1 //===-- LLJITWithOptimizingIRTransform.cpp -- LLJIT with IR optimization --===//
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 // In this example we will use an IR transform to optimize a module as it
10 // passes through LLJIT's IRTransformLayer.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
15 #include "llvm/IR/LegacyPassManager.h"
16 #include "llvm/Pass.h"
17 #include "llvm/Support/InitLLVM.h"
18 #include "llvm/Support/TargetSelect.h"
19 #include "llvm/Support/raw_ostream.h"
20 #include "llvm/Transforms/IPO.h"
21 #include "llvm/Transforms/Scalar.h"
22 
23 #include "../ExampleModules.h"
24 
25 using namespace llvm;
26 using namespace llvm::orc;
27 
28 ExitOnError ExitOnErr;
29 
30 // Example IR module.
31 //
32 // This IR contains a recursive definition of the factorial function:
33 //
34 // fac(n) | n == 0    = 1
35 //        | otherwise = n * fac(n - 1)
36 //
37 // It also contains an entry function which calls the factorial function with
38 // an input value of 5.
39 //
40 // We expect the IR optimization transform that we build below to transform
41 // this into a non-recursive factorial function and an entry function that
42 // returns a constant value of 5!, or 120.
43 
44 const llvm::StringRef MainMod =
45     R"(
46 
47   define i32 @fac(i32 %n) {
48   entry:
49     %tobool = icmp eq i32 %n, 0
50     br i1 %tobool, label %return, label %if.then
51 
52   if.then:                                          ; preds = %entry
53     %arg = add nsw i32 %n, -1
54     %call_result = call i32 @fac(i32 %arg)
55     %result = mul nsw i32 %n, %call_result
56     br label %return
57 
58   return:                                           ; preds = %entry, %if.then
59     %final_result = phi i32 [ %result, %if.then ], [ 1, %entry ]
60     ret i32 %final_result
61   }
62 
63   define i32 @entry() {
64   entry:
65     %result = call i32 @fac(i32 5)
66     ret i32 %result
67   }
68 
69 )";
70 
71 // A function object that creates a simple pass pipeline to apply to each
72 // module as it passes through the IRTransformLayer.
73 class MyOptimizationTransform {
74 public:
75   MyOptimizationTransform() : PM(std::make_unique<legacy::PassManager>()) {
76     PM->add(createTailCallEliminationPass());
77     PM->add(createFunctionInliningPass());
78     PM->add(createIndVarSimplifyPass());
79     PM->add(createCFGSimplificationPass());
80   }
81 
82   Expected<ThreadSafeModule> operator()(ThreadSafeModule TSM,
83                                         MaterializationResponsibility &R) {
84     TSM.withModuleDo([this](Module &M) {
85       dbgs() << "--- BEFORE OPTIMIZATION ---\n" << M << "\n";
86       PM->run(M);
87       dbgs() << "--- AFTER OPTIMIZATION ---\n" << M << "\n";
88     });
89     return std::move(TSM);
90   }
91 
92 private:
93   std::unique_ptr<legacy::PassManager> PM;
94 };
95 
96 int main(int argc, char *argv[]) {
97   // Initialize LLVM.
98   InitLLVM X(argc, argv);
99 
100   InitializeNativeTarget();
101   InitializeNativeTargetAsmPrinter();
102 
103   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
104 
105   // (1) Create LLJIT instance.
106   auto J = ExitOnErr(LLJITBuilder().create());
107 
108   // (2) Install transform to optimize modules when they're materialized.
109   J->getIRTransformLayer().setTransform(MyOptimizationTransform());
110 
111   // (3) Add modules.
112   ExitOnErr(J->addIRModule(ExitOnErr(parseExampleModule(MainMod, "MainMod"))));
113 
114   // (4) Look up the JIT'd function and call it.
115   auto EntrySym = ExitOnErr(J->lookup("entry"));
116   auto *Entry = (int (*)())EntrySym.getAddress();
117 
118   int Result = Entry();
119   outs() << "--- Result ---\n"
120          << "entry() = " << Result << "\n";
121 
122   return 0;
123 }
124