1 //===--- AMDGPUMacroFusion.cpp - AMDGPU Macro Fusion ----------------------===//
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 /// \file This file contains the AMDGPU implementation of the DAG scheduling
10 ///  mutation to pair instructions back to back.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "AMDGPUMacroFusion.h"
15 #include "AMDGPUSubtarget.h"
16 #include "SIInstrInfo.h"
17 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
18 
19 #include "llvm/CodeGen/MacroFusion.h"
20 
21 using namespace llvm;
22 
23 namespace {
24 
25 /// Check if the instr pair, FirstMI and SecondMI, should be fused
26 /// together. Given SecondMI, when FirstMI is unspecified, then check if
27 /// SecondMI may be part of a fused pair at all.
28 static bool shouldScheduleAdjacent(const TargetInstrInfo &TII_,
29                                    const TargetSubtargetInfo &TSI,
30                                    const MachineInstr *FirstMI,
31                                    const MachineInstr &SecondMI) {
32   const SIInstrInfo &TII = static_cast<const SIInstrInfo&>(TII_);
33 
34   switch (SecondMI.getOpcode()) {
35   case AMDGPU::V_ADDC_U32_e64:
36   case AMDGPU::V_SUBB_U32_e64:
37   case AMDGPU::V_SUBBREV_U32_e64:
38   case AMDGPU::V_CNDMASK_B32_e64: {
39     // Try to cluster defs of condition registers to their uses. This improves
40     // the chance VCC will be available which will allow shrinking to VOP2
41     // encodings.
42     if (!FirstMI)
43       return true;
44 
45     const MachineBasicBlock &MBB = *FirstMI->getParent();
46     const MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
47     const TargetRegisterInfo *TRI = MRI.getTargetRegisterInfo();
48     const MachineOperand *Src2 = TII.getNamedOperand(SecondMI,
49                                                      AMDGPU::OpName::src2);
50     return FirstMI->definesRegister(Src2->getReg(), TRI);
51   }
52   default:
53     return false;
54   }
55 
56   return false;
57 }
58 
59 } // end namespace
60 
61 
62 namespace llvm {
63 
64 std::unique_ptr<ScheduleDAGMutation> createAMDGPUMacroFusionDAGMutation () {
65   return createMacroFusionDAGMutation(shouldScheduleAdjacent);
66 }
67 
68 } // end namespace llvm
69