1 //===- DDGTest.cpp - DDGAnalysis unit tests -------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "llvm/Analysis/DDG.h"
10 #include "llvm/Analysis/AliasAnalysis.h"
11 #include "llvm/Analysis/AssumptionCache.h"
12 #include "llvm/Analysis/BasicAliasAnalysis.h"
13 #include "llvm/Analysis/LoopInfo.h"
14 #include "llvm/Analysis/ScalarEvolution.h"
15 #include "llvm/Analysis/TargetLibraryInfo.h"
16 #include "llvm/AsmParser/Parser.h"
17 #include "llvm/IR/Dominators.h"
18 #include "llvm/Support/SourceMgr.h"
19 #include "gtest/gtest.h"
20
21 using namespace llvm;
22
23 /// Build the DDG analysis for a loop and run the given test \p Test.
runTest(Module & M,StringRef FuncName,function_ref<void (Function & F,LoopInfo & LI,DependenceInfo & DI,ScalarEvolution & SE)> Test)24 static void runTest(Module &M, StringRef FuncName,
25 function_ref<void(Function &F, LoopInfo &LI,
26 DependenceInfo &DI, ScalarEvolution &SE)>
27 Test) {
28 auto *F = M.getFunction(FuncName);
29 ASSERT_NE(F, nullptr) << "Could not find " << FuncName;
30
31 TargetLibraryInfoImpl TLII;
32 TargetLibraryInfo TLI(TLII);
33 AssumptionCache AC(*F);
34 DominatorTree DT(*F);
35 LoopInfo LI(DT);
36 ScalarEvolution SE(*F, TLI, AC, DT, LI);
37 AAResults AA(TLI);
38 DependenceInfo DI(F, &AA, &SE, &LI);
39 Test(*F, LI, DI, SE);
40 }
41
makeLLVMModule(LLVMContext & Context,const char * ModuleStr)42 static std::unique_ptr<Module> makeLLVMModule(LLVMContext &Context,
43 const char *ModuleStr) {
44 SMDiagnostic Err;
45 return parseAssemblyString(ModuleStr, Err, Context);
46 }
47
TEST(DDGTest,getDependencies)48 TEST(DDGTest, getDependencies) {
49 const char *ModuleStr =
50 "target datalayout = \"e-m:e-i64:64-n32:64\"\n"
51 "target triple = \"powerpc64le-unknown-linux-gnu\"\n"
52 "\n"
53 "define dso_local void @foo(i32 signext %n, i32* noalias %A, i32* "
54 "noalias %B) {\n"
55 "entry:\n"
56 " %cmp1 = icmp sgt i32 %n, 0\n"
57 " br i1 %cmp1, label %for.body.preheader, label %for.end\n"
58 "\n"
59 "for.body.preheader:\n"
60 " %wide.trip.count = zext i32 %n to i64\n"
61 " br label %for.body\n"
62 " \n"
63 " for.body:\n"
64 " %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ "
65 "%indvars.iv.next, %for.body ]\n"
66 " %arrayidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv\n"
67 " %0 = trunc i64 %indvars.iv to i32\n"
68 " store i32 %0, i32* %arrayidx, align 4\n"
69 " %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1\n"
70 " %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 "
71 "%indvars.iv.next\n"
72 " %1 = load i32, i32* %arrayidx2, align 4\n"
73 " %add3 = add nsw i32 %1, 1\n"
74 " %arrayidx5 = getelementptr inbounds i32, i32* %B, i64 %indvars.iv\n"
75 " store i32 %add3, i32* %arrayidx5, align 4\n"
76 " %exitcond = icmp ne i64 %indvars.iv.next, %wide.trip.count\n"
77 " br i1 %exitcond, label %for.body, label %for.end.loopexit\n"
78 "\n"
79 "for.end.loopexit:\n"
80 " br label %for.end\n"
81 "\n"
82 "for.end:\n"
83 " ret void\n"
84 "}\n";
85
86 LLVMContext Context;
87 std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
88
89 runTest(
90 *M, "foo",
91 [&](Function &F, LoopInfo &LI, DependenceInfo &DI, ScalarEvolution &SE) {
92 Loop *L = *LI.begin();
93 assert(L && "expected the loop to be identified.");
94
95 DataDependenceGraph DDG(*L, LI, DI);
96
97 // Collect all the nodes that have an outgoing memory edge
98 // while collecting all memory edges as well. There should
99 // only be one node with an outgoing memory edge and there
100 // should only be one memory edge in the entire graph.
