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llvm/unittests/Analysis/LazyCallGraphTest.cpp
Chandler Carruth e3a8e534e1 [LCG] Re-organize the methods for mutating a call graph to make their 
API requirements much more obvious.

The key here is that there are two totally different use cases for
mutating the graph. Prior to doing any SCC formation, it is very easy to
mutate the graph. There may be users that want to do small tweaks here,
and then use the already-built graph for their SCC-based operations.
This method remains on the graph itself and is documented carefully as
being cheap but unavailable once SCCs are formed.

Once SCCs are formed, and there is some in-flight DFS building them, we
have to be much more careful in how we mutate the graph. These mutation
operations are sunk onto the SCCs themselves, which both simplifies
things (the code was already there!) and helps make it obvious that
these interfaces are only applicable within that context. The other
primary constraint is that the edge being mutated is actually related to
the SCC on which we call the method. This helps make it obvious that you
cannot arbitrarily mutate some other SCC.

I've tried to write much more complete documentation for the interesting
mutation API -- intra-SCC edge removal. Currently one aspect of this
documentation is a lie (the result list of SCCs) but we also don't even
have tests for that API. =[ I'm going to add tests and fix it to match
the documentation next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207339 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-27 01:59:50 +00:00

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//===- LazyCallGraphTest.cpp - Unit tests for the lazy CG analysis --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/LazyCallGraph.h"
#include "llvm/AsmParser/Parser.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"
#include <memory>
using namespace llvm;
namespace {
std::unique_ptr<Module> parseAssembly(const char *Assembly) {
auto M = make_unique<Module>("Module", getGlobalContext());
SMDiagnostic Error;
bool Parsed =
ParseAssemblyString(Assembly, M.get(), Error, M->getContext()) == M.get();
std::string ErrMsg;
raw_string_ostream OS(ErrMsg);
Error.print("", OS);
// A failure here means that the test itself is buggy.
if (!Parsed)
report_fatal_error(OS.str().c_str());
return M;
}
// IR forming a call graph with a diamond of triangle-shaped SCCs:
//
// d1
// / \
// d3--d2
// / \
// b1 c1
// / \ / \
// b3--b2 c3--c2
// \ /
// a1
// / \
// a3--a2
//
// All call edges go up between SCCs, and clockwise around the SCC.
static const char DiamondOfTriangles[] =
"define void @a1() {\n"
"entry:\n"
" call void @a2()\n"
" call void @b2()\n"
" call void @c3()\n"
" ret void\n"
"}\n"
"define void @a2() {\n"
"entry:\n"
" call void @a3()\n"
" ret void\n"
"}\n"
"define void @a3() {\n"
"entry:\n"
" call void @a1()\n"
" ret void\n"
"}\n"
"define void @b1() {\n"
"entry:\n"
" call void @b2()\n"
" call void @d3()\n"
" ret void\n"
"}\n"
"define void @b2() {\n"
"entry:\n"
" call void @b3()\n"
" ret void\n"
"}\n"
"define void @b3() {\n"
"entry:\n"
" call void @b1()\n"
" ret void\n"
"}\n"
"define void @c1() {\n"
"entry:\n"
" call void @c2()\n"
" call void @d2()\n"
" ret void\n"
"}\n"
"define void @c2() {\n"
"entry:\n"
" call void @c3()\n"
" ret void\n"
"}\n"
"define void @c3() {\n"
"entry:\n"
" call void @c1()\n"
" ret void\n"
"}\n"
"define void @d1() {\n"
"entry:\n"
" call void @d2()\n"
" ret void\n"
"}\n"
"define void @d2() {\n"
"entry:\n"
" call void @d3()\n"
" ret void\n"
"}\n"
"define void @d3() {\n"
"entry:\n"
" call void @d1()\n"
" ret void\n"
"}\n";
TEST(LazyCallGraphTest, BasicGraphFormation) {
std::unique_ptr<Module> M = parseAssembly(DiamondOfTriangles);
LazyCallGraph CG(*M);
// The order of the entry nodes should be stable w.r.t. the source order of
// the IR, and everything in our module is an entry node, so just directly
// build variables for each node.
auto I = CG.begin();
LazyCallGraph::Node &A1 = *I++;
EXPECT_EQ("a1", A1.getFunction().getName());
LazyCallGraph::Node &A2 = *I++;
EXPECT_EQ("a2", A2.getFunction().getName());
LazyCallGraph::Node &A3 = *I++;
EXPECT_EQ("a3", A3.getFunction().getName());
LazyCallGraph::Node &B1 = *I++;
EXPECT_EQ("b1", B1.getFunction().getName());
LazyCallGraph::Node &B2 = *I++;
EXPECT_EQ("b2", B2.getFunction().getName());
LazyCallGraph::Node &B3 = *I++;
EXPECT_EQ("b3", B3.getFunction().getName());
LazyCallGraph::Node &C1 = *I++;
EXPECT_EQ("c1", C1.getFunction().getName());
LazyCallGraph::Node &C2 = *I++;
EXPECT_EQ("c2", C2.getFunction().getName());
LazyCallGraph::Node &C3 = *I++;
EXPECT_EQ("c3", C3.getFunction().getName());
LazyCallGraph::Node &D1 = *I++;
EXPECT_EQ("d1", D1.getFunction().getName());
LazyCallGraph::Node &D2 = *I++;
EXPECT_EQ("d2", D2.getFunction().getName());
LazyCallGraph::Node &D3 = *I++;
EXPECT_EQ("d3", D3.getFunction().getName());
EXPECT_EQ(CG.end(), I);
// Build vectors and sort them for the rest of the assertions to make them
// independent of order.
