llvm/unittests/Analysis/DDGTest.cpp

   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.
  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
  43 static std::unique_ptr<Module> makeLLVMModule(LLVMContext &Context,
  44                                               const char *ModuleStr) {
  45   SMDiagnostic Err;
  46   return parseAssemblyString(ModuleStr, Err, Context);
  47 }
  48
  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.
 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 }