101 std::vector<DDGNode *> DependenceSourceNodes;
102 std::vector<DDGEdge *> MemoryEdges;
103 for (DDGNode *N : DDG) {
104 for (DDGEdge *E : *N) {
105 bool SourceAdded = false;
106 if (E->isMemoryDependence()) {
107 MemoryEdges.push_back(E);
108 if (!SourceAdded) {
109 DependenceSourceNodes.push_back(N);
110 SourceAdded = true;
111 }
112 }
113 }
114 }
115
116 EXPECT_EQ(DependenceSourceNodes.size(), 1ull);
117 EXPECT_EQ(MemoryEdges.size(), 1ull);
118
119 DataDependenceGraph::DependenceList DL;
120 DDG.getDependencies(*DependenceSourceNodes.back(),
121 MemoryEdges.back()->getTargetNode(), DL);
122
123 EXPECT_EQ(DL.size(), 1ull);
124 EXPECT_TRUE(DL.back()->isAnti());
125 EXPECT_EQ(DL.back()->getLevels(), 1u);
126 EXPECT_NE(DL.back()->getDistance(1), nullptr);
127 EXPECT_EQ(DL.back()->getDistance(1),
128 SE.getOne(DL.back()->getDistance(1)->getType()));
129 });
130 }
131
132 /// Test to make sure that when pi-blocks are formed, multiple edges of the same
133 /// kind and direction are collapsed into a single edge.
134 /// In the test below, %loadASubI belongs to an outside node, which has input
135 /// dependency with multiple load instructions in the pi-block containing
136 /// %loadBSubI. We expect a single memory dependence edge from the outside node
137 /// to this pi-block. The pi-block also contains %add and %add7 both of which
138 /// feed a phi in an outside node. We expect a single def-use edge from the
139 /// pi-block to the node containing that phi.
TEST(DDGTest,avoidDuplicateEdgesToFromPiBlocks)140 TEST(DDGTest, avoidDuplicateEdgesToFromPiBlocks) {
141 const char *ModuleStr =
142 "target datalayout = \"e-m:e-i64:64-n32:64-v256:256:256-v512:512:512\"\n"
143 "\n"
144 "define void @foo(float* noalias %A, float* noalias %B, float* noalias "
145 "%C, float* noalias %D, i32 signext %n) {\n"
146 "entry:\n"
147 " %cmp1 = icmp sgt i32 %n, 0\n"
148 " br i1 %cmp1, label %for.body.preheader, label %for.end\n"
149 "\n"
150 "for.body.preheader: ; preds = %entry\n"
151 " %wide.trip.count = zext i32 %n to i64\n"
152 " br label %for.body\n"
153 "\n"
154 "for.body: ; preds = "
155 "%for.body.preheader, %if.end\n"
156 " %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ %indvars.iv.next, "
157 "%if.end ]\n"
158 " %arrayidx = getelementptr inbounds float, float* %A, i64 %indvars.iv\n"
159 " %loadASubI = load float, float* %arrayidx, align 4\n"
160 " %arrayidx2 = getelementptr inbounds float, float* %B, i64 "
161 "%indvars.iv\n"
162 " %loadBSubI = load float, float* %arrayidx2, align 4\n"
163 " %add = fadd fast float %loadASubI, %loadBSubI\n"
164 " %arrayidx4 = getelementptr inbounds float, float* %A, i64 "
165 "%indvars.iv\n"
166 " store float %add, float* %arrayidx4, align 4\n"
167 " %arrayidx6 = getelementptr inbounds float, float* %A, i64 "
168 "%indvars.iv\n"
169 " %0 = load float, float* %arrayidx6, align 4\n"
170 " %add7 = fadd fast float %0, 1.000000e+00\n"
171 " %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1\n"
172 " %arrayidx10 = getelementptr inbounds float, float* %B, i64 "
173 "%indvars.iv.next\n"
174 " store float %add7, float* %arrayidx10, align 4\n"
175 " %arrayidx12 = getelementptr inbounds float, float* %A, i64 "
176 "%indvars.iv\n"
177 " %1 = load float, float* %arrayidx12, align 4\n"
178 " %cmp13 = fcmp fast ogt float %1, 1.000000e+02\n"
