gnu: abseil-cpp-20200923.3: Fix test suite on some architectures.

* gnu/packages/cpp.scm (abseil-cpp-20200923.3)[source]: Add patches.
* gnu/packages/patches/abseil-cpp-20200923.3-adjust-sysinfo.patch,
gnu/packages/patches/abseil-cpp-20200923.3-duration-test.patch: New
files.
* gnu/local.mk (dist_patch_DATA): Register them.

Change-Id: I3a0a6c3396a7c2854236c68ec77a68bbdd6af1f4

1 files changed, 86 insertions, 0 deletions

diff --git a/gnu/packages/patches/abseil-cpp-20200923.3-duration-test.patch b/gnu/packages/patches/abseil-cpp-20200923.3-duration-test.patch
new file mode 100644
index 0000000000..9609c2588b
--- /dev/null
+++ b/gnu/packages/patches/abseil-cpp-20200923.3-duration-test.patch
@@ -0,0 +1,86 @@
+This patch is taken from upstream and helps the test pass on all architectures.
+
+The adjustment to absl/numeric/internal/bits.h was removed since the file
+didn't appear in the git checkout.
+
+From b0735979d778a768caee207f01f327535cbd2140 Mon Sep 17 00:00:00 2001
+From: Abseil Team <[email protected]>
+Date: Tue, 2 Mar 2021 14:28:07 -0800
+Subject: [PATCH] Export of internal Abseil changes
+
+--
+a74bdb72c3a6983e08a805938dd0e20e97d55bba by Abseil Team <[email protected]>:
+
+Fix typo: calcualte -> calculate
+
+PiperOrigin-RevId: 360515509
+
+--
+3ddf8ac194e81a13e9de095e59dd061c1beacfe3 by Benjamin Barenblat <[email protected]>:
+
+Make tests tolerant of FMA contraction
+
+Weaken Duration.ToDoubleSecondsCheckEdgeCases and
+Duration.ToDoubleSecondsCheckRandom to make them less sensitive to fused
+multiply/add contraction.
+
+PiperOrigin-RevId: 360297653
+GitOrigin-RevId: a74bdb72c3a6983e08a805938dd0e20e97d55bba
+Change-Id: I0c55383bc13040ea77511c4130d142368103dc57
+---
+ absl/numeric/internal/bits.h |  2 +-
+ absl/time/duration_test.cc   | 18 +++++++++++-------
+ 2 files changed, 12 insertions(+), 8 deletions(-)
+
+diff --git a/absl/time/duration_test.cc b/absl/time/duration_test.cc
+index 4d85a2c4f45..fb28fa987f6 100644
+--- a/absl/time/duration_test.cc
++++ b/absl/time/duration_test.cc
+@@ -1369,10 +1369,13 @@ TEST(Duration, SmallConversions) {
+   EXPECT_THAT(ToTimeval(absl::Nanoseconds(2000)), TimevalMatcher(tv));
+ }
+ 
+-void VerifySameAsMul(double time_as_seconds, int* const misses) {
++void VerifyApproxSameAsMul(double time_as_seconds, int* const misses) {
+   auto direct_seconds = absl::Seconds(time_as_seconds);
+   auto mul_by_one_second = time_as_seconds * absl::Seconds(1);
+-  if (direct_seconds != mul_by_one_second) {
++  // These are expected to differ by up to one tick due to fused multiply/add
++  // contraction.
++  if (absl::AbsDuration(direct_seconds - mul_by_one_second) >
++      absl::time_internal::MakeDuration(0, 1u)) {
+     if (*misses > 10) return;
+     ASSERT_LE(++(*misses), 10) << "Too many errors, not reporting more.";
+     EXPECT_EQ(direct_seconds, mul_by_one_second)
+@@ -1384,7 +1387,8 @@ void VerifySameAsMul(double time_as_seconds, int* const misses) {
+ // For a variety of interesting durations, we find the exact point
+ // where one double converts to that duration, and the very next double
+ // converts to the next duration.  For both of those points, verify that
+-// Seconds(point) returns the same duration as point * Seconds(1.0)
++// 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) {
+   constexpr uint32_t kTicksPerSecond = absl::time_internal::kTicksPerSecond;
+   constexpr auto duration_tick = absl::time_internal::MakeDuration(0, 1u);
+@@ -1423,8 +1427,8 @@ TEST(Duration, ToDoubleSecondsCheckEdgeCases) {
+         }
+         // Now low_edge is the highest double that converts to Duration d,
+         // and high_edge is the lowest double that converts to Duration after_d.
+-        VerifySameAsMul(low_edge, &misses);
+-        VerifySameAsMul(high_edge, &misses);
++        VerifyApproxSameAsMul(low_edge, &misses);
++        VerifyApproxSameAsMul(high_edge, &misses);
+       }
+     }
+   }
+@@ -1444,8 +1448,8 @@ TEST(Duration, ToDoubleSecondsCheckRandom) {
+   int misses = 0;
+   for (int i = 0; i < 1000000; ++i) {
+     double d = std::exp(uniform(gen));
+-    VerifySameAsMul(d, &misses);
+-    VerifySameAsMul(-d, &misses);
++    VerifyApproxSameAsMul(d, &misses);
++    VerifyApproxSameAsMul(-d, &misses);
+   }
+ }
+