unittests/Analysis/BasicAliasAnalysisTest.cpp

   1 //===- BasicAliasAnalysisTest.cpp - Unit tests for BasicAA ----------------===//
   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 // Targeted tests that are hard/convoluted to make happen with just `opt`.
  10 //
  11
  12 #include "llvm/Analysis/BasicAliasAnalysis.h"
  13 #include "llvm/Analysis/AliasAnalysis.h"
  14 #include "llvm/AsmParser/Parser.h"
  15 #include "llvm/IR/Dominators.h"
  16 #include "llvm/IR/IRBuilder.h"
  17 #include "llvm/IR/LLVMContext.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 // FIXME: This is duplicated between this file and MemorySSATest. Refactor.
  25 const static char DLString[] = "e-i64:64-f80:128-n8:16:32:64-S128";
  26
  27 /// There's a lot of common setup between these tests. This fixture helps reduce
  28 /// that. Tests should mock up a function, store it in F, and then call
  29 /// setupAnalyses().
  30 class BasicAATest : public testing::Test {
  31 protected:
  32   // N.B. Many of these members depend on each other (e.g. the Module depends on
  33   // the Context, etc.). So, order matters here (and in TestAnalyses).
  34   LLVMContext C;
  35   Module M;
  36   IRBuilder<> B;
  37   DataLayout DL;
  38   TargetLibraryInfoImpl TLII;
  39   TargetLibraryInfo TLI;
  40   Function *F;
  41
  42   // Things that we need to build after the function is created.
  43   struct TestAnalyses {
  44     DominatorTree DT;
  45     AssumptionCache AC;
  46     BasicAAResult BAA;
  47
  48     TestAnalyses(BasicAATest &Test)
  49         : DT(*Test.F), AC(*Test.F), BAA(Test.DL, *Test.F, Test.TLI, AC, &DT) {}
  50   };
  51
  52   llvm::Optional<TestAnalyses> Analyses;
  53
  54   BasicAAResult &setupAnalyses() {
  55     assert(F);
  56     Analyses.emplace(*this);
  57     return Analyses->BAA;
  58   }
  59
  60 public:
  61   BasicAATest()
  62       : M("BasicAATest", C), B(C), DL(DLString), TLI(TLII), F(nullptr) {}
  63 };
  64
  65 // Check that a function arg can't trivially alias a global when we're accessing
  66 // >sizeof(global) bytes through that arg, unless the access size is just an
  67 // upper-bound.
  68 TEST_F(BasicAATest, AliasInstWithObjectOfImpreciseSize) {
  69   F = Function::Create(
  70       FunctionType::get(B.getVoidTy(), {B.getInt32Ty()->getPointerTo()}, false),
  71       GlobalValue::ExternalLinkage, "F", &M);
  72
  73   BasicBlock *Entry(BasicBlock::Create(C, "", F));
  74   B.SetInsertPoint(Entry);
  75
  76   Value *IncomingI32Ptr = F->arg_begin();
  77
  78   auto *GlobalPtr =
  79       cast<GlobalVariable>(M.getOrInsertGlobal("some_global", B.getInt8Ty()));
  80
  81   // Without sufficiently restricted linkage/an init, some of the object size
  82   // checking bits get more conservative.
  83   GlobalPtr->setLinkage(GlobalValue::LinkageTypes::InternalLinkage);
  84   GlobalPtr->setInitializer(B.getInt8(0));
  85
  86   BasicAAResult &BasicAA = setupAnalyses();
  87   ASSERT_EQ(
  88       BasicAA.alias(MemoryLocation(IncomingI32Ptr, LocationSize::precise(4)),
  89                     MemoryLocation(GlobalPtr, LocationSize::precise(1))),
  90       AliasResult::NoAlias);
  91
  92   ASSERT_EQ(
  93       BasicAA.alias(MemoryLocation(IncomingI32Ptr, LocationSize::upperBound(4)),
  94                     MemoryLocation(GlobalPtr, LocationSize::precise(1))),
  95       AliasResult::MayAlias);
  96 }
  97
  98 // Check that we fall back to MayAlias if we see an access of an entire object
  99 // that's just an upper-bound.
 100 TEST_F(BasicAATest, AliasInstWithFullObjectOfImpreciseSize) {
 101   F = Function::Create(
 102       FunctionType::get(B.getVoidTy(), {B.getInt64Ty()}, false),
 103       GlobalValue::ExternalLinkage, "F", &M);
 104
 105   BasicBlock *Entry(BasicBlock::Create(C, "", F));
 106   B.SetInsertPoint(Entry);
 107
 108   Value *ArbitraryI32 = F->arg_begin();
 109   AllocaInst *I8 = B.CreateAlloca(B.getInt8Ty(), B.getInt32(2));
 110   auto *I8AtUncertainOffset =
 111       cast<GetElementPtrInst>(B.CreateGEP(B.getInt8Ty(), I8, ArbitraryI32));
 112
 113   BasicAAResult &BasicAA = setupAnalyses();
 114   ASSERT_EQ(BasicAA.alias(
 115                 MemoryLocation(I8, LocationSize::precise(2)),
 116                 MemoryLocation(I8AtUncertainOffset, LocationSize::precise(1))),
 117             AliasResult::PartialAlias);
 118
 119   ASSERT_EQ(BasicAA.alias(
 120                 MemoryLocation(I8, LocationSize::upperBound(2)),
 121                 MemoryLocation(I8AtUncertainOffset, LocationSize::precise(1))),
 122             AliasResult::MayAlias);
 123 }