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"
25 using namespace llvm;
26
27 #define DEBUG_TYPE "finalize-isel"
28
29 namespace {
30 class FinalizeISel : public MachineFunctionPass {
31 public:
32 static char ID; // Pass identification, replacement for typeid
FinalizeISel()33 FinalizeISel() : MachineFunctionPass(ID) {}
34
35 private:
36 bool runOnMachineFunction(MachineFunction &MF) override;
37
getAnalysisUsage(AnalysisUsage & AU) const38 void getAnalysisUsage(AnalysisUsage &AU) const override {
39 MachineFunctionPass::getAnalysisUsage(AU);
40 }
41 };
42 } // end anonymous namespace
43
runImpl(MachineFunction & MF)44 static 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 // Iterate through each instruction in the function, looking for pseudos.
51 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
52 MachineBasicBlock *MBB = &*I;
53 for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
54 MBBI != MBBE; ) {
55 MachineInstr &MI = *MBBI++;
56
57 // Set AdjustsStack to true if the instruction selector emits a stack
58 // frame setup instruction or a stack aligning inlineasm.
59 if (TII->isFrameInstr(MI) || MI.isStackAligningInlineAsm())
60 MF.getFrameInfo().setAdjustsStack(true);
61
62 // If MI is a pseudo, expand it.
63 if (MI.usesCustomInsertionHook()) {
64 Changed = true;
65 MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
66 // The expansion may involve new basic blocks.
67 if (NewMBB != MBB) {
68 PreserveCFG = false;
69 MBB = NewMBB;
70 I = NewMBB->getIterator();
71 MBBI = NewMBB->begin();
72 MBBE = NewMBB->end();
73 }
74 }
75 }
76 }
77
78 TLI->finalizeLowering(MF);
79
80 return {Changed, PreserveCFG};
81 }
82
83 char FinalizeISel::ID = 0;
84 char &llvm::FinalizeISelID = FinalizeISel::ID;
85 INITIALIZE_PASS(FinalizeISel, DEBUG_TYPE,
86 "Finalize ISel and expand pseudo-instructions", false, false)
87
runOnMachineFunction(MachineFunction & MF)88 bool FinalizeISel::runOnMachineFunction(MachineFunction &MF) {
89 return runImpl(MF).first;
90 }
91
run(MachineFunction & MF,MachineFunctionAnalysisManager &)92 PreservedAnalyses FinalizeISelPass::run(MachineFunction &MF,
93 MachineFunctionAnalysisManager &) {
94 auto [Changed, PreserveCFG] = runImpl(MF);
95 if (!Changed)
96 return PreservedAnalyses::all();
97 auto PA = getMachineFunctionPassPreservedAnalyses();
98 if (PreserveCFG)
99 PA.preserveSet<CFGAnalyses>();
100 return PA;
101 }
102