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/MachineFunction.h"
18 #include "llvm/CodeGen/MachineFunctionPass.h"
19 #include "llvm/CodeGen/Passes.h"
20 #include "llvm/CodeGen/TargetLowering.h"
21 #include "llvm/CodeGen/TargetSubtargetInfo.h"
22 #include "llvm/InitializePasses.h"
23 #include "llvm/Support/Debug.h"
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "finalize-isel"
27 
28 namespace {
29   class FinalizeISel : public MachineFunctionPass {
30   public:
31     static char ID; // Pass identification, replacement for typeid
FinalizeISel()32     FinalizeISel() : MachineFunctionPass(ID) {}
33 
34   private:
35     bool runOnMachineFunction(MachineFunction &MF) override;
36 
getAnalysisUsage(AnalysisUsage & AU) const37     void getAnalysisUsage(AnalysisUsage &AU) const override {
38       MachineFunctionPass::getAnalysisUsage(AU);
39     }
40   };
41 } // end anonymous namespace
42 
43 char FinalizeISel::ID = 0;
44 char &llvm::FinalizeISelID = FinalizeISel::ID;
45 INITIALIZE_PASS(FinalizeISel, DEBUG_TYPE,
46                 "Finalize ISel and expand pseudo-instructions", false, false)
47 
runOnMachineFunction(MachineFunction & MF)48 bool FinalizeISel::runOnMachineFunction(MachineFunction &MF) {
49   bool Changed = false;
50   const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
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       // If MI is a pseudo, expand it.
60       if (MI.usesCustomInsertionHook()) {
61         Changed = true;
62         MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
63         // The expansion may involve new basic blocks.
64         if (NewMBB != MBB) {
65           MBB = NewMBB;
66           I = NewMBB->getIterator();
67           MBBI = NewMBB->begin();
68           MBBE = NewMBB->end();
69         }
70       }
71     }
72   }
73 
74   TLI->finalizeLowering(MF);
75 
76   return Changed;
77 }
78