[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

1 files changed, 1 insertions, 2 deletions

diff --git a/lld/include/lld/Core/Parallel.h b/lld/include/lld/Core/Parallel.h
index f241453a4d3..64b4f2ab04d 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)