Add function entry counts from sample profiles.

This patch uses the new function profile metadata "function_entry_count"
to annotate entry counts from sample profiles.

In a sampling profile, the total samples collected at the function entry
are an approximation for the number of times that function was invoked.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237265 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/SampleProfile.cpp

@@ -580,6 +580,10 @@ void SampleProfileLoader::propagateWeights(Function &F) {
   bool Changed = true;
   unsigned i = 0;
 
+  // Add an entry count to the function using the samples gathered
+  // at the function entry.
+  F.setEntryCount(Samples->getHeadSamples());
+
   // Before propagation starts, build, for each block, a list of
   // unique predecessors and successors. This is necessary to handle
   // identical edges in multiway branches. Since we visit all blocks and all