llvm/examples/OrcV2Examples/LLJITWithOptimizingIRTransform/LLJITWithOptimizingIRTransform.cpp

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