LLVM  10.0.0svn
Hello.cpp
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1 //===- Hello.cpp - Example code from "Writing an LLVM Pass" ---------------===//
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 // This file implements two versions of the LLVM "Hello World" pass described
10 // in docs/WritingAnLLVMPass.html
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/Statistic.h"
15 #include "llvm/IR/Function.h"
16 #include "llvm/Pass.h"
18 using namespace llvm;
19 
20 #define DEBUG_TYPE "hello"
21 
22 STATISTIC(HelloCounter, "Counts number of functions greeted");
23 
24 namespace {
25  // Hello - The first implementation, without getAnalysisUsage.
26  struct Hello : public FunctionPass {
27  static char ID; // Pass identification, replacement for typeid
28  Hello() : FunctionPass(ID) {}
29 
30  bool runOnFunction(Function &F) override {
31  ++HelloCounter;
32  errs() << "Hello: ";
33  errs().write_escaped(F.getName()) << '\n';
34  return false;
35  }
36  };
37 }
38 
39 char Hello::ID = 0;
40 static RegisterPass<Hello> X("hello", "Hello World Pass");
41 
42 namespace {
43  // Hello2 - The second implementation with getAnalysisUsage implemented.
44  struct Hello2 : public FunctionPass {
45  static char ID; // Pass identification, replacement for typeid
46  Hello2() : FunctionPass(ID) {}
47 
48  bool runOnFunction(Function &F) override {
49  ++HelloCounter;
50  errs() << "Hello: ";
51  errs().write_escaped(F.getName()) << '\n';
52  return false;
53  }
54 
55  // We don't modify the program, so we preserve all analyses.
56  void getAnalysisUsage(AnalysisUsage &AU) const override {
57  AU.setPreservesAll();
58  }
59  };
60 }
61 
62 char Hello2::ID = 0;
64 Y("hello2", "Hello World Pass (with getAnalysisUsage implemented)");
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
RegisterPass<t> template - This template class is used to notify the system that a Pass is available ...
Definition: PassSupport.h:90
This class represents lattice values for constants.
Definition: AllocatorList.h:23
static RegisterPass< Hello > X("hello", "Hello World Pass")
STATISTIC(NumFunctions, "Total number of functions")
F(f)
static bool runOnFunction(Function &F, bool PostInlining)
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
raw_ostream & write_escaped(StringRef Str, bool UseHexEscapes=false)
Output Str, turning &#39;\&#39;, &#39;&#39;, &#39; &#39;, &#39;"&#39;, and anything that doesn&#39;t satisfy llvm::isPrint into an escape...
void setPreservesAll()
Set by analyses that do not transform their input at all.
static RegisterPass< Hello2 > Y("hello2", "Hello World Pass (with getAnalysisUsage implemented)")
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214