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[Core] Fix parallel_for for Linux

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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
This commit is contained in:
James Henderson 2017-04-07 08:11:28 +00:00
parent 33e0dbcc58
commit 8abda20a9f
2 changed files with 16 additions and 2 deletions
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3
lld/include/lld/Core/Parallel.h
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@ -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)

15
lld/unittests/CoreTests/ParallelTest.cpp
View File

@ -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);
}