1 //===- LLJITWithExecutorProcessControl.cpp - LLJIT example with EPC utils -===//
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 the lazy re-exports utility to lazily compile
10 // IR modules. We will do this in seven steps:
11 //
12 // 1. Create an LLJIT instance.
13 // 2. Install a transform so that we can see what is being compiled.
14 // 3. Create an indirect stubs manager and lazy call-through manager.
15 // 4. Add two modules that will be conditionally compiled, plus a main module.
16 // 5. Add lazy-rexports of the symbols in the conditionally compiled modules.
17 // 6. Dump the ExecutionSession state to see the symbol table prior to
18 //    executing any code.
19 // 7. Verify that only modules containing executed code are compiled.
20 //
21 //===----------------------------------------------------------------------===//
22 
23 #include "llvm/ADT/StringMap.h"
24 #include "llvm/ExecutionEngine/JITLink/JITLinkMemoryManager.h"
25 #include "llvm/ExecutionEngine/Orc/EPCIndirectionUtils.h"
26 #include "llvm/ExecutionEngine/Orc/ExecutorProcessControl.h"
27 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
28 #include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
29 #include "llvm/ExecutionEngine/Orc/OrcABISupport.h"
30 #include "llvm/Support/InitLLVM.h"
31 #include "llvm/Support/TargetSelect.h"
32 #include "llvm/Support/raw_ostream.h"
33 
34 #include "../ExampleModules.h"
35 
36 #include <future>
37 
38 using namespace llvm;
39 using namespace llvm::orc;
40 
41 ExitOnError ExitOnErr;
42 
43 // Example IR modules.
44 //
45 // Note that in the conditionally compiled modules, FooMod and BarMod, functions
46 // have been given an _body suffix. This is to ensure that their names do not
47 // clash with their lazy-reexports.
48 // For clients who do not wish to rename function bodies (e.g. because they want
49 // to re-use cached objects between static and JIT compiles) techniques exist to
50 // avoid renaming. See the lazy-reexports section of the ORCv2 design doc.
51 
52 const llvm::StringRef FooMod =
53     R"(
54   declare i32 @return1()
55 
56   define i32 @foo_body() {
57   entry:
58     %0 = call i32 @return1()
59     ret i32 %0
60   }
61 )";
62 
63 const llvm::StringRef BarMod =
64     R"(
65   declare i32 @return2()
66 
67   define i32 @bar_body() {
68   entry:
69     %0 = call i32 @return2()
70     ret i32 %0
71   }
72 )";
73 
74 const llvm::StringRef MainMod =
75     R"(
76 
77   define i32 @entry(i32 %argc) {
78   entry:
79     %and = and i32 %argc, 1
80     %tobool = icmp eq i32 %and, 0
81     br i1 %tobool, label %if.end, label %if.then
82 
83   if.then:                                          ; preds = %entry
84     %call = tail call i32 @foo() #2
85     br label %return
86 
87   if.end:                                           ; preds = %entry
88     %call1 = tail call i32 @bar() #2
89     br label %return
90 
91   return:                                           ; preds = %if.end, %if.then
92     %retval.0 = phi i32 [ %call, %if.then ], [ %call1, %if.end ]
93     ret i32 %retval.0
94   }
95 
96   declare i32 @foo()
97   declare i32 @bar()
98 )";
99 
100 extern "C" int32_t return1() { return 1; }
101 extern "C" int32_t return2() { return 2; }
102 
103 static void *reenter(void *Ctx, void *TrampolineAddr) {
104   std::promise<void *> LandingAddressP;
105   auto LandingAddressF = LandingAddressP.get_future();
106 
107   auto *EPCIU = static_cast<EPCIndirectionUtils *>(Ctx);
108   EPCIU->getLazyCallThroughManager().resolveTrampolineLandingAddress(
109       ExecutorAddr::fromPtr(TrampolineAddr), [&](ExecutorAddr LandingAddress) {
110         LandingAddressP.set_value(LandingAddress.toPtr<void *>());
111       });
112   return LandingAddressF.get();
113 }
114 
115 static void reportErrorAndExit() {
116   errs() << "Unable to lazily compile function. Exiting.\n";
117   exit(1);
118 }
119 
120 cl::list<std::string> InputArgv(cl::Positional,
121                                 cl::desc("<program arguments>..."));
122 
123 int main(int argc, char *argv[]) {
124   // Initialize LLVM.
