llvm/unittests/Analysis/LoopNestTest.cpp

   1 //===- LoopNestTest.cpp - LoopNestAnalysis 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/AssumptionCache.h"
  10 #include "llvm/Analysis/LoopNestAnalysis.h"
  11 #include "llvm/Analysis/ScalarEvolution.h"
  12 #include "llvm/Analysis/TargetLibraryInfo.h"
  13 #include "llvm/AsmParser/Parser.h"
  14 #include "llvm/IR/Dominators.h"
  15 #include "llvm/Support/SourceMgr.h"
  16 #include "gtest/gtest.h"
  17
  18 using namespace llvm;
  19
  20 /// Build the loop nest analysis for a loop nest and run the given test \p Test.
  21 static void runTest(
  22     Module &M, StringRef FuncName,
  23     function_ref<void(Function &F, LoopInfo &LI, ScalarEvolution &SE)> Test) {
  24   auto *F = M.getFunction(FuncName);
  25   ASSERT_NE(F, nullptr) << "Could not find " << FuncName;
  26
  27   TargetLibraryInfoImpl TLII;
  28   TargetLibraryInfo TLI(TLII);
  29   AssumptionCache AC(*F);
  30   DominatorTree DT(*F);
  31   LoopInfo LI(DT);
  32   ScalarEvolution SE(*F, TLI, AC, DT, LI);
  33
  34   Test(*F, LI, SE);
  35 }
  36
  37 static std::unique_ptr<Module> makeLLVMModule(LLVMContext &Context,
  38                                               const char *ModuleStr) {
  39   SMDiagnostic Err;
  40   return parseAssemblyString(ModuleStr, Err, Context);
  41 }
  42
  43 static Instruction *getInstructionByName(Function &F, StringRef Name) {
  44   for (BasicBlock &BB : F)
  45     for (Instruction &I : BB)
  46       if (I.getName() == Name)
  47         return &I;
  48   llvm_unreachable("Expected to find instruction!");
  49 }
  50
  51 TEST(LoopNestTest, PerfectLoopNest) {
  52   const char *ModuleStr =
  53     "target datalayout = \"e-m:o-i64:64-f80:128-n8:16:32:64-S128\"\n"
  54     "define void @foo(i64 signext %nx, i64 signext %ny) {\n"
  55     "entry:\n"
  56     "  br label %for.outer\n"
  57     "for.outer:\n"
  58     "  %i = phi i64 [ 0, %entry ], [ %inc13, %for.outer.latch ]\n"
  59     "  %cmp21 = icmp slt i64 0, %ny\n"
  60     "  br i1 %cmp21, label %for.inner.preheader, label %for.outer.latch\n"
  61     "for.inner.preheader:\n"
  62     "  br label %for.inner\n"
  63     "for.inner:\n"
  64     "  %j = phi i64 [ 0, %for.inner.preheader ], [ %inc, %for.inner.latch ]\n"
  65     "  br label %for.inner.latch\n"
  66     "for.inner.latch:\n"
  67     "  %inc = add nsw i64 %j, 1\n"
  68     "  %cmp2 = icmp slt i64 %inc, %ny\n"
  69     "  br i1 %cmp2, label %for.inner, label %for.inner.exit\n"
  70     "for.inner.exit:\n"
  71     "  br label %for.outer.latch\n"
  72     "for.outer.latch:\n"
  73     "  %inc13 = add nsw i64 %i, 1\n"
  74     "  %cmp = icmp slt i64 %inc13, %nx\n"
  75     "  br i1 %cmp, label %for.outer, label %for.outer.exit\n"
  76     "for.outer.exit:\n"
  77     "  br label %for.end\n"
  78     "for.end:\n"
  79     "  ret void\n"
  80     "}\n";
  81
  82   LLVMContext Context;
  83   std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
  84
  85   runTest(*M, "foo", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
  86     Function::iterator FI = F.begin();
  87     // Skip the first basic block (entry), get to the outer loop header.
