[ThinLTO] Remove too aggressive assertion in building function call graph.

The assertion was introduced in r317853 but there are cases when a call
isn't handled either as direct or indirect. In this case we add a
reference graph edge but not a call graph edge.

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, eraman, hiraditya, efriedma, llvm-commits

Differential Revision: https://reviews.llvm.org/D40056

llvm-svn: 318540

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

@@ -280,8 +280,9 @@ computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
         // Skip inline assembly calls.
         if (CI && CI->isInlineAsm())
           continue;
-        assert(CalledValue && !isa<Constant>(CalledValue) &&
-               "Expected indirect call");
+        // Skip direct calls.
+        if (!CalledValue || isa<Constant>(CalledValue))
+          continue;
 
         uint32_t NumVals, NumCandidates;
         uint64_t TotalCount;