test.cc +++ b/absl/random/uniform_real_distribution_test.cc @@ -14,6 +14,7 @@ #include "absl/random/uniform_real_distribution.h" +#include #include #include #include @@ -70,6 +71,14 @@ using RealTypes = TYPED_TEST_SUITE(UniformRealDistributionTest, RealTypes); TYPED_TEST(UniformRealDistributionTest, ParamSerializeTest) { +#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0 + // We're using an x87-compatible FPU, and intermediate operations are + // performed with 80-bit floats. This produces slightly different results from + // what we expect below. + GTEST_SKIP() + << "Skipping the test because we detected x87 floating-point semantics"; +#endif + using param_type = typename absl::uniform_real_distribution::param_type; diff --git a/absl/time/duration_test.cc b/absl/time/duration_test.cc index a3617e7..b7209e1 100644 --- a/absl/time/duration_test.cc +++ b/absl/time/duration_test.cc @@ -17,6 +17,7 @@ #endif #include // NOLINT(build/c++11) +#include #include #include #include @@ -1390,6 +1391,14 @@ void VerifyApproxSameAsMul(double time_as_seconds, int* const misses) { // Seconds(point) returns a duration near point * Seconds(1.0). (They may // not be exactly equal due to fused multiply/add contraction.) TEST(Duration, ToDoubleSecondsCheckEdgeCases) { +#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0 + // We're using an x87-compatible FPU, and intermediate operations can be + // performed with 80-bit floats. This means the edge cases are different than + // what we expect here, so just skip this test. + GTEST_SKIP() + << "Skipping the test because we detected x87 floating-point semantics"; +#endif + constexpr uint32_t kTicksPerSecond = absl::time_internal::kTicksPerSecond; constexpr auto duration_tick = absl::time_internal::MakeDuration(0, 1u); int misses = 0;