  88     BasicBlock *Header = &*(++FI);
  89     assert(Header->getName() == "for.outer");
  90     Loop *L = LI.getLoopFor(Header);
  91     EXPECT_NE(L, nullptr);
  92
  93     LoopNest LN(*L, SE);
  94     EXPECT_TRUE(LN.areAllLoopsSimplifyForm());
  95
  96     // Ensure that we can identify the outermost loop in the nest.
  97     const Loop &OL = LN.getOutermostLoop();
  98     EXPECT_EQ(OL.getName(), "for.outer");
  99
 100     // Ensure that we can identify the innermost loop in the nest.
 101     const Loop *IL = LN.getInnermostLoop();
 102     EXPECT_NE(IL, nullptr);
 103     EXPECT_EQ(IL->getName(), "for.inner");
 104
 105     // Ensure the loop nest is recognized as having 2 loops.
 106     const ArrayRef<Loop*> Loops = LN.getLoops();
 107     EXPECT_EQ(Loops.size(), 2ull);
 108
 109     // Ensure that we can obtain loops by depth.
 110     LoopVectorTy LoopsAtDepth1 = LN.getLoopsAtDepth(1);
 111     EXPECT_EQ(LoopsAtDepth1.size(), 1u);
 112     EXPECT_EQ(LoopsAtDepth1[0], &OL);
 113     LoopVectorTy LoopsAtDepth2 = LN.getLoopsAtDepth(2);
 114     EXPECT_EQ(LoopsAtDepth2.size(), 1u);
 115     EXPECT_EQ(LoopsAtDepth2[0], IL);
 116
 117     // Ensure that we can obtain the loop index of a given loop, and get back
 118     // the loop with that index.
 119     EXPECT_EQ(LN.getLoop(LN.getLoopIndex(OL)), &OL);
 120     EXPECT_EQ(LN.getLoop(LN.getLoopIndex(*IL)), IL);
 121
 122     // Ensure the loop nest is recognized as perfect in its entirety.
 123     const SmallVector<LoopVectorTy, 4> &PLV = LN.getPerfectLoops(SE);
 124     EXPECT_EQ(PLV.size(), 1ull);
 125     EXPECT_EQ(PLV.front().size(), 2ull);
 126
 127     // Ensure the nest depth and perfect nest depth are computed correctly.
 128     EXPECT_EQ(LN.getNestDepth(), 2u);
 129     EXPECT_EQ(LN.getMaxPerfectDepth(), 2u);
 130
 131     EXPECT_TRUE(LN.getInterveningInstructions(OL, *IL, SE).empty());
 132   });
 133 }
 134
 135 TEST(LoopNestTest, ImperfectLoopNest) {
 136   const char *ModuleStr =
 137       "target datalayout = \"e-m:o-i64:64-f80:128-n8:16:32:64-S128\"\n"
 138       "define void @foo(i32 signext %nx, i32 signext %ny, i32 signext %nk) {\n"
 139       "entry:\n"
 140       "  br label %loop.i\n"
 141       "loop.i:\n"
 142       "  %i = phi i32 [ 0, %entry ], [ %inci, %for.inci ]\n"
 143       "  %cmp21 = icmp slt i32 0, %ny\n"
 144       "  br i1 %cmp21, label %loop.j.preheader, label %for.inci\n"
 145       "loop.j.preheader:\n"
 146       "  br label %loop.j\n"
 147       "loop.j:\n"
 148       "  %j = phi i32 [ %incj, %for.incj ], [ 0, %loop.j.preheader ]\n"
 149       "  %cmp22 = icmp slt i32 0, %nk\n"
 150       "  br i1 %cmp22, label %loop.k.preheader, label %for.incj\n"
 151       "loop.k.preheader:\n"
 152       "  call void @bar()\n"
 153       "  br label %loop.k\n"
 154       "loop.k:\n"
 155       "  %k = phi i32 [ %inck, %for.inck ], [ 0, %loop.k.preheader ]\n"
 156       "  br label %for.inck\n"
 157       "for.inck:\n"
 158       "  %inck = add nsw i32 %k, 1\n"
 159       "  %cmp5 = icmp slt i32 %inck, %nk\n"
 160       "  br i1 %cmp5, label %loop.k, label %for.incj.loopexit\n"
 161       "for.incj.loopexit:\n"
 162       "  br label %for.incj\n"
 163       "for.incj:\n"
 164       "  %incj = add nsw i32 %j, 1\n"
 165       "  %cmp2 = icmp slt i32 %incj, %ny\n"
 166       "  br i1 %cmp2, label %loop.j, label %for.inci.loopexit\n"
 167       "for.inci.loopexit:\n"
 168       "  br label %for.inci\n"
 169       "for.inci:\n"
 170       "  %inci = add nsw i32 %i, 1\n"
 171       "  %cmp = icmp slt i32 %inci, %nx\n"
 172       "  br i1 %cmp, label %loop.i, label %loop.i.end\n"
 173       "loop.i.end:\n"
 174       "  ret void\n"
 175       "}\n"
 176       "declare void @bar()\n";
 177
 178   LLVMContext Context;
 179   std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
 180
 181   runTest(*M, "foo", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
 182     Function::iterator FI = F.begin();
 183     // Skip the first basic block (entry), get to the outermost loop header.