179 " br i1 %cmp13, label %if.then, label %if.else\n"
180 "\n"
181 "if.then: ; preds = %for.body\n"
182 " br label %if.end\n"
183 "\n"
184 "if.else: ; preds = %for.body\n"
185 " br label %if.end\n"
186 "\n"
187 "if.end: ; preds = %if.else, "
188 "%if.then\n"
189 " %ff.0 = phi float [ %add, %if.then ], [ %add7, %if.else ]\n"
190 " store float %ff.0, float* %C, align 4\n"
191 " %exitcond = icmp ne i64 %indvars.iv.next, %wide.trip.count\n"
192 " br i1 %exitcond, label %for.body, label %for.end.loopexit\n"
193 "\n"
194 "for.end.loopexit: ; preds = %if.end\n"
195 " br label %for.end\n"
196 "\n"
197 "for.end: ; preds = "
198 "%for.end.loopexit, %entry\n"
199 " ret void\n"
200 "}\n";
201
202 LLVMContext Context;
203 std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
204
205 runTest(
206 *M, "foo",
207 [&](Function &F, LoopInfo &LI, DependenceInfo &DI, ScalarEvolution &SE) {
208 Loop *L = *LI.begin();
209 assert(L && "expected the loop to be identified.");
210
211 DataDependenceGraph DDG(*L, LI, DI);
212
213 const DDGNode *LoadASubI = nullptr;
214 for (DDGNode *N : DDG) {
215 if (!isa<SimpleDDGNode>(N))
216 continue;
217 SmallVector<Instruction *, 8> IList;
218 N->collectInstructions([](const Instruction *I) { return true; },
219 IList);
220 if (llvm::any_of(IList, [](Instruction *I) {
221 return I->getName() == "loadASubI";
222 })) {
223 LoadASubI = N;
224 break;
225 }
226 }
227 assert(LoadASubI && "Did not find load of A[i]");
228
229 const PiBlockDDGNode *PiBlockWithBSubI = nullptr;
230 for (DDGNode *N : DDG) {
231 if (!isa<PiBlockDDGNode>(N))
232 continue;
233 for (DDGNode *M : cast<PiBlockDDGNode>(N)->getNodes()) {
234 SmallVector<Instruction *, 8> IList;
235 M->collectInstructions([](const Instruction *I) { return true; },
236 IList);
237 if (llvm::any_of(IList, [](Instruction *I) {
238 return I->getName() == "loadBSubI";
239 })) {
240 PiBlockWithBSubI = static_cast<PiBlockDDGNode *>(N);
241 break;
242 }
243 }
244 if (PiBlockWithBSubI)
245 break;
246 }
247 assert(PiBlockWithBSubI &&
248 "Did not find pi-block containing load of B[i]");
249
250 const DDGNode *FFPhi = nullptr;
251 for (DDGNode *N : DDG) {
252 if (!isa<SimpleDDGNode>(N))
253 continue;
254 SmallVector<Instruction *, 8> IList;
255 N->collectInstructions([](const Instruction *I) { return true; },
256 IList);
257 if (llvm::any_of(IList, [](Instruction *I) {
258 return I->getName() == "ff.0";
259 })) {
260 FFPhi = N;
261 break;
262 }
263 }
264 assert(FFPhi && "Did not find ff.0 phi instruction");
265
266 // Expect a single memory edge from '%0 = A[i]' to the pi-block. This
267 // means the duplicate incoming memory edges are removed during pi-block
268 // formation.
269 SmallVector<DDGEdge *, 4> EL;
270 LoadASubI->findEdgesTo(*PiBlockWithBSubI, EL);
271 unsigned NumMemoryEdges = llvm::count_if(
272 EL, [](DDGEdge *Edge) { return Edge->isMemoryDependence(); });
273 EXPECT_EQ(NumMemoryEdges, 1ull);
274
275 /// Expect a single def-use edge from the pi-block to '%ff.0 = phi...`.
276 /// This means the duplicate outgoing def-use edges are removed during
277 /// pi-block formation.
278 EL.clear();
279 PiBlockWithBSubI->findEdgesTo(*FFPhi, EL);
280 NumMemoryEdges =
281 llvm::count_if(EL, [](DDGEdge *Edge) { return Edge->isDefUse(); });
282 EXPECT_EQ(NumMemoryEdges, 1ull);
283 });
284 }
285