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llvm-6502/lib/Target/Hexagon/HexagonNewValueJump.cpp
Eric Christopher 6035518e3b Have MachineFunction cache a pointer to the subtarget to make lookups 
shorter/easier and have the DAG use that to do the same lookup. This
can be used in the future for TargetMachine based caching lookups from
the MachineFunction easily.

Update the MIPS subtarget switching machinery to update this pointer
at the same time it runs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214838 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-05 02:39:49 +00:00

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//===----- HexagonNewValueJump.cpp - Hexagon Backend New Value Jump -------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements NewValueJump pass in Hexagon.
// Ideally, we should merge this as a Peephole pass prior to register
// allocation, but because we have a spill in between the feeder and new value
// jump instructions, we are forced to write after register allocation.
// Having said that, we should re-attempt to pull this earlier at some point
// in future.
// The basic approach looks for sequence of predicated jump, compare instruciton
// that genereates the predicate and, the feeder to the predicate. Once it finds
// all, it collapses compare and jump instruction into a new valu jump
// intstructions.
//
//
//===----------------------------------------------------------------------===//
#include "llvm/PassSupport.h"
#include "Hexagon.h"
#include "HexagonInstrInfo.h"
#include "HexagonMachineFunctionInfo.h"
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "HexagonTargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFunctionAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include <map>
using namespace llvm;
#define DEBUG_TYPE "hexagon-nvj"
STATISTIC(NumNVJGenerated, "Number of New Value Jump Instructions created");
static cl::opt<int>
DbgNVJCount("nvj-count", cl::init(-1), cl::Hidden, cl::desc(
"Maximum number of predicated jumps to be converted to New Value Jump"));
static cl::opt<bool> DisableNewValueJumps("disable-nvjump", cl::Hidden,
cl::ZeroOrMore, cl::init(false),
cl::desc("Disable New Value Jumps"));
namespace llvm {
void initializeHexagonNewValueJumpPass(PassRegistry&);
}
namespace {
struct HexagonNewValueJump : public MachineFunctionPass {
const HexagonInstrInfo *QII;
const HexagonRegisterInfo *QRI;
public:
static char ID;
HexagonNewValueJump() : MachineFunctionPass(ID) {
initializeHexagonNewValueJumpPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<MachineBranchProbabilityInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
const char *getPassName() const override {
return "Hexagon NewValueJump";
}
bool runOnMachineFunction(MachineFunction &Fn) override;
private:
/// \brief A handle to the branch probability pass.
const MachineBranchProbabilityInfo *MBPI;
};
} // end of anonymous namespace
char HexagonNewValueJump::ID = 0;
INITIALIZE_PASS_BEGIN(HexagonNewValueJump, "hexagon-nvj",
"Hexagon NewValueJump", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
INITIALIZE_PASS_END(HexagonNewValueJump, "hexagon-nvj",
"Hexagon NewValueJump", false, false)
// We have identified this II could be feeder to NVJ,
// verify that it can be.
static bool canBeFeederToNewValueJump(const HexagonInstrInfo *QII,
const TargetRegisterInfo *TRI,
MachineBasicBlock::iterator II,
MachineBasicBlock::iterator end,
MachineBasicBlock::iterator skip,
MachineFunction &MF) {
// Predicated instruction can not be feeder to NVJ.
if (QII->isPredicated(II))
return false;
// Bail out if feederReg is a paired register (double regs in
// our case). One would think that we can check to see if a given
// register cmpReg1 or cmpReg2 is a sub register of feederReg
// using -- if (QRI->isSubRegister(feederReg, cmpReg1) logic
// before the callsite of this function
// But we can not as it comes in the following fashion.
// %D0<def> = Hexagon_S2_lsr_r_p %D0<kill>, %R2<kill>
// %R0<def> = KILL %R0, %D0<imp-use,kill>
// %P0<def> = CMPEQri %R0<kill>, 0
// Hence, we need to check if it's a KILL instruction.
if (II->getOpcode() == TargetOpcode::KILL)
return false;
// Make sure there there is no 'def' or 'use' of any of the uses of
// feeder insn between it's definition, this MI and jump, jmpInst
// skipping compare, cmpInst.
// Here's the example.
