Initialize LLVM time trace profiler on each code generation thread

In https://reviews.llvm.org/D71059 LLVM 11, the time trace profiler was
extended to support multiple threads.

`timeTraceProfilerInitialize` creates a thread local profiler instance.
When a thread finishes `timeTraceProfilerFinishThread` moves a thread
local instance into a global collection of instances. Finally when all
codegen work is complete `timeTraceProfilerWrite` writes data from the
current thread local instance and the instances in global collection
of instances.

Previously, the profiler was intialized on a single thread only. Since
this thread performs no code generation on its own, the resulting
profile was empty.

Update LLVM codegen to initialize & finish time trace profiler on each
code generation thread.

1 files changed, 0 insertions, 5 deletions

diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index 246bb88885d..34c28938c85 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -113,11 +113,6 @@ unsafe fn configure_llvm(sess: &Session) {
     }
 
     if sess.opts.debugging_opts.llvm_time_trace {
-        // time-trace is not thread safe and running it in parallel will cause seg faults.
-        if !sess.opts.debugging_opts.no_parallel_llvm {
-            bug!("`-Z llvm-time-trace` requires `-Z no-parallel-llvm")
-        }
-
         llvm::LLVMTimeTraceProfilerInitialize();
     }