llvm/lib/Target/NVPTX/NVPTXAllocaHoisting.cpp

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