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"
20 using namespace llvm;
21 
22 namespace {
23 // Hoisting the alloca instructions in the non-entry blocks to the entry
24 // block.
25 class NVPTXAllocaHoisting : public FunctionPass {
26 public:
27   static char ID; // Pass ID
NVPTXAllocaHoisting()28   NVPTXAllocaHoisting() : FunctionPass(ID) {}
29 
getAnalysisUsage(AnalysisUsage & AU) const30   void getAnalysisUsage(AnalysisUsage &AU) const override {
31     AU.addPreserved<MachineFunctionAnalysis>();
32     AU.addPreserved<StackProtector>();
33   }
34 
getPassName() const35   const char *getPassName() const override {
36     return "NVPTX specific alloca hoisting";
37   }
38 
39   bool runOnFunction(Function &function) override;
40 };
41 } // namespace
42 
runOnFunction(Function & function)43 bool 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 
61 char NVPTXAllocaHoisting::ID = 0;
62 
63 namespace llvm {
64 void initializeNVPTXAllocaHoistingPass(PassRegistry &);
65 }
66 
67 INITIALIZE_PASS(
68     NVPTXAllocaHoisting, "alloca-hoisting",
69     "Hoisting alloca instructions in non-entry blocks to the entry block",
70     false, false)
71 
createAllocaHoisting()72 FunctionPass *llvm::createAllocaHoisting() { return new NVPTXAllocaHoisting; }
73