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/IR/Module.h"
19 #include "llvm/Support/SourceMgr.h"
20 #include "gtest/gtest.h"
21
22 using namespace llvm;
23
24 /// 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)25 static void runTest(Module &M, StringRef FuncName,
26 function_ref<void(Function &F, LoopInfo &LI,
27 DependenceInfo &DI, ScalarEvolution &SE)>
28 Test) {
29 auto *F = M.getFunction(FuncName);
30 ASSERT_NE(F, nullptr) << "Could not find " << FuncName;
31
32 TargetLibraryInfoImpl TLII;
33 TargetLibraryInfo TLI(TLII);
34 AssumptionCache AC(*F);
35 DominatorTree DT(*F);
36 LoopInfo LI(DT);
37 ScalarEvolution SE(*F, TLI, AC, DT, LI);
38 AAResults AA(TLI);
39 DependenceInfo DI(F, &AA, &SE, &LI);
40 Test(*F, LI, DI, SE);
41 }
42
makeLLVMModule(LLVMContext & Context,const char * ModuleStr)43 static std::unique_ptr<Module> makeLLVMModule(LLVMContext &Context,
44 const char *ModuleStr) {
45 SMDiagnostic Err;
46 return parseAssemblyString(ModuleStr, Err, Context);
47 }
48
TEST(DDGTest,getDependencies)49 TEST(DDGTest, getDependencies) {
50 const char *ModuleStr =
51 "target datalayout = \"e-m:e-i64:64-n32:64\"\n"
52 "target triple = \"powerpc64le-unknown-linux-gnu\"\n"
53 "\n"
54 "define dso_local void @foo(i32 signext %n, i32* noalias %A, i32* "
55 "noalias %B) {\n"
56 "entry:\n"
57 " %cmp1 = icmp sgt i32 %n, 0\n"
58 " br i1 %cmp1, label %for.body.preheader, label %for.end\n"
59 "\n"
60 "for.body.preheader:\n"
61 " %wide.trip.count = zext i32 %n to i64\n"
62 " br label %for.body\n"
63 " \n"
64 " for.body:\n"
65 " %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ "
66 "%indvars.iv.next, %for.body ]\n"
67 " %arrayidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv\n"
68 " %0 = trunc i64 %indvars.iv to i32\n"
69 " store i32 %0, i32* %arrayidx, align 4\n"
70 " %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1\n"
71 " %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 "
72 "%indvars.iv.next\n"
73 " %1 = load i32, i32* %arrayidx2, align 4\n"
74 " %add3 = add nsw i32 %1, 1\n"
75 " %arrayidx5 = getelementptr inbounds i32, i32* %B, i64 %indvars.iv\n"
76 " store i32 %add3, i32* %arrayidx5, align 4\n"
77 " %exitcond = icmp ne i64 %indvars.iv.next, %wide.trip.count\n"
78 " br i1 %exitcond, label %for.body, label %for.end.loopexit\n"
79 "\n"
80 "for.end.loopexit:\n"
81 " br label %for.end\n"
82 "\n"
83 "for.end:\n"
84 " ret void\n"
85 "}\n";
86
87 LLVMContext Context;
88 std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
89
90 runTest(
91 *M, "foo",
92 [&](Function &F, LoopInfo &LI, DependenceInfo &DI, ScalarEvolution &SE) {
93 Loop *L = *LI.begin();
94 assert(L && "expected the loop to be identified.");
95
96 DataDependenceGraph DDG(*L, LI, DI);
97
98 // Collect all the nodes that have an outgoing memory edge
99 // while collecting all memory edges as well. There should
100 // only be one node with an outgoing memory edge and there
101 // should only be one memory edge in the entire graph.
