1 //===- ARMMacroFusion.cpp - ARM Macro Fusion ----------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 /// \file This file contains the ARM implementation of the DAG scheduling
11 ///  mutation to pair instructions back to back.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ARMMacroFusion.h"
16 #include "ARMSubtarget.h"
17 #include "llvm/CodeGen/MacroFusion.h"
18 #include "llvm/CodeGen/TargetInstrInfo.h"
19 
20 namespace llvm {
21 
22 // Fuse AES crypto encoding or decoding.
23 static bool isAESPair(const MachineInstr *FirstMI,
24                       const MachineInstr &SecondMI) {
25   // Assume the 1st instr to be a wildcard if it is unspecified.
26   unsigned FirstOpcode =
27       FirstMI ? FirstMI->getOpcode()
28               : static_cast<unsigned>(ARM::INSTRUCTION_LIST_END);
29   unsigned SecondOpcode = SecondMI.getOpcode();
30 
31   switch(SecondOpcode) {
32   // AES encode.
33   case ARM::AESMC :
34     return FirstOpcode == ARM::AESE ||
35            FirstOpcode == ARM::INSTRUCTION_LIST_END;
36   // AES decode.
37   case ARM::AESIMC:
38     return FirstOpcode == ARM::AESD ||
39            FirstOpcode == ARM::INSTRUCTION_LIST_END;
40   }
41 
42   return false;
43 }
44 
45 // Fuse literal generation.
46 static bool isLiteralsPair(const MachineInstr *FirstMI,
47                            const MachineInstr &SecondMI) {
48   // Assume the 1st instr to be a wildcard if it is unspecified.
49   unsigned FirstOpcode =
50       FirstMI ? FirstMI->getOpcode()
51               : static_cast<unsigned>(ARM::INSTRUCTION_LIST_END);
52   unsigned SecondOpcode = SecondMI.getOpcode();
53 
54   // 32 bit immediate.
55   if ((FirstOpcode == ARM::INSTRUCTION_LIST_END ||
56        FirstOpcode == ARM::MOVi16) &&
57       SecondOpcode == ARM::MOVTi16)
58     return true;
59 
60   return false;
61 }
62 
63 /// Check if the instr pair, FirstMI and SecondMI, should be fused
64 /// together. Given SecondMI, when FirstMI is unspecified, then check if
65 /// SecondMI may be part of a fused pair at all.
66 static bool shouldScheduleAdjacent(const TargetInstrInfo &TII,
67                                    const TargetSubtargetInfo &TSI,
68                                    const MachineInstr *FirstMI,
69                                    const MachineInstr &SecondMI) {
70   const ARMSubtarget &ST = static_cast<const ARMSubtarget&>(TSI);
71 
72   if (ST.hasFuseAES() && isAESPair(FirstMI, SecondMI))
73     return true;
74   if (ST.hasFuseLiterals() && isLiteralsPair(FirstMI, SecondMI))
75     return true;
76 
77   return false;
78 }
79 
80 std::unique_ptr<ScheduleDAGMutation> createARMMacroFusionDAGMutation () {
81   return createMacroFusionDAGMutation(shouldScheduleAdjacent);
82 }
83 
84 } // end namespace llvm
85