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clang-p2996/llvm/lib/Target/AMDGPU/GCNDPPCombine.cpp
Valery Pykhtin 7fe97f8c7c [AMDGPU] Fix DPP combiner 
Differential revision: https://reviews.llvm.org/D55444

dpp move with uses and old reg initializer should be in the same BB.
bound_ctrl:0 is only considered when bank_mask and row_mask are fully enabled (0xF). Otherwise the old register value is checked for identity.
Added add, subrev, and, or instructions to the old folding function.
Kill flag is cleared for the src0 (DPP register) as it may be copied into more than one user.

The pass is still disabled by default.

llvm-svn: 353513
2019-02-08 11:59:48 +00:00

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//=======- GCNDPPCombine.cpp - optimization for DPP instructions ---==========//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// The pass combines V_MOV_B32_dpp instruction with its VALU uses as a DPP src0
// operand. If any of the use instruction cannot be combined with the mov the
// whole sequence is reverted.
//
// $old = ...
// $dpp_value = V_MOV_B32_dpp $old, $vgpr_to_be_read_from_other_lane,
// dpp_controls..., $row_mask, $bank_mask, $bound_ctrl
// $res = VALU $dpp_value [, src1]
//
// to
//
// $res = VALU_DPP $combined_old, $vgpr_to_be_read_from_other_lane, [src1,]
// dpp_controls..., $row_mask, $bank_mask, $combined_bound_ctrl
//
// Combining rules :
//
// if $row_mask and $bank_mask are fully enabled (0xF) and
// $bound_ctrl==DPP_BOUND_ZERO or $old==0
// -> $combined_old = undef,
// $combined_bound_ctrl = DPP_BOUND_ZERO
//
// if the VALU op is binary and
// $bound_ctrl==DPP_BOUND_OFF and
// $old==identity value (immediate) for the VALU op
// -> $combined_old = src1,
// $combined_bound_ctrl = DPP_BOUND_OFF
//
// Othervise cancel.
//
// The mov_dpp instruction should recide in the same BB as all it's uses
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "AMDGPUSubtarget.h"
#include "SIInstrInfo.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/Pass.h"
#include <cassert>
using namespace llvm;
#define DEBUG_TYPE "gcn-dpp-combine"
STATISTIC(NumDPPMovsCombined, "Number of DPP moves combined.");
namespace {
class GCNDPPCombine : public MachineFunctionPass {
MachineRegisterInfo *MRI;
const SIInstrInfo *TII;
using RegSubRegPair = TargetInstrInfo::RegSubRegPair;
MachineOperand *getOldOpndValue(MachineOperand &OldOpnd) const;
MachineInstr *createDPPInst(MachineInstr &OrigMI,
MachineInstr &MovMI,
RegSubRegPair CombOldVGPR,
MachineOperand *OldOpnd,
bool CombBCZ) const;
MachineInstr *createDPPInst(MachineInstr &OrigMI,
MachineInstr &MovMI,
RegSubRegPair CombOldVGPR,
bool CombBCZ) const;
bool hasNoImmOrEqual(MachineInstr &MI,
unsigned OpndName,
int64_t Value,
int64_t Mask = -1) const;
bool combineDPPMov(MachineInstr &MI) const;
public:
static char ID;
GCNDPPCombine() : MachineFunctionPass(ID) {
initializeGCNDPPCombinePass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
StringRef getPassName() const override { return "GCN DPP Combine"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
} // end anonymous namespace
INITIALIZE_PASS(GCNDPPCombine, DEBUG_TYPE, "GCN DPP Combine", false, false)
char GCNDPPCombine::ID = 0;