// r21=memub(r22+r24<<#0)
// p0 = cmp.eq(r21, #0)
// r4=memub(r3+r21<<#0)
// if (p0.new) jump:t .LBB29_45
// Without this check, it will be converted into
// r4=memub(r3+r21<<#0)
// r21=memub(r22+r24<<#0)
// p0 = cmp.eq(r21, #0)
// if (p0.new) jump:t .LBB29_45
// and result WAR hazards if converted to New Value Jump.
for (unsigned i = 0; i < II->getNumOperands(); ++i) {
if (II->getOperand(i).isReg() &&
(II->getOperand(i).isUse() || II->getOperand(i).isDef())) {
MachineBasicBlock::iterator localII = II;
++localII;
unsigned Reg = II->getOperand(i).getReg();
for (MachineBasicBlock::iterator localBegin = localII;
localBegin != end; ++localBegin) {
if (localBegin == skip ) continue;
// Check for Subregisters too.
if (localBegin->modifiesRegister(Reg, TRI) ||
localBegin->readsRegister(Reg, TRI))
return false;
}
}
}
return true;
}
// These are the common checks that need to performed
// to determine if
// 1. compare instruction can be moved before jump.
// 2. feeder to the compare instruction can be moved before jump.
static bool commonChecksToProhibitNewValueJump(bool afterRA,
MachineBasicBlock::iterator MII) {
// If store in path, bail out.
if (MII->getDesc().mayStore())
return false;
// if call in path, bail out.
if (MII->getOpcode() == Hexagon::CALLv3)
return false;
// if NVJ is running prior to RA, do the following checks.
if (!afterRA) {
// The following Target Opcode instructions are spurious
// to new value jump. If they are in the path, bail out.
// KILL sets kill flag on the opcode. It also sets up a
// single register, out of pair.
// %D0<def> = Hexagon_S2_lsr_r_p %D0<kill>, %R2<kill>
// %R0<def> = KILL %R0, %D0<imp-use,kill>
// %P0<def> = CMPEQri %R0<kill>, 0
// PHI can be anything after RA.
// COPY can remateriaze things in between feeder, compare and nvj.
if (MII->getOpcode() == TargetOpcode::KILL ||
MII->getOpcode() == TargetOpcode::PHI ||
MII->getOpcode() == TargetOpcode::COPY)
return false;
// The following pseudo Hexagon instructions sets "use" and "def"
// of registers by individual passes in the backend. At this time,
// we don't know the scope of usage and definitions of these
// instructions.
if (MII->getOpcode() == Hexagon::TFR_condset_rr ||
MII->getOpcode() == Hexagon::TFR_condset_ii ||
MII->getOpcode() == Hexagon::TFR_condset_ri ||
MII->getOpcode() == Hexagon::TFR_condset_ir ||
MII->getOpcode() == Hexagon::LDriw_pred ||
MII->getOpcode() == Hexagon::STriw_pred)
return false;
}
return true;
}
static bool canCompareBeNewValueJump(const HexagonInstrInfo *QII,
const TargetRegisterInfo *TRI,
MachineBasicBlock::iterator II,
unsigned pReg,
bool secondReg,
bool optLocation,
MachineBasicBlock::iterator end,
MachineFunction &MF) {
MachineInstr *MI = II;
// If the second operand of the compare is an imm, make sure it's in the
// range specified by the arch.
if (!secondReg) {
int64_t v = MI->getOperand(2).getImm();
if (!(isUInt<5>(v) ||
((MI->getOpcode() == Hexagon::CMPEQri ||
MI->getOpcode() == Hexagon::CMPGTri) &&
(v == -1))))
return false;
}
unsigned cmpReg1, cmpOp2 = 0; // cmpOp2 assignment silences compiler warning.
cmpReg1 = MI->getOperand(1).getReg();
if (secondReg) {
cmpOp2 = MI->getOperand(2).getReg();
// Make sure that that second register is not from COPY
// At machine code level, we don't need this, but if we decide
// to move new value jump prior to RA, we would be needing this.
MachineRegisterInfo &MRI = MF.getRegInfo();
if (secondReg && !TargetRegisterInfo::isPhysicalRegister(cmpOp2)) {
MachineInstr *def = MRI.getVRegDef(cmpOp2);
if (def->getOpcode() == TargetOpcode::COPY)
return false;
}
}
// Walk the instructions after the compare (predicate def) to the jump,
// and satisfy the following conditions.
++II ;
for (MachineBasicBlock::iterator localII = II; localII != end;
++localII) {
// Check 1.
// If "common" checks fail, bail out.
if (!commonChecksToProhibitNewValueJump(optLocation, localII))
return false;
// Check 2.
// If there is a def or use of predicate (result of compare), bail out.
if (localII->modifiesRegister(pReg, TRI) ||
localII->readsRegister(pReg, TRI))
return false;
// Check 3.
// If there is a def of any of the use of the compare (operands of compare),
// bail out.
