1//===-- llvm/CodeGen/FinalizeISel.cpp ---------------------------*- 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/// This pass expands Pseudo-instructions produced by ISel, fixes register
10/// reservations and may do machine frame information adjustments.
11/// The pseudo instructions are used to allow the expansion to contain control
12/// flow, such as a conditional move implemented with a conditional branch and a
13/// phi, or an atomic operation implemented with a loop.
14//
15//===----------------------------------------------------------------------===//
16
17#include "llvm/CodeGen/FinalizeISel.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineFunctionPass.h"
21#include "llvm/CodeGen/TargetInstrInfo.h"
22#include "llvm/CodeGen/TargetLowering.h"
23#include "llvm/CodeGen/TargetSubtargetInfo.h"
24#include "llvm/InitializePasses.h"
25using namespace llvm;
26
27#define DEBUG_TYPE "finalize-isel"
28
29namespace {
30 class FinalizeISel : public MachineFunctionPass {
31 public:
32 static char ID; // Pass identification, replacement for typeid
33 FinalizeISel() : MachineFunctionPass(ID) {}
34
35 private:
36 bool runOnMachineFunction(MachineFunction &MF) override;
37
38 void getAnalysisUsage(AnalysisUsage &AU) const override {
39 MachineFunctionPass::getAnalysisUsage(AU);
40 }
41 };
42} // end anonymous namespace
43
44static std::pair<bool, bool> runImpl(MachineFunction &MF) {
45 bool Changed = false;
46 bool PreserveCFG = true;
47 const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
48 const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
49
50 TLI->finalizeLowering(MF);
51
52 // Iterate through each instruction in the function, looking for pseudos.
53 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
54 MachineBasicBlock *MBB = &*I;
55 for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
56 MBBI != MBBE; ) {
57 MachineInstr &MI = *MBBI++;
58
59 // Set AdjustsStack to true if the instruction selector emits a stack
60 // frame setup instruction or a stack aligning inlineasm.
61 if (TII->isFrameInstr(I: MI) || MI.isStackAligningInlineAsm())
62 MF.getFrameInfo().setAdjustsStack(true);
63
64 // If MI is a pseudo, expand it.
65 if (MI.usesCustomInsertionHook()) {
66 Changed = true;
67 MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
68 // The expansion may involve new basic blocks.
69 if (NewMBB != MBB) {
70 PreserveCFG = false;
71 MBB = NewMBB;
72 I = NewMBB->getIterator();
73 MBBI = NewMBB->begin();
74 MBBE = NewMBB->end();
75 }
76 }
77 }
78 }
79 return {Changed, PreserveCFG};
80}
81
82char FinalizeISel::ID = 0;
83char &llvm::FinalizeISelID = FinalizeISel::ID;
84INITIALIZE_PASS(FinalizeISel, DEBUG_TYPE,
85 "Finalize ISel and expand pseudo-instructions", false, false)
86
87bool FinalizeISel::runOnMachineFunction(MachineFunction &MF) {
88 return runImpl(MF).first;
89}
90
91PreservedAnalyses FinalizeISelPass::run(MachineFunction &MF,
92 MachineFunctionAnalysisManager &) {
93 auto [Changed, PreserveCFG] = runImpl(MF);
94 if (!Changed)
95 return PreservedAnalyses::all();
96 auto PA = getMachineFunctionPassPreservedAnalyses();
97 if (PreserveCFG)
98 PA.preserveSet<CFGAnalyses>();
99 return PA;
100}
101