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llvm-6502/unittests/Analysis/LazyCallGraphTest.cpp
Chandler Carruth e42618b4bc [LCG] Add the first round of mutation support to the lazy call graph. 
This implements the core functionality necessary to remove an edge from
the call graph and correctly update both the basic graph and the SCC
structure. As part of that it has to run a tiny (in number of nodes)
Tarjan-style DFS walk of an SCC being mutated to compute newly formed
SCCs, etc.

This is *very rough* and a WIP. I have a bunch of FIXMEs for code
cleanup that will reduce the boilerplate in this change substantially.
I also have a bunch of simplifications to various parts of both
algorithms that I want to make, but first I'd like to have a more
holistic picture. Ideally, I'd also like more testing. I'll probably add
quite a few more unit tests as I go here to cover the various different
aspects and corner cases of removing edges from the graph.

Still, this is, so far, successfully updating the SCC graph in-place
without disrupting the identity established for the existing SCCs even
when we do challenging things like delete the critical edge that made an
SCC cycle at all and have to reform things as a tree of smaller SCCs.
Getting this to work is really critical for the new pass manager as it
is going to associate significant state with the SCC instance and needs
it to be stable. That is also the motivation behind the return of the
newly formed SCCs. Eventually, I'll wire this all the way up to the
public API so that the pass manager can use it to correctly re-enqueue
newly formed SCCs into a fresh postorder traversal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206968 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 11:03:03 +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("d1", Nodes[0]);
EXPECT_EQ("d2", Nodes[1]);
EXPECT_EQ("d3", Nodes[2]);
EXPECT_EQ(3u, Nodes.size());
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("c1", Nodes[0]);
EXPECT_EQ("c2", Nodes[1]);
EXPECT_EQ("c3", Nodes[2]);
EXPECT_EQ(3u, Nodes.size());
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("b1", Nodes[0]);
EXPECT_EQ("b2", Nodes[1]);
EXPECT_EQ("b3", Nodes[2]);
EXPECT_EQ(3u, Nodes.size());
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("a1", Nodes[0]);
EXPECT_EQ("a2", Nodes[1]);
EXPECT_EQ("a3", Nodes[2]);
EXPECT_EQ(3u, Nodes.size());
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->getFunction()));
EXPECT_EQ(SCC, CG.lookupSCC(B->getFunction()));
EXPECT_EQ(SCC, CG.lookupSCC(C->getFunction()));
EXPECT_EQ(SCC, CG.lookupSCC(D->getFunction()));
EXPECT_EQ(SCC, CG.lookupSCC(E->getFunction()));
}
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(lookupFunction(*M, "a"));
LazyCallGraph::SCC *BC = CG.lookupSCC(lookupFunction(*M, "b"));
EXPECT_EQ("b", A->begin()->getFunction().getName());
EXPECT_EQ(B->end(), B->begin());
EXPECT_EQ(AC, *BC->parent_begin());
CG.removeEdge(*A, lookupFunction(*M, "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->getFunction()));
EXPECT_EQ(SCC, CG1.lookupSCC(B->getFunction()));
EXPECT_EQ(SCC, CG1.lookupSCC(C->getFunction()));
// Remove the edge from b -> a, which should leave the 3 functions still in
// a single connected component because of a -> b -> c -> a.
CG1.removeEdge(*B, A->getFunction());
EXPECT_EQ(SCC, CG1.lookupSCC(A->getFunction()));
EXPECT_EQ(SCC, CG1.lookupSCC(B->getFunction()));
EXPECT_EQ(SCC, CG1.lookupSCC(C->getFunction()));
// Remove the edge from c -> a, which should leave 'a' in the original SCC
// and form a new SCC for 'b' and 'c'.
CG1.removeEdge(*C, A->getFunction());
EXPECT_EQ(SCC, CG1.lookupSCC(A->getFunction()));
EXPECT_EQ(1, std::distance(SCC->begin(), SCC->end()));
LazyCallGraph::SCC *SCC2 = CG1.lookupSCC(B->getFunction());
EXPECT_EQ(SCC2, CG1.lookupSCC(C->getFunction()));
}
}
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