[PATCH] D152054: [OpenMP] Codegen support for thread_limit on target directive

[Kazushi Marukawa via Phabricator via cfe-commits]

kaz7 added a comment.

I figure out the reason of strange behavior I mentioned last night.  However, I'm still not sure what is the good way to solve this problem.  Can someone check the behavior with `-O2` option please?  Thanks!



================
Comment at: openmp/runtime/test/target/target_thread_limit.cpp:73
+    printf("\nsecond target: thread_limit = %d", omp_get_thread_limit());
+// OMP51: second target: thread_limit = 3
+#pragma omp parallel
----------------
Last night, I cannot use inline comment, but now I can.  So, I'm writing down my comments here.

The problem I mentioned last night was caused by optimization.  This works fine with optimization level by default, but this doesn't work with `-O2` even on x86_64.  I'm using `-O2` for tests, so I come across this problem.  I'll write command lines to reproduce my problem below.  As you see, there is a warning message at `-O2`.  So, this behavior may be expected, though.  In addition, I'm using f8efa65 to produce following results.

```
$ cd build
$ ninja
...
$ ./bin/clang++  -fopenmp -I runtimes/runtimes-x86_64-unknown-linux-gnu-bins/openmp/runtime/src -I ../llvm-project/openmp/runtime/test -L runtimes/runtimes-x86_64-unknown-linux-gnu-bins/openmp/runtime/src -fno-omit-frame-pointer -I ../llvm-project/openmp/runtime/test/ompt -std=c++17 ../llvm-project/openmp/runtime/test/target/target_thread_limit.cpp -o ok -lm -latomic -fopenmp-version=51
$ LD_LIBRARY_PATH=runtimes/runtimes-x86_64-unknown-linux-gnu-bins/openmp/runtime/src ./ok | grep "second target: thread_limit"
second target: thread_limit = 3
$ ./bin/clang++ -fopenmp -I runtimes/runtimes-x86_64-unknown-linux-gnu-bins/openmp/runtime/src -I ../llvm-project/openmp/runtime/test -L runtimes/runtimes-x86_64-unknown-linux-gnu-bins/openmp/runtime/src -fno-omit-frame-pointer -I ../llvm-project/openmp/runtime/test/ompt -std=c++17 ../llvm-project/openmp/runtime/test/target/target_thread_limit.cpp -o bad -lm -latomic -fopenmp-version=51 -O2
warning: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering [-Wpass-failed=transform-warning]
1 warning generated.
$ LD_LIBRARY_PATH=runtimes/runtimes-x86_64-unknown-linux-gnu-bins/openmp/runtime/src ./bad | grep "second target: thread_limit"
second target: thread_limit = 2147483647
```


Repository:
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https://reviews.llvm.org/D152054