1 //===-- ARMHazardRecognizer.cpp - ARM postra hazard recognizer ------------===//
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 #include "ARMHazardRecognizer.h"
11 #include "ARMBaseInstrInfo.h"
12 #include "ARMBaseRegisterInfo.h"
13 #include "ARMSubtarget.h"
14 #include "llvm/CodeGen/MachineInstr.h"
15 #include "llvm/CodeGen/ScheduleDAG.h"
16 #include "llvm/Target/TargetRegisterInfo.h"
17 using namespace llvm;
18
hasRAWHazard(MachineInstr * DefMI,MachineInstr * MI,const TargetRegisterInfo & TRI)19 static bool hasRAWHazard(MachineInstr *DefMI, MachineInstr *MI,
20 const TargetRegisterInfo &TRI) {
21 // FIXME: Detect integer instructions properly.
22 const MCInstrDesc &MCID = MI->getDesc();
23 unsigned Domain = MCID.TSFlags & ARMII::DomainMask;
24 if (MI->mayStore())
25 return false;
26 unsigned Opcode = MCID.getOpcode();
27 if (Opcode == ARM::VMOVRS || Opcode == ARM::VMOVRRD)
28 return false;
29 if ((Domain & ARMII::DomainVFP) || (Domain & ARMII::DomainNEON))
30 return MI->readsRegister(DefMI->getOperand(0).getReg(), &TRI);
31 return false;
32 }
33
34 ScheduleHazardRecognizer::HazardType
getHazardType(SUnit * SU,int Stalls)35 ARMHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
36 assert(Stalls == 0 && "ARM hazards don't support scoreboard lookahead");
37
38 MachineInstr *MI = SU->getInstr();
39
40 if (!MI->isDebugValue()) {
41 // Look for special VMLA / VMLS hazards. A VMUL / VADD / VSUB following
42 // a VMLA / VMLS will cause 4 cycle stall.
43 const MCInstrDesc &MCID = MI->getDesc();
44 if (LastMI && (MCID.TSFlags & ARMII::DomainMask) != ARMII::DomainGeneral) {
45 MachineInstr *DefMI = LastMI;
46 const MCInstrDesc &LastMCID = LastMI->getDesc();
47 const TargetMachine &TM =
48 MI->getParent()->getParent()->getTarget();
49 const ARMBaseInstrInfo &TII =
50 *static_cast<const ARMBaseInstrInfo*>(TM.getInstrInfo());
51
52 // Skip over one non-VFP / NEON instruction.
53 if (!LastMI->isBarrier() &&
54 // On A9, AGU and NEON/FPU are muxed.
55 !(TII.getSubtarget().isLikeA9() &&
56 (LastMI->mayLoad() || LastMI->mayStore())) &&
57 (LastMCID.TSFlags & ARMII::DomainMask) == ARMII::DomainGeneral) {
58 MachineBasicBlock::iterator I = LastMI;
59 if (I != LastMI->getParent()->begin()) {
60 I = std::prev(I);
61 DefMI = &*I;
62 }
63 }
64
65 if (TII.isFpMLxInstruction(DefMI->getOpcode()) &&
66 (TII.canCauseFpMLxStall(MI->getOpcode()) ||
67 hasRAWHazard(DefMI, MI, TII.getRegisterInfo()))) {
68 // Try to schedule another instruction for the next 4 cycles.
69 if (FpMLxStalls == 0)
70 FpMLxStalls = 4;
71 return Hazard;
72 }
73 }
74 }
75
76 return ScoreboardHazardRecognizer::getHazardType(SU, Stalls);
77 }
78
Reset()79 void ARMHazardRecognizer::Reset() {
80 LastMI = nullptr;
81 FpMLxStalls = 0;
82 ScoreboardHazardRecognizer::Reset();
83 }
84
EmitInstruction(SUnit * SU)85 void ARMHazardRecognizer::EmitInstruction(SUnit *SU) {
86 MachineInstr *MI = SU->getInstr();
87 if (!MI->isDebugValue()) {
88 LastMI = MI;
89 FpMLxStalls = 0;
90 }
91
92 ScoreboardHazardRecognizer::EmitInstruction(SU);
93 }
94
AdvanceCycle()95 void ARMHazardRecognizer::AdvanceCycle() {
96 if (FpMLxStalls && --FpMLxStalls == 0)
97 // Stalled for 4 cycles but still can't schedule any other instructions.
98 LastMI = nullptr;
99 ScoreboardHazardRecognizer::AdvanceCycle();
100 }
101
RecedeCycle()102 void ARMHazardRecognizer::RecedeCycle() {
103 llvm_unreachable("reverse ARM hazard checking unsupported");
104 }
105