 184     BasicBlock *Header = &*(++FI);
 185     assert(Header->getName() == "loop.i");
 186     Loop *L = LI.getLoopFor(Header);
 187     EXPECT_NE(L, nullptr);
 188
 189     LoopNest LN(*L, SE);
 190     EXPECT_TRUE(LN.areAllLoopsSimplifyForm());
 191
 192     dbgs() << "LN: " << LN << "\n";
 193
 194     // Ensure that we can identify the outermost loop in the nest.
 195     const Loop &OL = LN.getOutermostLoop();
 196     EXPECT_EQ(OL.getName(), "loop.i");
 197
 198     // Ensure that we can identify the innermost loop in the nest.
 199     const Loop *IL = LN.getInnermostLoop();
 200     EXPECT_NE(IL, nullptr);
 201     EXPECT_EQ(IL->getName(), "loop.k");
 202
 203     // Ensure the loop nest is recognized as having 3 loops.
 204     const ArrayRef<Loop*> Loops = LN.getLoops();
 205     EXPECT_EQ(Loops.size(), 3ull);
 206
 207     // Ensure the loop nest is recognized as having 2 separate perfect loops groups.
 208     const SmallVector<LoopVectorTy, 4> &PLV = LN.getPerfectLoops(SE);
 209     EXPECT_EQ(PLV.size(), 2ull);
 210     EXPECT_EQ(PLV.front().size(), 2ull);
 211     EXPECT_EQ(PLV.back().size(), 1ull);
 212
 213     // Ensure the nest depth and perfect nest depth are computed correctly.
 214     EXPECT_EQ(LN.getNestDepth(), 3u);
 215     EXPECT_EQ(LN.getMaxPerfectDepth(), 2u);
 216
 217     EXPECT_TRUE(LN.getInterveningInstructions(OL, *IL, SE).empty());
 218   });
 219 }
 220
 221 TEST(LoopNestTest, InterveningInstrLoopNest) {
 222   const char *ModuleStr =
 223       "target datalayout = \"e-m:o-i64:64-f80:128-n8:16:32:64-S128\"\n"
 224       "define void @foo(i64 signext %nx, i64 signext %ny, i32* noalias %A, i32 "
 225       "%op0, i32 %op1){\n"
 226       "entry:\n"
 227       "  br label %for.outer\n"
 228       "for.outer:\n"
 229       "  %i = phi i64 [ 0, %entry ], [ %inc13, %for.outer.latch ]\n"
 230       "  %cmp21 = icmp slt i64 0, %ny\n"
 231       "  call void @outerheader()\n"
 232       "  br i1 %cmp21, label %for.inner.preheader, label %for.outer.latch\n"
 233       "for.inner.preheader:\n"
 234       "  %varr = getelementptr inbounds i32, i32* %A, i64 5\n"
 235       "  store i32 5, i32* %varr, align 4\n"
 236       "  call void @innerpreheader()\n"
 237       "  br label %for.inner\n"
 238       "for.inner:\n"
 239       "  %j = phi i64 [ 0, %for.inner.preheader ], [ %inc, %for.inner.latch ]\n"
 240       "  br label %for.inner.latch\n"
 241       "for.inner.latch:\n"
 242       "  %inc = add nsw i64 %j, 1\n"
 243       "  %cmp2 = icmp slt i64 %inc, %ny\n"
 244       "  br i1 %cmp2, label %for.inner, label %for.inner.exit\n"
 245       "for.inner.exit:\n"
 246       "  %varr1 = getelementptr inbounds i32, i32* %A, i64 5\n"
 247       "  call void @innerexit()\n"
 248       "  br label %for.outer.latch\n"
 249       "for.outer.latch:\n"
 250       "  %inc13 = add nsw i64 %i, 1\n"
