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

[vsapsai]

Summary

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.

[tejohnson]

LGTM
Thanks!

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

for (const Instruction &I : BB) {
         // aliasee.
         CallGraphEdges[Index.getOrInsertValueInfo(
                            cast<GlobalValue>(CalledValue))]
             .updateHotness(Hotness);
       } else {
         // 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;
         auto CandidateProfileData =
             ICallAnalysis.getPromotionCandidatesForInstruction(
                 &I, NumVals, TotalCount, NumCandidates);
         for (auto &Candidate : CandidateProfileData)
           CallGraphEdges[Index.getOrInsertValueInfo(Candidate.Value)]

llvm/test/Bitcode/thinlto-function-summary-callgraph-cast.ll

 ; Test to check the callgraph for calls to casts.
 ; RUN: opt -module-summary %s -o %t.o
 ; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
 ; PR34966
 
 ; CHECK:       <GLOBALVAL_SUMMARY_BLOCK
 ; CHECK-NEXT:    <VERSION
-; "op7=1" is a call to "callee" function.
-; CHECK-NEXT:    <PERMODULE {{.*}} op7=1 op8=[[ALIASID:[0-9]+]]/>
+; "op7" is a call to "callee" function.
+; CHECK-NEXT:    <PERMODULE {{.*}} op7=3 op8=[[ALIASID:[0-9]+]]/>
+; "another_caller" has only references but no calls.
+; CHECK-NEXT:    <PERMODULE {{.*}} op4=3 {{.*}} op7={{[0-9]+}}/>
 ; CHECK-NEXT:    <PERMODULE {{.*}} op0=[[ALIASEEID:[0-9]+]]
 ; CHECK-NEXT:    <ALIAS {{.*}} op0=[[ALIASID]] {{.*}} op2=[[ALIASEEID]]/>
 ; CHECK-NEXT:  </GLOBALVAL_SUMMARY_BLOCK>
 
 ; ModuleID = 'thinlto-function-summary-callgraph-cast.ll'
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @caller() {
     call void bitcast (void (...)* @callee to void ()*)()
     call void bitcast (void (...)* @analias to void ()*)()
     ret void
 }
 
+define void @another_caller() {
+    ; Test calls that aren't handled either as direct or indirect.
+    call void select (i1 icmp eq (i32* @global, i32* null), void ()* @f, void ()* @g)()
+    ret void
+}
+
 declare void @callee(...)
 
 @analias = alias void (...), bitcast (void ()* @aliasee to void (...)*)
 
 define void @aliasee() {
 entry:
     ret void
 }
+
+declare void @f()
+declare void @g()
+@global = extern_weak global i32