125   InitLLVM X(argc, argv);
126 
127   InitializeNativeTarget();
128   InitializeNativeTargetAsmPrinter();
129 
130   cl::ParseCommandLineOptions(argc, argv, "LLJITWithLazyReexports");
131   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
132 
133   // (1) Create LLJIT instance.
134   auto EPC = ExitOnErr(SelfExecutorProcessControl::Create());
135   auto J = ExitOnErr(
136       LLJITBuilder().setExecutorProcessControl(std::move(EPC)).create());
137 
138   // (2) Install transform to print modules as they are compiled:
139   J->getIRTransformLayer().setTransform(
140       [](ThreadSafeModule TSM,
141          const MaterializationResponsibility &R) -> Expected<ThreadSafeModule> {
142         TSM.withModuleDo([](Module &M) { dbgs() << "---Compiling---\n" << M; });
143         return std::move(TSM); // Not a redundant move: fix build on gcc-7.5
144       });
145 
146   // (3) Create stubs and call-through managers:
147   auto EPCIU = ExitOnErr(EPCIndirectionUtils::Create(
148       J->getExecutionSession().getExecutorProcessControl()));
149   ExitOnErr(EPCIU->writeResolverBlock(ExecutorAddr::fromPtr(&reenter),
150                                       ExecutorAddr::fromPtr(EPCIU.get())));
151   EPCIU->createLazyCallThroughManager(
152       J->getExecutionSession(), ExecutorAddr::fromPtr(&reportErrorAndExit));
153   auto ISM = EPCIU->createIndirectStubsManager();
154 
155   // (4) Add modules.
156   ExitOnErr(J->addIRModule(ExitOnErr(parseExampleModule(FooMod, "foo-mod"))));
157   ExitOnErr(J->addIRModule(ExitOnErr(parseExampleModule(BarMod, "bar-mod"))));
158   ExitOnErr(J->addIRModule(ExitOnErr(parseExampleModule(MainMod, "main-mod"))));
159 
160   // (5) Add lazy reexports.
161   MangleAndInterner Mangle(J->getExecutionSession(), J->getDataLayout());
162   SymbolAliasMap ReExports(
163       {{Mangle("foo"),
164         {Mangle("foo_body"),
165          JITSymbolFlags::Exported | JITSymbolFlags::Callable}},
166        {Mangle("bar"),
167         {Mangle("bar_body"),
168          JITSymbolFlags::Exported | JITSymbolFlags::Callable}}});
169   ExitOnErr(J->getMainJITDylib().define(
170       lazyReexports(EPCIU->getLazyCallThroughManager(), *ISM,
171                     J->getMainJITDylib(), std::move(ReExports))));
172 
173   // (6) Dump the ExecutionSession state.
174   dbgs() << "---Session state---\n";
175   J->getExecutionSession().dump(dbgs());
176   dbgs() << "\n";
177 
178   // (7) Execute the JIT'd main function and pass the example's command line
179   // arguments unmodified. This should cause either ExampleMod1 or ExampleMod2
180   // to be compiled, and either "1" or "2" returned depending on the number of
181   // arguments passed.
182 
183   // Look up the JIT'd function, cast it to a function pointer, then call it.
184   auto EntryAddr = ExitOnErr(J->lookup("entry"));
185   auto *Entry = EntryAddr.toPtr<int(int)>();
186 
187   int Result = Entry(argc);
188   outs() << "---Result---\n"
189          << "entry(" << argc << ") = " << Result << "\n";
190 
191   // Destroy the EPCIndirectionUtils utility.
192   ExitOnErr(EPCIU->cleanup());
193 
194   return 0;
195 }
196