 251       "  call void @outerlatch()\n"
 252       "  %cmp = icmp slt i64 %inc13, %nx\n"
 253       "  br i1 %cmp, label %for.outer, label %for.outer.exit\n"
 254       "for.outer.exit:\n"
 255       "  br label %for.end\n"
 256       "for.end:\n"
 257       "  ret void\n"
 258       "}\n"
 259       "declare void @innerpreheader()\n"
 260       "declare void @outerheader()\n"
 261       "declare void @outerlatch()\n"
 262       "declare void @innerexit()\n";
 263
 264   LLVMContext Context;
 265   std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
 266
 267   runTest(*M, "foo", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
 268     Function::iterator FI = F.begin();
 269     // Skip the first basic block (entry), get to the outer loop header.
 270     BasicBlock *Header = &*(++FI);
 271     assert(Header->getName() == "for.outer");
 272     Loop *L = LI.getLoopFor(Header);
 273     EXPECT_NE(L, nullptr);
 274
 275     LoopNest LN(*L, SE);
 276     EXPECT_TRUE(LN.areAllLoopsSimplifyForm());
 277
 278     // Ensure that we can identify the outermost loop in the nest.
 279     const Loop &OL = LN.getOutermostLoop();
 280     EXPECT_EQ(OL.getName(), "for.outer");
 281
 282     // Ensure that we can identify the innermost loop in the nest.
 283     const Loop *IL = LN.getInnermostLoop();
 284     EXPECT_NE(IL, nullptr);
 285     EXPECT_EQ(IL->getName(), "for.inner");
 286
 287     // Ensure the loop nest is recognized as having 2 loops.
 288     const ArrayRef<Loop *> Loops = LN.getLoops();
 289     EXPECT_EQ(Loops.size(), 2ull);
 290
 291     // Ensure the loop nest is not recognized as perfect in its entirety.
 292     const SmallVector<LoopVectorTy, 4> &PLV = LN.getPerfectLoops(SE);
 293     EXPECT_EQ(PLV.size(), 2ull);
 294     EXPECT_EQ(PLV.front().size(), 1ull);
 295     EXPECT_EQ(PLV.back().size(), 1ull);
 296
 297     // Ensure the nest depth and perfect nest depth are computed correctly.
 298     EXPECT_EQ(LN.getNestDepth(), 2u);
 299     EXPECT_EQ(LN.getMaxPerfectDepth(), 1u);
 300
 301     // Ensure enclosed instructions are recognized
 302     const LoopNest::InstrVectorTy InstrV =
 303         LN.getInterveningInstructions(OL, *IL, SE);
 304     EXPECT_EQ(InstrV.size(), 5u);
 305
 306     Instruction *SI = getInstructionByName(F, "varr")->getNextNode();
 307     Instruction *CI = SI->getNextNode();
 308     Instruction *OLH =
 309         getInstructionByName(F, "i")->getNextNode()->getNextNode();
 310     Instruction *OLL = getInstructionByName(F, "inc13")->getNextNode();
 311     Instruction *IE = getInstructionByName(F, "varr1")->getNextNode();
 312
 313     EXPECT_EQ(InstrV.front(), OLH);
 314     EXPECT_EQ(InstrV[1], OLL);
 315     EXPECT_EQ(InstrV[2], IE);
 316     EXPECT_EQ(InstrV[3], SI);
 317     EXPECT_EQ(InstrV.back(), CI);
 318   });
 319 }