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"
18using namespace llvm;
19
20namespace {
21// Hoisting the alloca instructions in the non-entry blocks to the entry
22// block.
23class NVPTXAllocaHoisting : public FunctionPass {
24public:
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
40bool 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>(Val: BI++);
48 if (allocaInst && isa<ConstantInt>(Val: allocaInst->getArraySize())) {
49 allocaInst->moveBefore(MovePos: firstTerminatorInst);
50 functionModified = true;
51 }
52 }
53 }
54
55 return functionModified;
56}
57
58char NVPTXAllocaHoisting::ID = 0;
59
60namespace llvm {
61void initializeNVPTXAllocaHoistingPass(PassRegistry &);
62}
63
64INITIALIZE_PASS(
65 NVPTXAllocaHoisting, "alloca-hoisting",
66 "Hoisting alloca instructions in non-entry blocks to the entry block",
67 false, false)
68
69FunctionPass *llvm::createAllocaHoisting() { return new NVPTXAllocaHoisting; }
70