llvm/examples/OrcV2Examples/LLJITRemovableCode/LLJITRemovableCode.cpp

   1 //===--------- LLJITRemovableCode.cpp -- LLJIT with Code Removal ----------===//
   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 the resource management APIs to transfer
  10 // ownership of modules, remove modules from a JITDylib, and then a whole
  11 // JITDylib from the ExecutionSession.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
  16 #include "llvm/IR/LegacyPassManager.h"
  17 #include "llvm/Pass.h"
  18 #include "llvm/Support/InitLLVM.h"
  19 #include "llvm/Support/TargetSelect.h"
  20 #include "llvm/Support/raw_ostream.h"
  21 #include "llvm/Transforms/IPO.h"
  22 #include "llvm/Transforms/Scalar.h"
  23
  24 #include "../ExampleModules.h"
  25
  26 using namespace llvm;
  27 using namespace llvm::orc;
  28
  29 ExitOnError ExitOnErr;
  30
  31 // Example IR modules.
  32 //
  33 // We will use a few modules containing no-op functions to demonstrate the code
  34 // removal APIs.
  35
  36 const llvm::StringRef FooMod =
  37     R"(
  38   define void @foo() {
  39   entry:
  40     ret void
  41   }
  42 )";
  43
  44 const llvm::StringRef BarMod =
  45     R"(
  46   define void @bar() {
  47   entry:
  48     ret void
  49   }
  50 )";
  51
  52 const llvm::StringRef BazMod =
  53     R"(
  54   define void @baz() {
  55   entry:
  56     ret void
  57   }
  58 )";
  59
  60 int main(int argc, char *argv[]) {
  61   // Initialize LLVM.
  62   InitLLVM X(argc, argv);
  63
  64   InitializeNativeTarget();
  65   InitializeNativeTargetAsmPrinter();
  66
  67   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
  68
  69   // (1) Create LLJIT instance.
  70   auto J = ExitOnErr(LLJITBuilder().create());
  71
  72   // (2) Create a new JITDylib to use for this example.
  73   auto &JD = ExitOnErr(J->createJITDylib("JD"));
  74
  75   // (3) Add the 'foo' module with no explicit resource tracker. The resources
  76   // for 'foo' will be tracked by the default tracker for JD. We will not be
  77   // able to free it separately, but its resources will still be freed when we
  78   // clear or remove JD.
  79   ExitOnErr(J->addIRModule(JD, ExitOnErr(parseExampleModule(FooMod, "foo"))));
  80
  81   // (4) Create a tracker for the module 'bar' and use it to add that module.
  82   auto BarRT = JD.createResourceTracker();
  83   ExitOnErr(
  84       J->addIRModule(BarRT, ExitOnErr(parseExampleModule(BarMod, "bar"))));
  85
  86   // (5) Create a tracker for the module 'baz' and use it to add that module.
  87   auto BazRT = JD.createResourceTracker();
  88   ExitOnErr(
  89       J->addIRModule(BazRT, ExitOnErr(parseExampleModule(BazMod, "baz"))));
  90
  91   // (6) Print out the symbols in their initial state:
  92   auto PrintSymbol = [&](StringRef Name) {
  93     dbgs() << Name << " = ";
  94     if (auto Sym = J->lookup(JD, Name))
  95       dbgs() << *Sym;
  96     else
  97       dbgs() << "error: " << toString(Sym.takeError()) << "\n";
  98   };
  99
 100   dbgs() << "Initially:\n";
 101   PrintSymbol("foo");
 102   PrintSymbol("bar");
 103   PrintSymbol("baz");
 104
 105   // (7) Reset BazRT. This will implicitly transfer tracking of module baz to
 106   // JD's default resource tracker.
 107   dbgs() << "After implicitly transferring ownership of baz to JD's default "
 108             "tracker:\n";
 109   BazRT = nullptr;
 110   PrintSymbol("foo");
 111   PrintSymbol("bar");
 112   PrintSymbol("baz");
 113
 114   // (8) Remove BarRT. This should remove the bar symbol.
 115   dbgs() << "After removing bar (lookup for bar should yield a missing symbol "
 116             "error):\n";
 117   ExitOnErr(BarRT->remove());
 118   PrintSymbol("foo");
 119   PrintSymbol("bar");
 120   PrintSymbol("baz");
 121
 122   // (9) Clear JD. This should remove all symbols currently in the JITDylib.
 123   dbgs() << "After clearing JD (lookup should yield missing symbol errors for "
 124             "all symbols):\n";
 125   ExitOnErr(JD.clear());
 126   PrintSymbol("foo");
 127   PrintSymbol("bar");
 128   PrintSymbol("baz");
 129
 130   // (10) Remove JD from the ExecutionSession. JD can no longer be used.
 131   dbgs() << "Removing JD.\n";
 132   ExitOnErr(J->getExecutionSession().removeJITDylib(JD));
 133
 134   dbgs() << "done.\n";
 135
 136   return 0;
 137 }