From 8abda20a9f23b45d2dca76932cfd1c723db3ee72 Mon Sep 17 00:00:00 2001 From: James Henderson Date: Fri, 7 Apr 2017 08:11:28 +0000 Subject: [PATCH] [Core] Fix parallel_for for Linux r299635 exposed a latent bug in the Linux implementation of parallel_for, which resulted in it calling the function outside of the range requested, resulting later in a segmentation fault. This change fixes this issue and adds a unit test. llvm-svn: 299748 --- lld/include/lld/Core/Parallel.h | 3 +-- lld/unittests/CoreTests/ParallelTest.cpp | 15 +++++++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/lld/include/lld/Core/Parallel.h b/lld/include/lld/Core/Parallel.h index f241453..64b4f2a 100644 --- a/lld/include/lld/Core/Parallel.h +++ b/lld/include/lld/Core/Parallel.h @@ -318,12 +318,11 @@ void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) { TaskGroup Tg; IndexTy I = Begin; - for (; I < End; I += TaskSize) { + for (; I + TaskSize < End; I += TaskSize) { Tg.spawn([=, &Fn] { for (IndexTy J = I, E = I + TaskSize; J != E; ++J) Fn(J); }); - Begin += TaskSize; } Tg.spawn([=, &Fn] { for (IndexTy J = I; J < End; ++J) diff --git a/lld/unittests/CoreTests/ParallelTest.cpp b/lld/unittests/CoreTests/ParallelTest.cpp index c028243..f02db92 100644 --- a/lld/unittests/CoreTests/ParallelTest.cpp +++ b/lld/unittests/CoreTests/ParallelTest.cpp @@ -29,3 +29,18 @@ TEST(Parallel, sort) { lld::parallel_sort(std::begin(array), std::end(array)); ASSERT_TRUE(std::is_sorted(std::begin(array), std::end(array))); } + +TEST(Parallel, parallel_for) { + // We need to test the case with a TaskSize > 1. We are white-box testing + // here. The TaskSize is calculated as (End - Begin) / 1024 at the time of + // writing. + uint32_t range[2050]; + std::fill(range, range + 2050, 1); + lld::parallel_for(0, 2049, [&range](size_t I) { ++range[I]; }); + + uint32_t expected[2049]; + std::fill(expected, expected + 2049, 2); + ASSERT_TRUE(std::equal(range, range + 2049, expected)); + // Check that we don't write past the end of the requested range. + ASSERT_EQ(range[2049], 1); +} -- 2.7.4