ftime-trace: Trace loop passes

These can take a significant amount of time in some builds.

Suggested by Andrea Di Biagio.

Differential Revision: https://reviews.llvm.org/D62666

llvm-svn: 362219
diff --git a/llvm/lib/Analysis/LoopPass.cpp b/llvm/lib/Analysis/LoopPass.cpp
index c57ec2a..4ab3798 100644
--- a/llvm/lib/Analysis/LoopPass.cpp
+++ b/llvm/lib/Analysis/LoopPass.cpp
@@ -22,6 +22,7 @@
 #include "llvm/IR/PassTimingInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Timer.h"
+#include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
@@ -209,6 +210,8 @@
     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
       LoopPass *P = getContainedPass(Index);
 
+      llvm::TimeTraceScope LoopPassScope("RunLoopPass", P->getPassName());
+
       dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
                    CurrentLoop->getHeader()->getName());
       dumpRequiredSet(P);