1 //===------ LeonPasses.cpp - Define passes specific to LEON ---------------===//
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 //
10 //===----------------------------------------------------------------------===//
11 
12 #include "LeonPasses.h"
13 #include "SparcSubtarget.h"
14 #include "llvm/CodeGen/MachineBasicBlock.h"
15 #include "llvm/CodeGen/MachineFunction.h"
16 #include "llvm/CodeGen/MachineInstr.h"
17 #include "llvm/CodeGen/MachineInstrBuilder.h"
18 #include "llvm/Support/raw_ostream.h"
19 
20 using namespace llvm;
21 
22 LEONMachineFunctionPass::LEONMachineFunctionPass(char &ID)
23     : MachineFunctionPass(ID) {}
24 
25 //*****************************************************************************
26 //**** InsertNOPLoad pass
27 //*****************************************************************************
28 // This pass fixes the incorrectly working Load instructions that exists for
29 // some earlier versions of the LEON processor line. NOP instructions must
30 // be inserted after the load instruction to ensure that the Load instruction
31 // behaves as expected for these processors.
32 //
33 // This pass inserts a NOP after any LD or LDF instruction.
34 //
35 char InsertNOPLoad::ID = 0;
36 
37 InsertNOPLoad::InsertNOPLoad() : LEONMachineFunctionPass(ID) {}
38 
39 bool InsertNOPLoad::runOnMachineFunction(MachineFunction &MF) {
40   Subtarget = &MF.getSubtarget<SparcSubtarget>();
41   const TargetInstrInfo &TII = *Subtarget->getInstrInfo();
42   DebugLoc DL = DebugLoc();
43 
44   bool Modified = false;
45   for (MachineBasicBlock &MBB : MF) {
46     for (auto MBBI = MBB.begin(), E = MBB.end(); MBBI != E; ++MBBI) {
47       MachineInstr &MI = *MBBI;
48       unsigned Opcode = MI.getOpcode();
49       if (Opcode >= SP::LDDArr && Opcode <= SP::LDrr) {
50         MachineBasicBlock::iterator NMBBI = std::next(MBBI);
51         BuildMI(MBB, NMBBI, DL, TII.get(SP::NOP));
52         Modified = true;
53       }
54     }
55   }
56 
57   return Modified;
58 }
59 
60 
61 
62 //*****************************************************************************
63 //**** DetectRoundChange pass
64 //*****************************************************************************
65 // To prevent any explicit change of the default rounding mode, this pass
66 // detects any call of the fesetround function.
67 // A warning is generated to ensure the user knows this has happened.
68 //
69 // Detects an erratum in UT699 LEON 3 processor
70 
71 char DetectRoundChange::ID = 0;
72 
73 DetectRoundChange::DetectRoundChange() : LEONMachineFunctionPass(ID) {}
74 
75 bool DetectRoundChange::runOnMachineFunction(MachineFunction &MF) {
76   Subtarget = &MF.getSubtarget<SparcSubtarget>();
77 
78   bool Modified = false;
79   for (MachineBasicBlock &MBB : MF) {
80     for (MachineInstr &MI : MBB) {
81       unsigned Opcode = MI.getOpcode();
82       if (Opcode == SP::CALL && MI.getNumOperands() > 0) {
83         MachineOperand &MO = MI.getOperand(0);
84 
85         if (MO.isGlobal()) {
86           StringRef FuncName = MO.getGlobal()->getName();
87           if (FuncName.compare_insensitive("fesetround") == 0) {
88             errs() << "Error: You are using the detectroundchange "
89                       "option to detect rounding changes that will "
90                       "cause LEON errata. The only way to fix this "
91                       "is to remove the call to fesetround from "
92                       "the source code.\n";
93           }
94         }
95       }
96     }
97   }
98 
99   return Modified;
100 }
101 
102 //*****************************************************************************
103 //**** FixAllFDIVSQRT pass
104 //*****************************************************************************
105 // This pass fixes the incorrectly working FDIVx and FSQRTx instructions that
106 // exist for some earlier versions of the LEON processor line. Five NOP
107 // instructions need to be inserted after these instructions to ensure the
108 // correct result is placed in the destination registers before they are used.
109 //
110 // This pass implements two fixes:
111 //  1) fixing the FSQRTS and FSQRTD instructions.
112 //  2) fixing the FDIVS and FDIVD instructions.
113 //
114 // FSQRTS and FDIVS are converted to FDIVD and FSQRTD respectively earlier in
115 // the pipeline when this option is enabled, so this pass needs only to deal
116 // with the changes that still need implementing for the "double" versions
117 // of these instructions.
118 //
119 char FixAllFDIVSQRT::ID = 0;
120 
121 FixAllFDIVSQRT::FixAllFDIVSQRT() : LEONMachineFunctionPass(ID) {}
122 
123 bool FixAllFDIVSQRT::runOnMachineFunction(MachineFunction &MF) {
124   Subtarget = &MF.getSubtarget<SparcSubtarget>();
125   const TargetInstrInfo &TII = *Subtarget->getInstrInfo();
126   DebugLoc DL = DebugLoc();
127 
128   bool Modified = false;
129   for (MachineBasicBlock &MBB : MF) {
130     for (auto MBBI = MBB.begin(), E = MBB.end(); MBBI != E; ++MBBI) {
131       MachineInstr &MI = *MBBI;
132       unsigned Opcode = MI.getOpcode();
133 
134       // Note: FDIVS and FSQRTS cannot be generated when this erratum fix is
135       // switched on so we don't need to check for them here. They will
136       // already have been converted to FSQRTD or FDIVD earlier in the
137       // pipeline.
138       if (Opcode == SP::FSQRTD || Opcode == SP::FDIVD) {
139         for (int InsertedCount = 0; InsertedCount < 5; InsertedCount++)
140           BuildMI(MBB, MBBI, DL, TII.get(SP::NOP));
141 
142         MachineBasicBlock::iterator NMBBI = std::next(MBBI);
143         for (int InsertedCount = 0; InsertedCount < 28; InsertedCount++)
144           BuildMI(MBB, NMBBI, DL, TII.get(SP::NOP));
145 
146         Modified = true;
147       }
148     }
149   }
150 
151   return Modified;
152 }
153