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:
MyOptimizationTransform()75 MyOptimizationTransform() : PM(std::make_unique<legacy::PassManager>()) {
76 PM->add(createTailCallEliminationPass());
77 PM->add(createCFGSimplificationPass());
78 }
79
operator ()(ThreadSafeModule TSM,MaterializationResponsibility & R)80 Expected<ThreadSafeModule> operator()(ThreadSafeModule TSM,
81 MaterializationResponsibility &R) {
82 TSM.withModuleDo([this](Module &M) {
83 dbgs() << "--- BEFORE OPTIMIZATION ---\n" << M << "\n";
84 PM->run(M);
85 dbgs() << "--- AFTER OPTIMIZATION ---\n" << M << "\n";
86 });
87 return std::move(TSM);
88 }
89
90 private:
91 std::unique_ptr<legacy::PassManager> PM;
92 };
93
main(int argc,char * argv[])94 int main(int argc, char *argv[]) {
95 // Initialize LLVM.
96 InitLLVM X(argc, argv);
97
98 InitializeNativeTarget();
99 InitializeNativeTargetAsmPrinter();
100
101 ExitOnErr.setBanner(std::string(argv[0]) + ": ");
102
103 // (1) Create LLJIT instance.
104 auto J = ExitOnErr(LLJITBuilder().create());
105
106 // (2) Install transform to optimize modules when they're materialized.
107 J->getIRTransformLayer().setTransform(MyOptimizationTransform());
108
109 // (3) Add modules.
110 ExitOnErr(J->addIRModule(ExitOnErr(parseExampleModule(MainMod, "MainMod"))));
111
112 // (4) Look up the JIT'd function and call it.
113 auto EntryAddr = ExitOnErr(J->lookup("entry"));
114 auto *Entry = EntryAddr.toPtr<int()>();
115
116 int Result = Entry();
117 outs() << "--- Result ---\n"
118 << "entry() = " << Result << "\n";
119
120 return 0;
121 }
122