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//===-- ARMHazardRecognizer.cpp - ARM postra hazard recognizer ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "ARMHazardRecognizer.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMSubtarget.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
static bool hasRAWHazard(MachineInstr *DefMI, MachineInstr *MI,
const TargetRegisterInfo &TRI) {
// FIXME: Detect integer instructions properly.
const TargetInstrDesc &TID = MI->getDesc();
unsigned Domain = TID.TSFlags & ARMII::DomainMask;
if (TID.mayStore())
return false;
unsigned Opcode = TID.getOpcode();
if (Opcode == ARM::VMOVRS || Opcode == ARM::VMOVRRD)
return false;
if ((Domain & ARMII::DomainVFP) || (Domain & ARMII::DomainNEON))
return MI->readsRegister(DefMI->getOperand(0).getReg(), &TRI);
return false;
}
ScheduleHazardRecognizer::HazardType
ARMHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
assert(Stalls == 0 && "ARM hazards don't support scoreboard lookahead");
MachineInstr *MI = SU->getInstr();
if (!MI->isDebugValue()) {
if (ITBlockSize && MI != ITBlockMIs[ITBlockSize-1])
return Hazard;
// Look for special VMLA / VMLS hazards. A VMUL / VADD / VSUB following
// a VMLA / VMLS will cause 4 cycle stall.
const TargetInstrDesc &TID = MI->getDesc();
if (LastMI && (TID.TSFlags & ARMII::DomainMask) != ARMII::DomainGeneral) {
MachineInstr *DefMI = LastMI;
const TargetInstrDesc &LastTID = LastMI->getDesc();
// Skip over one non-VFP / NEON instruction.
if (!LastTID.isBarrier() &&
(LastTID.TSFlags & ARMII::DomainMask) == ARMII::DomainGeneral) {
MachineBasicBlock::iterator I = LastMI;
if (I != LastMI->getParent()->begin()) {
I = llvm::prior(I);
DefMI = &*I;
}
}
if (TII.isFpMLxInstruction(DefMI->getOpcode()) &&
(TII.canCauseFpMLxStall(MI->getOpcode()) ||
hasRAWHazard(DefMI, MI, TRI))) {
// Try to schedule another instruction for the next 4 cycles.
if (FpMLxStalls == 0)
FpMLxStalls = 4;
return Hazard;
}
}
}
return ScoreboardHazardRecognizer::getHazardType(SU, Stalls);
}
void ARMHazardRecognizer::Reset() {
LastMI = 0;
FpMLxStalls = 0;
ITBlockSize = 0;
ScoreboardHazardRecognizer::Reset();
}
void ARMHazardRecognizer::EmitInstruction(SUnit *SU) {
MachineInstr *MI = SU->getInstr();
unsigned Opcode = MI->getOpcode();
if (ITBlockSize) {
--ITBlockSize;
} else if (Opcode == ARM::t2IT) {
unsigned Mask = MI->getOperand(1).getImm();
unsigned NumTZ = CountTrailingZeros_32(Mask);
assert(NumTZ <= 3 && "Invalid IT mask!");
ITBlockSize = 4 - NumTZ;
MachineBasicBlock::iterator I = MI;
for (unsigned i = 0; i < ITBlockSize; ++i) {
// Advance to the next instruction, skipping any dbg_value instructions.
do {
++I;
} while (I->isDebugValue());
ITBlockMIs[ITBlockSize-1-i] = &*I;
}
}
if (!MI->isDebugValue()) {
LastMI = MI;
FpMLxStalls = 0;
}
ScoreboardHazardRecognizer::EmitInstruction(SU);
}
void ARMHazardRecognizer::AdvanceCycle() {
if (FpMLxStalls && --FpMLxStalls == 0)
// Stalled for 4 cycles but still can't schedule any other instructions.
LastMI = 0;
ScoreboardHazardRecognizer::AdvanceCycle();
}
void ARMHazardRecognizer::RecedeCycle() {
llvm_unreachable("reverse ARM hazard checking unsupported");
}
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