// Eg.
// p0 = cmp.eq(r2, r0)
// r2 = r4
// if (p0.new) jump:t .LBB28_3
if (localII->modifiesRegister(cmpReg1, TRI) ||
(secondReg && localII->modifiesRegister(cmpOp2, TRI)))
return false;
}
return true;
}
// Given a compare operator, return a matching New Value Jump
// compare operator. Make sure that MI here is included in
// HexagonInstrInfo.cpp::isNewValueJumpCandidate
static unsigned getNewValueJumpOpcode(MachineInstr *MI, int reg,
bool secondRegNewified,
MachineBasicBlock *jmpTarget,
const MachineBranchProbabilityInfo
*MBPI) {
bool taken = false;
MachineBasicBlock *Src = MI->getParent();
const BranchProbability Prediction =
MBPI->getEdgeProbability(Src, jmpTarget);
if (Prediction >= BranchProbability(1,2))
taken = true;
switch (MI->getOpcode()) {
case Hexagon::CMPEQrr:
return taken ? Hexagon::CMPEQrr_t_Jumpnv_t_V4
: Hexagon::CMPEQrr_t_Jumpnv_nt_V4;
case Hexagon::CMPEQri: {
if (reg >= 0)
return taken ? Hexagon::CMPEQri_t_Jumpnv_t_V4
: Hexagon::CMPEQri_t_Jumpnv_nt_V4;
else
return taken ? Hexagon::CMPEQn1_t_Jumpnv_t_V4
: Hexagon::CMPEQn1_t_Jumpnv_nt_V4;
}
case Hexagon::CMPGTrr: {
if (secondRegNewified)
return taken ? Hexagon::CMPLTrr_t_Jumpnv_t_V4
: Hexagon::CMPLTrr_t_Jumpnv_nt_V4;
else
return taken ? Hexagon::CMPGTrr_t_Jumpnv_t_V4
: Hexagon::CMPGTrr_t_Jumpnv_nt_V4;
}
case Hexagon::CMPGTri: {
if (reg >= 0)
return taken ? Hexagon::CMPGTri_t_Jumpnv_t_V4
: Hexagon::CMPGTri_t_Jumpnv_nt_V4;
else
return taken ? Hexagon::CMPGTn1_t_Jumpnv_t_V4
: Hexagon::CMPGTn1_t_Jumpnv_nt_V4;
}
case Hexagon::CMPGTUrr: {
if (secondRegNewified)
return taken ? Hexagon::CMPLTUrr_t_Jumpnv_t_V4
: Hexagon::CMPLTUrr_t_Jumpnv_nt_V4;
else
return taken ? Hexagon::CMPGTUrr_t_Jumpnv_t_V4
: Hexagon::CMPGTUrr_t_Jumpnv_nt_V4;
}
case Hexagon::CMPGTUri:
return taken ? Hexagon::CMPGTUri_t_Jumpnv_t_V4
: Hexagon::CMPGTUri_t_Jumpnv_nt_V4;
default:
llvm_unreachable("Could not find matching New Value Jump instruction.");
}
// return *some value* to avoid compiler warning
return 0;
}
bool HexagonNewValueJump::runOnMachineFunction(MachineFunction &MF) {
DEBUG(dbgs() << "********** Hexagon New Value Jump **********\n"
<< "********** Function: "
<< MF.getName() << "\n");
#if 0
// for now disable this, if we move NewValueJump before register
// allocation we need this information.
LiveVariables &LVs = getAnalysis<LiveVariables>();
#endif
QII = static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo());
QRI = static_cast<const HexagonRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
if (!QRI->Subtarget.hasV4TOps() ||
DisableNewValueJumps) {
return false;
}
int nvjCount = DbgNVJCount;
int nvjGenerated = 0;
// Loop through all the bb's of the function
for (MachineFunction::iterator MBBb = MF.begin(), MBBe = MF.end();
MBBb != MBBe; ++MBBb) {
MachineBasicBlock* MBB = MBBb;
DEBUG(dbgs() << "** dumping bb ** "
<< MBB->getNumber() << "\n");
DEBUG(MBB->dump());
DEBUG(dbgs() << "\n" << "********** dumping instr bottom up **********\n");
bool foundJump = false;
bool foundCompare = false;
bool invertPredicate = false;
unsigned predReg = 0; // predicate reg of the jump.
