1//===-- AllocaHoisting.cpp - Hoist allocas to the entry block --*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// Hoist the alloca instructions in the non-entry blocks to the entry blocks.
11//
12//===----------------------------------------------------------------------===//
13
14#include "NVPTXAllocaHoisting.h"
15#include "llvm/CodeGen/MachineFunctionAnalysis.h"
16#include "llvm/CodeGen/StackProtector.h"
17#include "llvm/IR/Constants.h"
18#include "llvm/IR/Function.h"
19#include "llvm/IR/Instructions.h"
20using namespace llvm;
21
22namespace {
23// Hoisting the alloca instructions in the non-entry blocks to the entry
24// block.
25class NVPTXAllocaHoisting : public FunctionPass {
26public:
27  static char ID; // Pass ID
28  NVPTXAllocaHoisting() : FunctionPass(ID) {}
29
30  void getAnalysisUsage(AnalysisUsage &AU) const override {
31    AU.addPreserved<MachineFunctionAnalysis>();
32    AU.addPreserved<StackProtector>();
33  }
34
35  const char *getPassName() const override {
36    return "NVPTX specific alloca hoisting";
37  }
38
39  bool runOnFunction(Function &function) override;
40};
41} // namespace
42
43bool NVPTXAllocaHoisting::runOnFunction(Function &function) {
44  bool functionModified = false;
45  Function::iterator I = function.begin();
46  TerminatorInst *firstTerminatorInst = (I++)->getTerminator();
47
48  for (Function::iterator E = function.end(); I != E; ++I) {
49    for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) {
50      AllocaInst *allocaInst = dyn_cast<AllocaInst>(BI++);
51      if (allocaInst && isa<ConstantInt>(allocaInst->getArraySize())) {
52        allocaInst->moveBefore(firstTerminatorInst);
53        functionModified = true;
54      }
55    }
56  }
57
58  return functionModified;
59}
60
61char NVPTXAllocaHoisting::ID = 0;
62
63namespace llvm {
64void initializeNVPTXAllocaHoistingPass(PassRegistry &);
65}
66
67INITIALIZE_PASS(
68    NVPTXAllocaHoisting, "alloca-hoisting",
69    "Hoisting alloca instructions in non-entry blocks to the entry block",
70    false, false)
71
72FunctionPass *llvm::createAllocaHoisting() { return new NVPTXAllocaHoisting; }
73