std::vector<std::string> Nodes;
for (LazyCallGraph::Node &N : A1)
Nodes.push_back(N.getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ("a2", Nodes[0]);
EXPECT_EQ("b2", Nodes[1]);
EXPECT_EQ("c3", Nodes[2]);
Nodes.clear();
EXPECT_EQ(A2.end(), std::next(A2.begin()));
EXPECT_EQ("a3", A2.begin()->getFunction().getName());
EXPECT_EQ(A3.end(), std::next(A3.begin()));
EXPECT_EQ("a1", A3.begin()->getFunction().getName());
for (LazyCallGraph::Node &N : B1)
Nodes.push_back(N.getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ("b2", Nodes[0]);
EXPECT_EQ("d3", Nodes[1]);
Nodes.clear();
EXPECT_EQ(B2.end(), std::next(B2.begin()));
EXPECT_EQ("b3", B2.begin()->getFunction().getName());
EXPECT_EQ(B3.end(), std::next(B3.begin()));
EXPECT_EQ("b1", B3.begin()->getFunction().getName());
for (LazyCallGraph::Node &N : C1)
Nodes.push_back(N.getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ("c2", Nodes[0]);
EXPECT_EQ("d2", Nodes[1]);
Nodes.clear();
EXPECT_EQ(C2.end(), std::next(C2.begin()));
EXPECT_EQ("c3", C2.begin()->getFunction().getName());
EXPECT_EQ(C3.end(), std::next(C3.begin()));
EXPECT_EQ("c1", C3.begin()->getFunction().getName());
EXPECT_EQ(D1.end(), std::next(D1.begin()));
EXPECT_EQ("d2", D1.begin()->getFunction().getName());
EXPECT_EQ(D2.end(), std::next(D2.begin()));
EXPECT_EQ("d3", D2.begin()->getFunction().getName());
EXPECT_EQ(D3.end(), std::next(D3.begin()));
EXPECT_EQ("d1", D3.begin()->getFunction().getName());
// Now lets look at the SCCs.
auto SCCI = CG.postorder_scc_begin();
LazyCallGraph::SCC &D = *SCCI++;
for (LazyCallGraph::Node *N : D)
Nodes.push_back(N->getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ(3u, Nodes.size());
EXPECT_EQ("d1", Nodes[0]);
EXPECT_EQ("d2", Nodes[1]);
EXPECT_EQ("d3", Nodes[2]);
Nodes.clear();
LazyCallGraph::SCC &C = *SCCI++;
for (LazyCallGraph::Node *N : C)
Nodes.push_back(N->getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ(3u, Nodes.size());
EXPECT_EQ("c1", Nodes[0]);
EXPECT_EQ("c2", Nodes[1]);
EXPECT_EQ("c3", Nodes[2]);
Nodes.clear();
LazyCallGraph::SCC &B = *SCCI++;
for (LazyCallGraph::Node *N : B)
Nodes.push_back(N->getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ(3u, Nodes.size());
EXPECT_EQ("b1", Nodes[0]);
EXPECT_EQ("b2", Nodes[1]);
EXPECT_EQ("b3", Nodes[2]);
Nodes.clear();
LazyCallGraph::SCC &A = *SCCI++;
for (LazyCallGraph::Node *N : A)
Nodes.push_back(N->getFunction().getName());
std::sort(Nodes.begin(), Nodes.end());
EXPECT_EQ(3u, Nodes.size());
EXPECT_EQ("a1", Nodes[0]);
EXPECT_EQ("a2", Nodes[1]);
EXPECT_EQ("a3", Nodes[2]);
Nodes.clear();
EXPECT_EQ(CG.postorder_scc_end(), SCCI);
}
static Function &lookupFunction(Module &M, StringRef Name) {
for (Function &F : M)
if (F.getName() == Name)
return F;
report_fatal_error("Couldn't find function!");
}
TEST(LazyCallGraphTest, MultiArmSCC) {
// Two interlocking cycles. The really useful thing about this SCC is that it
// will require Tarjan's DFS to backtrack and finish processing all of the
// children of each node in the SCC.