unsigned cmpReg1 = 0;
int cmpOp2 = 0;
bool MO1IsKill = false;
bool MO2IsKill = false;
MachineBasicBlock::iterator jmpPos;
MachineBasicBlock::iterator cmpPos;
MachineInstr *cmpInstr = nullptr, *jmpInstr = nullptr;
MachineBasicBlock *jmpTarget = nullptr;
bool afterRA = false;
bool isSecondOpReg = false;
bool isSecondOpNewified = false;
// Traverse the basic block - bottom up
for (MachineBasicBlock::iterator MII = MBB->end(), E = MBB->begin();
MII != E;) {
MachineInstr *MI = --MII;
if (MI->isDebugValue()) {
continue;
}
if ((nvjCount == 0) || (nvjCount > -1 && nvjCount <= nvjGenerated))
break;
DEBUG(dbgs() << "Instr: "; MI->dump(); dbgs() << "\n");
if (!foundJump &&
(MI->getOpcode() == Hexagon::JMP_t ||
MI->getOpcode() == Hexagon::JMP_f ||
MI->getOpcode() == Hexagon::JMP_tnew_t ||
MI->getOpcode() == Hexagon::JMP_tnew_nt ||
MI->getOpcode() == Hexagon::JMP_fnew_t ||
MI->getOpcode() == Hexagon::JMP_fnew_nt)) {
// This is where you would insert your compare and
// instr that feeds compare
jmpPos = MII;
jmpInstr = MI;
predReg = MI->getOperand(0).getReg();
afterRA = TargetRegisterInfo::isPhysicalRegister(predReg);
// If ifconverter had not messed up with the kill flags of the
// operands, the following check on the kill flag would suffice.
// if(!jmpInstr->getOperand(0).isKill()) break;
// This predicate register is live out out of BB
// this would only work if we can actually use Live
// variable analysis on phy regs - but LLVM does not
// provide LV analysis on phys regs.
//if(LVs.isLiveOut(predReg, *MBB)) break;
// Get all the successors of this block - which will always
// be 2. Check if the predicate register is live in in those
// successor. If yes, we can not delete the predicate -
// I am doing this only because LLVM does not provide LiveOut
// at the BB level.
bool predLive = false;
for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
SIE = MBB->succ_end(); SI != SIE; ++SI) {
MachineBasicBlock* succMBB = *SI;
if (succMBB->isLiveIn(predReg)) {
predLive = true;
}
}
if (predLive)
break;
jmpTarget = MI->getOperand(1).getMBB();
foundJump = true;
if (MI->getOpcode() == Hexagon::JMP_f ||
MI->getOpcode() == Hexagon::JMP_fnew_t ||
MI->getOpcode() == Hexagon::JMP_fnew_nt) {
invertPredicate = true;
}
continue;
}
// No new value jump if there is a barrier. A barrier has to be in its
// own packet. A barrier has zero operands. We conservatively bail out
// here if we see any instruction with zero operands.
if (foundJump && MI->getNumOperands() == 0)
break;
if (foundJump &&
!foundCompare &&
MI->getOperand(0).isReg() &&
MI->getOperand(0).getReg() == predReg) {
// Not all compares can be new value compare. Arch Spec: 7.6.1.1
if (QII->isNewValueJumpCandidate(MI)) {
assert((MI->getDesc().isCompare()) &&
"Only compare instruction can be collapsed into New Value Jump");
isSecondOpReg = MI->getOperand(2).isReg();
if (!canCompareBeNewValueJump(QII, QRI, MII, predReg, isSecondOpReg,
afterRA, jmpPos, MF))
break;
cmpInstr = MI;
cmpPos = MII;
foundCompare = true;
// We need cmpReg1 and cmpOp2(imm or reg) while building
// new value jump instruction.
cmpReg1 = MI->getOperand(1).getReg();
if (MI->getOperand(1).isKill())
MO1IsKill = true;
if (isSecondOpReg) {
cmpOp2 = MI->getOperand(2).getReg();
if (MI->getOperand(2).isKill())
MO2IsKill = true;
} else
cmpOp2 = MI->getOperand(2).getImm();
continue;
}
}
if (foundCompare && foundJump) {
// If "common" checks fail, bail out on this BB.
if (!commonChecksToProhibitNewValueJump(afterRA, MII))
break;
bool foundFeeder = false;
MachineBasicBlock::iterator feederPos = MII;
if (MI->getOperand(0).isReg() &&
MI->getOperand(0).isDef() &&
(MI->getOperand(0).getReg() == cmpReg1 ||
(isSecondOpReg &&
MI->getOperand(0).getReg() == (unsigned) cmpOp2))) {
unsigned feederReg = MI->getOperand(0).getReg();
// First try to see if we can get the feeder from the first operand
// of the compare. If we can not, and if secondOpReg is true
// (second operand of the compare is also register), try that one.