102 std::vector<DDGNode *> DependenceSourceNodes;
103 std::vector<DDGEdge *> MemoryEdges;
104 for (DDGNode *N : DDG) {
105 for (DDGEdge *E : *N) {
106 bool SourceAdded = false;
107 if (E->isMemoryDependence()) {
108 MemoryEdges.push_back(E);
109 if (!SourceAdded) {
110 DependenceSourceNodes.push_back(N);
111 SourceAdded = true;
112 }
113 }
114 }
115 }
116
117 EXPECT_EQ(DependenceSourceNodes.size(), 1ull);
118 EXPECT_EQ(MemoryEdges.size(), 1ull);
119
120 DataDependenceGraph::DependenceList DL;
121 DDG.getDependencies(*DependenceSourceNodes.back(),
122 MemoryEdges.back()->getTargetNode(), DL);
123
124 EXPECT_EQ(DL.size(), 1ull);
125 EXPECT_TRUE(DL.back()->isAnti());
126 EXPECT_EQ(DL.back()->getLevels(), 1u);
127 EXPECT_NE(DL.back()->getDistance(1), nullptr);
128 EXPECT_EQ(DL.back()->getDistance(1),
129 SE.getOne(DL.back()->getDistance(1)->getType()));
130 });
131 }
132
133 /// Test to make sure that when pi-blocks are formed, multiple edges of the same
134 /// kind and direction are collapsed into a single edge.
135 /// In the test below, %loadASubI belongs to an outside node, which has input
136 /// dependency with multiple load instructions in the pi-block containing
137 /// %loadBSubI. We expect a single memory dependence edge from the outside node
138 /// to this pi-block. The pi-block also contains %add and %add7 both of which
139 /// feed a phi in an outside node. We expect a single def-use edge from the
140 /// pi-block to the node containing that phi.
TEST(DDGTest,avoidDuplicateEdgesToFromPiBlocks)141 TEST(DDGTest, avoidDuplicateEdgesToFromPiBlocks) {
142 const char *ModuleStr =
143 "target datalayout = \"e-m:e-i64:64-n32:64-v256:256:256-v512:512:512\"\n"
144 "\n"
145 "define void @foo(float* noalias %A, float* noalias %B, float* noalias "
146 "%C, float* noalias %D, i32 signext %n) {\n"
147 "entry:\n"
148 " %cmp1 = icmp sgt i32 %n, 0\n"
149 " br i1 %cmp1, label %for.body.preheader, label %for.end\n"
150 "\n"
151 "for.body.preheader: ; preds = %entry\n"
152 " %wide.trip.count = zext i32 %n to i64\n"
153 " br label %for.body\n"
154 "\n"
155 "for.body: ; preds = "
156 "%for.body.preheader, %if.end\n"
157 " %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ %indvars.iv.next, "
158 "%if.end ]\n"
159 " %arrayidx = getelementptr inbounds float, float* %A, i64 %indvars.iv\n"
160 " %loadASubI = load float, float* %arrayidx, align 4\n"
161 " %arrayidx2 = getelementptr inbounds float, float* %B, i64 "
162 "%indvars.iv\n"
163 " %loadBSubI = load float, float* %arrayidx2, align 4\n"
164 " %add = fadd fast float %loadASubI, %loadBSubI\n"
165 " %arrayidx4 = getelementptr inbounds float, float* %A, i64 "
166 "%indvars.iv\n"
167 " store float %add, float* %arrayidx4, align 4\n"
168 " %arrayidx6 = getelementptr inbounds float, float* %A, i64 "
169 "%indvars.iv\n"
170 " %0 = load float, float* %arrayidx6, align 4\n"
171 " %add7 = fadd fast float %0, 1.000000e+00\n"
172 " %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1\n"
173 " %arrayidx10 = getelementptr inbounds float, float* %B, i64 "
174 "%indvars.iv.next\n"
175 " store float %add7, float* %arrayidx10, align 4\n"
176 " %arrayidx12 = getelementptr inbounds float, float* %A, i64 "
177 "%indvars.iv\n"
178 " %1 = load float, float* %arrayidx12, align 4\n"
179 " %cmp13 = fcmp fast ogt float %1, 1.000000e+02\n"
