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 "NVPTX.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
20static bool hoistAllocas(Function &function) {
21 bool functionModified = false;
22 Function::iterator I = function.begin();
23 Instruction *firstTerminatorInst = (I++)->getTerminator();
24
25 for (Function::iterator E = function.end(); I != E; ++I) {
26 for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) {
27 AllocaInst *allocaInst = dyn_cast<AllocaInst>(Val: BI++);
28 if (allocaInst && isa<ConstantInt>(Val: allocaInst->getArraySize())) {
29 allocaInst->moveBefore(InsertPos: firstTerminatorInst->getIterator());
30 functionModified = true;
31 }
32 }
33 }
34
35 return functionModified;
36}
37
38namespace {
39// Hoisting the alloca instructions in the non-entry blocks to the entry
40// block.
41class NVPTXAllocaHoistingLegacyPass : public FunctionPass {
42public:
43 static char ID; // Pass ID
44 NVPTXAllocaHoistingLegacyPass() : FunctionPass(ID) {}
45
46 void getAnalysisUsage(AnalysisUsage &AU) const override {
47 AU.setPreservesCFG();
48 AU.addPreserved<StackProtector>();
49 }
50
51 StringRef getPassName() const override {
52 return "NVPTX specific alloca hoisting";
53 }
54
55 bool runOnFunction(Function &function) override {
56 return hoistAllocas(function);
57 }
58};
59} // namespace
60
61char NVPTXAllocaHoistingLegacyPass::ID = 0;
62
63INITIALIZE_PASS(
64 NVPTXAllocaHoistingLegacyPass, "alloca-hoisting",
65 "Hoisting alloca instructions in non-entry blocks to the entry block",
66 false, false)
67
68FunctionPass *llvm::createNVPTXAllocaHoistingLegacyPass() {
69 return new NVPTXAllocaHoistingLegacyPass;
70}
71
72PreservedAnalyses NVPTXAllocaHoistingPass::run(Function &F,
73 FunctionAnalysisManager &FAM) {
74 if (!hoistAllocas(function&: F))
75 return PreservedAnalyses::all();
76 PreservedAnalyses PA;
77 PA.preserveSet<CFGAnalyses>();
78 PA.preserve<SSPLayoutAnalysis>();
79 return PA;
80}
81