Re-land "Add LazyCallGraph API to add function to RefSCC"

This re-commits https://reviews.llvm.org/D70927, which I reverted in
https://reviews.llvm.org/rG28213680b2a7d1fdeea16aa3f3a368879472c72a due
to a buildbot error:
http://lab.llvm.org:8011/builders/clang-cmake-x86_64-avx2-linux/builds/13251

I no longer include a test case that appears to crash when built with the
buildbot's compiler, GCC 5.4.0.

1 files changed, 42 insertions, 0 deletions

diff --git a/llvm/unittests/Analysis/LazyCallGraphTest.cpp b/llvm/unittests/Analysis/LazyCallGraphTest.cpp
index 3be4636..a507367 100644
--- a/llvm/unittests/Analysis/LazyCallGraphTest.cpp
+++ b/llvm/unittests/Analysis/LazyCallGraphTest.cpp
@@ -2210,4 +2210,46 @@ TEST(LazyCallGraphTest, RemoveFunctionWithSpurriousRef) {
   EXPECT_EQ(&RC2, &*I++);
   EXPECT_EQ(CG.postorder_ref_scc_end(), I);
 }
+
+TEST(LazyCallGraphTest, AddNewFunctionIntoRefSCC) {
+  LLVMContext Context;
+  // Build and populate a graph composed of a single, self-referential node.
+  std::unique_ptr<Module> M = parseAssembly(Context, "define void @f() {\n"
+                                                     "entry:\n"
+                                                     "  call void @f()\n"
+                                                     "  ret void\n"
+                                                     "}\n");
+  LazyCallGraph CG = buildCG(*M);
+  CG.buildRefSCCs();
+
+  // At this point 'f' is in the call graph.
+  auto &F = lookupFunction(*M, "f");
+  LazyCallGraph::Node *FN = CG.lookup(F);
+  EXPECT_NE(FN, nullptr);
+
+  // And it has an SCC, of course.
+  auto *FSCC = CG.lookupSCC(*FN);
+  EXPECT_NE(FSCC, nullptr);
+
+  // Now, create a new function 'g'.
+  auto *G = Function::Create(F.getFunctionType(), F.getLinkage(),
+                             F.getAddressSpace(), "g", F.getParent());
+  BasicBlock::Create(F.getParent()->getContext(), "entry", G);
+
+  // Instruct the LazyCallGraph to create a new node for 'g', within the same
+  // RefSCC as 'f', but in a separate SCC.
+  CG.addNewFunctionIntoRefSCC(*G, FSCC->getOuterRefSCC());
+
+  // 'g' should now be in the call graph.
+  LazyCallGraph::Node *GN = CG.lookup(*G);
+  EXPECT_NE(GN, nullptr);
+  // 'g' should have an SCC, composed of the singular node 'g'.
+  // ('f' should not be included in the 'g' SCC.)
+  LazyCallGraph::SCC *GSCC = CG.lookupSCC(*GN);
+  EXPECT_NE(GSCC, nullptr);
+  EXPECT_EQ(GSCC->size(), 1);
+  EXPECT_NE(GSCC, FSCC);
+  // 'g' and 'f' should be part of the same RefSCC.
+  EXPECT_EQ(&GSCC->getOuterRefSCC(), &FSCC->getOuterRefSCC());
+}
 }