// TODO: Try to come up with some heuristic to figure out which
// feeder would benefit.
if (feederReg == cmpReg1) {
if (!canBeFeederToNewValueJump(QII, QRI, MII, jmpPos, cmpPos, MF)) {
if (!isSecondOpReg)
break;
else
continue;
} else
foundFeeder = true;
}
if (!foundFeeder &&
isSecondOpReg &&
feederReg == (unsigned) cmpOp2)
if (!canBeFeederToNewValueJump(QII, QRI, MII, jmpPos, cmpPos, MF))
break;
if (isSecondOpReg) {
// In case of CMPLT, or CMPLTU, or EQ with the second register
// to newify, swap the operands.
if (cmpInstr->getOpcode() == Hexagon::CMPEQrr &&
feederReg == (unsigned) cmpOp2) {
unsigned tmp = cmpReg1;
bool tmpIsKill = MO1IsKill;
cmpReg1 = cmpOp2;
MO1IsKill = MO2IsKill;
cmpOp2 = tmp;
MO2IsKill = tmpIsKill;
}
// Now we have swapped the operands, all we need to check is,
// if the second operand (after swap) is the feeder.
// And if it is, make a note.
if (feederReg == (unsigned)cmpOp2)
isSecondOpNewified = true;
}
// Now that we are moving feeder close the jump,
// make sure we are respecting the kill values of
// the operands of the feeder.
bool updatedIsKill = false;
for (unsigned i = 0; i < MI->getNumOperands(); i++) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.isUse()) {
unsigned feederReg = MO.getReg();
for (MachineBasicBlock::iterator localII = feederPos,
end = jmpPos; localII != end; localII++) {
MachineInstr *localMI = localII;
for (unsigned j = 0; j < localMI->getNumOperands(); j++) {
MachineOperand &localMO = localMI->getOperand(j);
if (localMO.isReg() && localMO.isUse() &&
localMO.isKill() && feederReg == localMO.getReg()) {
// We found that there is kill of a use register
// Set up a kill flag on the register
localMO.setIsKill(false);
MO.setIsKill();
updatedIsKill = true;
break;
}
}
if (updatedIsKill) break;
}
}
if (updatedIsKill) break;
}
MBB->splice(jmpPos, MI->getParent(), MI);
MBB->splice(jmpPos, MI->getParent(), cmpInstr);
DebugLoc dl = MI->getDebugLoc();
MachineInstr *NewMI;
assert((QII->isNewValueJumpCandidate(cmpInstr)) &&
"This compare is not a New Value Jump candidate.");
unsigned opc = getNewValueJumpOpcode(cmpInstr, cmpOp2,
isSecondOpNewified,
jmpTarget, MBPI);
if (invertPredicate)
opc = QII->getInvertedPredicatedOpcode(opc);
if (isSecondOpReg)
NewMI = BuildMI(*MBB, jmpPos, dl,
QII->get(opc))
.addReg(cmpReg1, getKillRegState(MO1IsKill))
.addReg(cmpOp2, getKillRegState(MO2IsKill))
.addMBB(jmpTarget);
else if ((cmpInstr->getOpcode() == Hexagon::CMPEQri ||
cmpInstr->getOpcode() == Hexagon::CMPGTri) &&
cmpOp2 == -1 )
// Corresponding new-value compare jump instructions don't have the
// operand for -1 immediate value.
NewMI = BuildMI(*MBB, jmpPos, dl,
QII->get(opc))
.addReg(cmpReg1, getKillRegState(MO1IsKill))
.addMBB(jmpTarget);
else
NewMI = BuildMI(*MBB, jmpPos, dl,
QII->get(opc))
.addReg(cmpReg1, getKillRegState(MO1IsKill))
.addImm(cmpOp2)
.addMBB(jmpTarget);
assert(NewMI && "New Value Jump Instruction Not created!");
(void)NewMI;
if (cmpInstr->getOperand(0).isReg() &&
cmpInstr->getOperand(0).isKill())
cmpInstr->getOperand(0).setIsKill(false);
if (cmpInstr->getOperand(1).isReg() &&
cmpInstr->getOperand(1).isKill())
cmpInstr->getOperand(1).setIsKill(false);
cmpInstr->eraseFromParent();
jmpInstr->eraseFromParent();
++nvjGenerated;
++NumNVJGenerated;
break;
}
}
}
}
return true;
}
FunctionPass *llvm::createHexagonNewValueJump() {
return new HexagonNewValueJump();
}
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