1 //===- BranchProbabilityInfoTest.cpp - BranchProbabilityInfo 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/BranchProbabilityInfo.h"
10 #include "llvm/Analysis/LoopInfo.h"
11 #include "llvm/AsmParser/Parser.h"
12 #include "llvm/IR/BasicBlock.h"
13 #include "llvm/IR/Constants.h"
14 #include "llvm/IR/Dominators.h"
15 #include "llvm/IR/Function.h"
16 #include "llvm/IR/Instructions.h"
17 #include "llvm/IR/LLVMContext.h"
18 #include "llvm/IR/Module.h"
19 #include "llvm/Support/DataTypes.h"
20 #include "llvm/Support/SourceMgr.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include "gtest/gtest.h"
23
24 namespace llvm {
25 namespace {
26
27 struct BranchProbabilityInfoTest : public testing::Test {
28 std::unique_ptr<BranchProbabilityInfo> BPI;
29 std::unique_ptr<DominatorTree> DT;
30 std::unique_ptr<LoopInfo> LI;
31 LLVMContext C;
32
buildBPIllvm::__anon5c57b6710111::BranchProbabilityInfoTest33 BranchProbabilityInfo &buildBPI(Function &F) {
34 DT.reset(new DominatorTree(F));
35 LI.reset(new LoopInfo(*DT));
36 BPI.reset(new BranchProbabilityInfo(F, *LI));
37 return *BPI;
38 }
39
makeLLVMModulellvm::__anon5c57b6710111::BranchProbabilityInfoTest40 std::unique_ptr<Module> makeLLVMModule() {
41 const char *ModuleString = "define void @f() { exit: ret void }\n";
42 SMDiagnostic Err;
43 return parseAssemblyString(ModuleString, Err, C);
44 }
45 };
46
TEST_F(BranchProbabilityInfoTest,StressUnreachableHeuristic)47 TEST_F(BranchProbabilityInfoTest, StressUnreachableHeuristic) {
48 auto M = makeLLVMModule();
49 Function *F = M->getFunction("f");
50
51 // define void @f() {
52 // entry:
53 // switch i32 undef, label %exit, [
54 // i32 0, label %preexit
55 // ... ;;< Add lots of cases to stress the heuristic.
56 // ]
57 // preexit:
58 // unreachable
59 // exit:
60 // ret void
61 // }
62
63 auto *ExitBB = &F->back();
64 auto *EntryBB = BasicBlock::Create(C, "entry", F, /*insertBefore=*/ExitBB);
65
66 auto *PreExitBB =
67 BasicBlock::Create(C, "preexit", F, /*insertBefore=*/ExitBB);
68 new UnreachableInst(C, PreExitBB);
69
70 unsigned NumCases = 4096;
71 auto *I32 = IntegerType::get(C, 32);
72 auto *Undef = UndefValue::get(I32);
73 auto *Switch = SwitchInst::Create(Undef, ExitBB, NumCases, EntryBB);
74 for (unsigned I = 0; I < NumCases; ++I)
75 Switch->addCase(ConstantInt::get(I32, I), PreExitBB);
76
77 BranchProbabilityInfo &BPI = buildBPI(*F);
78
79 // FIXME: This doesn't seem optimal. Since all of the cases handled by the
80 // switch have the *same* destination block ("preexit"), shouldn't it be the
81 // hot one? I'd expect the results to be reversed here...
82 EXPECT_FALSE(BPI.isEdgeHot(EntryBB, PreExitBB));
83 EXPECT_TRUE(BPI.isEdgeHot(EntryBB, ExitBB));
84 }
85
86 } // end anonymous namespace
87 } // end namespace llvm
88