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