1 //===-- SILowerI1Copies.cpp - Lower I1 Copies -----------------------------===//
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 /// i1 values are usually inserted by the CFG Structurize pass and they are
9 /// unique in that they can be copied from VALU to SALU registers.
10 /// This is not possible for any other value type.  Since there are no
11 /// MOV instructions for i1, we to use V_CMP_* and V_CNDMASK to move the i1.
12 ///
13 //===----------------------------------------------------------------------===//
14 //
15 
16 #define DEBUG_TYPE "si-i1-copies"
17 #include "AMDGPU.h"
18 #include "AMDGPUSubtarget.h"
19 #include "SIInstrInfo.h"
20 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
21 #include "llvm/CodeGen/MachineDominators.h"
22 #include "llvm/CodeGen/MachineFunctionPass.h"
23 #include "llvm/CodeGen/MachineInstrBuilder.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/IR/LLVMContext.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Target/TargetMachine.h"
29 
30 using namespace llvm;
31 
32 namespace {
33 
34 class SILowerI1Copies : public MachineFunctionPass {
35 public:
36   static char ID;
37 
38 public:
SILowerI1Copies()39   SILowerI1Copies() : MachineFunctionPass(ID) {
40     initializeSILowerI1CopiesPass(*PassRegistry::getPassRegistry());
41   }
42 
43   bool runOnMachineFunction(MachineFunction &MF) override;
44 
getPassName() const45   const char *getPassName() const override {
46     return "SI Lower i1 Copies";
47   }
48 
getAnalysisUsage(AnalysisUsage & AU) const49   void getAnalysisUsage(AnalysisUsage &AU) const override {
50     AU.addRequired<MachineDominatorTree>();
51     AU.addPreserved<MachineDominatorTree>();
52     AU.setPreservesCFG();
53     MachineFunctionPass::getAnalysisUsage(AU);
54   }
55 };
56 
57 } // End anonymous namespace.
58 
59 INITIALIZE_PASS_BEGIN(SILowerI1Copies, DEBUG_TYPE,
60                       "SI Lower i1 Copies", false, false)
61 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
62 INITIALIZE_PASS_END(SILowerI1Copies, DEBUG_TYPE,
63                     "SI Lower i1 Copies", false, false)
64 
65 char SILowerI1Copies::ID = 0;
66 
67 char &llvm::SILowerI1CopiesID = SILowerI1Copies::ID;
68 
createSILowerI1CopiesPass()69 FunctionPass *llvm::createSILowerI1CopiesPass() {
70   return new SILowerI1Copies();
71 }
72 
runOnMachineFunction(MachineFunction & MF)73 bool SILowerI1Copies::runOnMachineFunction(MachineFunction &MF) {
74   MachineRegisterInfo &MRI = MF.getRegInfo();
75   const SIInstrInfo *TII =
76       static_cast<const SIInstrInfo *>(MF.getSubtarget().getInstrInfo());
77   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
78   std::vector<unsigned> I1Defs;
79 
80   for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
81                                                   BI != BE; ++BI) {
82 
83     MachineBasicBlock &MBB = *BI;
84     MachineBasicBlock::iterator I, Next;
85     for (I = MBB.begin(); I != MBB.end(); I = Next) {
86       Next = std::next(I);
87       MachineInstr &MI = *I;
88 
89       if (MI.getOpcode() == AMDGPU::IMPLICIT_DEF) {
90         unsigned Reg = MI.getOperand(0).getReg();
91         const TargetRegisterClass *RC = MRI.getRegClass(Reg);
92         if (RC == &AMDGPU::VReg_1RegClass)
93           MRI.setRegClass(Reg, &AMDGPU::SReg_64RegClass);
94         continue;
95       }
96 
97       if (MI.getOpcode() != AMDGPU::COPY)
98         continue;
99 
100       const MachineOperand &Dst = MI.getOperand(0);
101       const MachineOperand &Src = MI.getOperand(1);
102 
103       if (!TargetRegisterInfo::isVirtualRegister(Src.getReg()) ||
104           !TargetRegisterInfo::isVirtualRegister(Dst.getReg()))
105         continue;
106 
107       const TargetRegisterClass *DstRC = MRI.getRegClass(Dst.getReg());
108       const TargetRegisterClass *SrcRC = MRI.getRegClass(Src.getReg());
109 
110       if (DstRC == &AMDGPU::VReg_1RegClass &&
111           TRI->getCommonSubClass(SrcRC, &AMDGPU::SGPR_64RegClass)) {
112         I1Defs.push_back(Dst.getReg());
113         DebugLoc DL = MI.getDebugLoc();
114 
115         MachineInstr *DefInst = MRI.getUniqueVRegDef(Src.getReg());
116         if (DefInst->getOpcode() == AMDGPU::S_MOV_B64) {
117           if (DefInst->getOperand(1).isImm()) {
118             I1Defs.push_back(Dst.getReg());
119 
120             int64_t Val = DefInst->getOperand(1).getImm();
121             assert(Val == 0 || Val == -1);
122 
123             BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_MOV_B32_e32))
124               .addOperand(Dst)
125               .addImm(Val);
126             MI.eraseFromParent();
127             continue;
128           }
129         }
130 
131         BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CNDMASK_B32_e64))
132           .addOperand(Dst)
133           .addImm(0)
134           .addImm(-1)
135           .addOperand(Src);
136         MI.eraseFromParent();
137       } else if (TRI->getCommonSubClass(DstRC, &AMDGPU::SGPR_64RegClass) &&
138                  SrcRC == &AMDGPU::VReg_1RegClass) {
139         BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(AMDGPU::V_CMP_NE_I32_e64))
140           .addOperand(Dst)
141           .addOperand(Src)
142           .addImm(0);
143         MI.eraseFromParent();
144       }
145     }
146   }
147 
148   for (unsigned Reg : I1Defs)
149     MRI.setRegClass(Reg, &AMDGPU::VGPR_32RegClass);
150 
151   return false;
152 }
153