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/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(createCFGSimplificationPass());
  78   }
  79
  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
  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 }