180 " br i1 %cmp13, label %if.then, label %if.else\n"
181 "\n"
182 "if.then: ; preds = %for.body\n"
183 " br label %if.end\n"
184 "\n"
185 "if.else: ; preds = %for.body\n"
186 " br label %if.end\n"
187 "\n"
188 "if.end: ; preds = %if.else, "
189 "%if.then\n"
190 " %ff.0 = phi float [ %add, %if.then ], [ %add7, %if.else ]\n"
191 " store float %ff.0, float* %C, align 4\n"
192 " %exitcond = icmp ne i64 %indvars.iv.next, %wide.trip.count\n"
193 " br i1 %exitcond, label %for.body, label %for.end.loopexit\n"
194 "\n"
195 "for.end.loopexit: ; preds = %if.end\n"
196 " br label %for.end\n"
197 "\n"
198 "for.end: ; preds = "
199 "%for.end.loopexit, %entry\n"
200 " ret void\n"
201 "}\n";
202
203 LLVMContext Context;
204 std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
205
206 runTest(
207 *M, "foo",
208 [&](Function &F, LoopInfo &LI, DependenceInfo &DI, ScalarEvolution &SE) {
209 Loop *L = *LI.begin();
210 assert(L && "expected the loop to be identified.");
211
212 DataDependenceGraph DDG(*L, LI, DI);
213
214 const DDGNode *LoadASubI = nullptr;
215 for (DDGNode *N : DDG) {
216 if (!isa<SimpleDDGNode>(N))
217 continue;
218 SmallVector<Instruction *, 8> IList;
219 N->collectInstructions([](const Instruction *I) { return true; },
220 IList);
221 if (llvm::any_of(IList, [](Instruction *I) {
222 return I->getName() == "loadASubI";
223 })) {
224 LoadASubI = N;
225 break;
226 }
227 }
228 assert(LoadASubI && "Did not find load of A[i]");
229
230 const PiBlockDDGNode *PiBlockWithBSubI = nullptr;
231 for (DDGNode *N : DDG) {
232 if (!isa<PiBlockDDGNode>(N))
233 continue;
234 for (DDGNode *M : cast<PiBlockDDGNode>(N)->getNodes()) {
235 SmallVector<Instruction *, 8> IList;
236 M->collectInstructions([](const Instruction *I) { return true; },
237 IList);
238 if (llvm::any_of(IList, [](Instruction *I) {
239 return I->getName() == "loadBSubI";
240 })) {
241 PiBlockWithBSubI = static_cast<PiBlockDDGNode *>(N);
242 break;
243 }
244 }
245 if (PiBlockWithBSubI)
246 break;
247 }
248 assert(PiBlockWithBSubI &&
249 "Did not find pi-block containing load of B[i]");
250
251 const DDGNode *FFPhi = nullptr;
252 for (DDGNode *N : DDG) {
253 if (!isa<SimpleDDGNode>(N))
254 continue;
255 SmallVector<Instruction *, 8> IList;
256 N->collectInstructions([](const Instruction *I) { return true; },
257 IList);
258 if (llvm::any_of(IList, [](Instruction *I) {
259 return I->getName() == "ff.0";
260 })) {
261 FFPhi = N;
262 break;
263 }
264 }
265 assert(FFPhi && "Did not find ff.0 phi instruction");
266
267 // Expect a single memory edge from '%0 = A[i]' to the pi-block. This
268 // means the duplicate incoming memory edges are removed during pi-block
269 // formation.
270 SmallVector<DDGEdge *, 4> EL;
271 LoadASubI->findEdgesTo(*PiBlockWithBSubI, EL);
272 unsigned NumMemoryEdges = llvm::count_if(
273 EL, [](DDGEdge *Edge) { return Edge->isMemoryDependence(); });
274 EXPECT_EQ(NumMemoryEdges, 1ull);
275
276 /// Expect a single def-use edge from the pi-block to '%ff.0 = phi...`.
277 /// This means the duplicate outgoing def-use edges are removed during
278 /// pi-block formation.
279 EL.clear();
280 PiBlockWithBSubI->findEdgesTo(*FFPhi, EL);
281 NumMemoryEdges =
282 llvm::count_if(EL, [](DDGEdge *Edge) { return Edge->isDefUse(); });
283 EXPECT_EQ(NumMemoryEdges, 1ull);
284 });
285 }
286