std::unique_ptr<Module> M = parseAssembly(
"define void @a() {\n"
"entry:\n"
" call void @b()\n"
" call void @d()\n"
" ret void\n"
"}\n"
"define void @b() {\n"
"entry:\n"
" call void @c()\n"
" ret void\n"
"}\n"
"define void @c() {\n"
"entry:\n"
" call void @a()\n"
" ret void\n"
"}\n"
"define void @d() {\n"
"entry:\n"
" call void @e()\n"
" ret void\n"
"}\n"
"define void @e() {\n"
"entry:\n"
" call void @a()\n"
" ret void\n"
"}\n");
LazyCallGraph CG(*M);
// Force the graph to be fully expanded.
auto SCCI = CG.postorder_scc_begin();
LazyCallGraph::SCC &SCC = *SCCI++;
EXPECT_EQ(CG.postorder_scc_end(), SCCI);
LazyCallGraph::Node &A = *CG.lookup(lookupFunction(*M, "a"));
LazyCallGraph::Node &B = *CG.lookup(lookupFunction(*M, "b"));
LazyCallGraph::Node &C = *CG.lookup(lookupFunction(*M, "c"));
LazyCallGraph::Node &D = *CG.lookup(lookupFunction(*M, "d"));
LazyCallGraph::Node &E = *CG.lookup(lookupFunction(*M, "e"));
EXPECT_EQ(&SCC, CG.lookupSCC(A));
EXPECT_EQ(&SCC, CG.lookupSCC(B));
EXPECT_EQ(&SCC, CG.lookupSCC(C));
EXPECT_EQ(&SCC, CG.lookupSCC(D));
EXPECT_EQ(&SCC, CG.lookupSCC(E));
}
TEST(LazyCallGraphTest, InterSCCEdgeRemoval) {
std::unique_ptr<Module> M = parseAssembly(
"define void @a() {\n"
"entry:\n"
" call void @b()\n"
" ret void\n"
"}\n"
"define void @b() {\n"
"entry:\n"
" ret void\n"
"}\n");
LazyCallGraph CG(*M);
// Force the graph to be fully expanded.
for (LazyCallGraph::SCC &C : CG.postorder_sccs())
(void)C;
LazyCallGraph::Node &A = *CG.lookup(lookupFunction(*M, "a"));
LazyCallGraph::Node &B = *CG.lookup(lookupFunction(*M, "b"));
LazyCallGraph::SCC &AC = *CG.lookupSCC(A);
LazyCallGraph::SCC &BC = *CG.lookupSCC(B);
EXPECT_EQ("b", A.begin()->getFunction().getName());
EXPECT_EQ(B.end(), B.begin());
EXPECT_EQ(&AC, &*BC.parent_begin());
AC.removeInterSCCEdge(A, B);
EXPECT_EQ(A.end(), A.begin());
EXPECT_EQ(B.end(), B.begin());
EXPECT_EQ(BC.parent_end(), BC.parent_begin());
}
TEST(LazyCallGraphTest, IntraSCCEdgeRemoval) {
// A nice fully connected (including self-edges) SCC.
std::unique_ptr<Module> M1 = parseAssembly(
"define void @a() {\n"
"entry:\n"
" call void @a()\n"
" call void @b()\n"
" call void @c()\n"
" ret void\n"
"}\n"
"define void @b() {\n"
"entry:\n"
" call void @a()\n"
" call void @b()\n"
" call void @c()\n"
" ret void\n"
"}\n"
"define void @c() {\n"
"entry:\n"
" call void @a()\n"
" call void @b()\n"
" call void @c()\n"
" ret void\n"
"}\n");
LazyCallGraph CG1(*M1);
// Force the graph to be fully expanded.
auto SCCI = CG1.postorder_scc_begin();
LazyCallGraph::SCC &SCC = *SCCI++;
EXPECT_EQ(CG1.postorder_scc_end(), SCCI);
LazyCallGraph::Node &A = *CG1.lookup(lookupFunction(*M1, "a"));
LazyCallGraph::Node &B = *CG1.lookup(lookupFunction(*M1, "b"));
LazyCallGraph::Node &C = *CG1.lookup(lookupFunction(*M1, "c"));
EXPECT_EQ(&SCC, CG1.lookupSCC(A));
EXPECT_EQ(&SCC, CG1.lookupSCC(B));
EXPECT_EQ(&SCC, CG1.lookupSCC(C));
// Remove the edge from b -> a, which should leave the 3 functions still in
// a single connected component because of a -> b -> c -> a.
SCC.removeIntraSCCEdge(B, A);
EXPECT_EQ(&SCC, CG1.lookupSCC(A));
EXPECT_EQ(&SCC, CG1.lookupSCC(B));
EXPECT_EQ(&SCC, CG1.lookupSCC(C));
// Remove the edge from c -> a, which should leave 'a' in the original SCC
// and form a new SCC for 'b' and 'c'.
SCC.removeIntraSCCEdge(C, A);
EXPECT_EQ(&SCC, CG1.lookupSCC(A));
EXPECT_EQ(1, std::distance(SCC.begin(), SCC.end()));
LazyCallGraph::SCC *SCC2 = CG1.lookupSCC(B);
EXPECT_EQ(SCC2, CG1.lookupSCC(C));
}
}
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