char &llvm::GCNDPPCombineID = GCNDPPCombine::ID;
FunctionPass *llvm::createGCNDPPCombinePass() {
return new GCNDPPCombine();
}
static int getDPPOp(unsigned Op) {
auto DPP32 = AMDGPU::getDPPOp32(Op);
if (DPP32 != -1)
return DPP32;
auto E32 = AMDGPU::getVOPe32(Op);
return E32 != -1 ? AMDGPU::getDPPOp32(E32) : -1;
}
// tracks the register operand definition and returns:
// 1. immediate operand used to initialize the register if found
// 2. nullptr if the register operand is undef
// 3. the operand itself otherwise
MachineOperand *GCNDPPCombine::getOldOpndValue(MachineOperand &OldOpnd) const {
auto *Def = getVRegSubRegDef(getRegSubRegPair(OldOpnd), *MRI);
if (!Def)
return nullptr;
switch(Def->getOpcode()) {
default: break;
case AMDGPU::IMPLICIT_DEF:
return nullptr;
case AMDGPU::COPY:
case AMDGPU::V_MOV_B32_e32: {
auto &Op1 = Def->getOperand(1);
if (Op1.isImm())
return &Op1;
break;
}
}
return &OldOpnd;
}
MachineInstr *GCNDPPCombine::createDPPInst(MachineInstr &OrigMI,
MachineInstr &MovMI,
RegSubRegPair CombOldVGPR,
bool CombBCZ) const {
assert(MovMI.getOpcode() == AMDGPU::V_MOV_B32_dpp);
assert(TII->getNamedOperand(MovMI, AMDGPU::OpName::vdst)->getReg() ==
TII->getNamedOperand(OrigMI, AMDGPU::OpName::src0)->getReg());
auto OrigOp = OrigMI.getOpcode();
auto DPPOp = getDPPOp(OrigOp);
if (DPPOp == -1) {
LLVM_DEBUG(dbgs() << " failed: no DPP opcode\n");
return nullptr;
}
auto DPPInst = BuildMI(*OrigMI.getParent(), OrigMI,
OrigMI.getDebugLoc(), TII->get(DPPOp));
bool Fail = false;
do {
auto *Dst = TII->getNamedOperand(OrigMI, AMDGPU::OpName::vdst);
assert(Dst);
DPPInst.add(*Dst);
int NumOperands = 1;
const int OldIdx = AMDGPU::getNamedOperandIdx(DPPOp, AMDGPU::OpName::old);
if (OldIdx != -1) {
assert(OldIdx == NumOperands);
assert(isOfRegClass(CombOldVGPR, AMDGPU::VGPR_32RegClass, *MRI));
DPPInst.addReg(CombOldVGPR.Reg, 0, CombOldVGPR.SubReg);
++NumOperands;
} else {
// TODO: this discards MAC/FMA instructions for now, let's add it later
LLVM_DEBUG(dbgs() << " failed: no old operand in DPP instruction,"
" TBD\n");
Fail = true;
break;
}
if (auto *Mod0 = TII->getNamedOperand(OrigMI,
AMDGPU::OpName::src0_modifiers)) {
assert(NumOperands == AMDGPU::getNamedOperandIdx(DPPOp,
AMDGPU::OpName::src0_modifiers));
assert(0LL == (Mod0->getImm() & ~(SISrcMods::ABS | SISrcMods::NEG)));
DPPInst.addImm(Mod0->getImm());
++NumOperands;
}
auto *Src0 = TII->getNamedOperand(MovMI, AMDGPU::OpName::src0);
assert(Src0);
if (!TII->isOperandLegal(*DPPInst.getInstr(), NumOperands, Src0)) {
LLVM_DEBUG(dbgs() << " failed: src0 is illegal\n");
Fail = true;
break;
}
DPPInst.add(*Src0);
DPPInst->getOperand(NumOperands).setIsKill(false);
++NumOperands;
if (auto *Mod1 = TII->getNamedOperand(OrigMI,
AMDGPU::OpName::src1_modifiers)) {
assert(NumOperands == AMDGPU::getNamedOperandIdx(DPPOp,
AMDGPU::OpName::src1_modifiers));
assert(0LL == (Mod1->getImm() & ~(SISrcMods::ABS | SISrcMods::NEG)));
DPPInst.addImm(Mod1->getImm());
++NumOperands;
}
if (auto *Src1 = TII->getNamedOperand(OrigMI, AMDGPU::OpName::src1)) {
if (!TII->isOperandLegal(*DPPInst.getInstr(), NumOperands, Src1)) {
LLVM_DEBUG(dbgs() << " failed: src1 is illegal\n");
Fail = true;
break;
}
DPPInst.add(*Src1);
++NumOperands;
}
if (auto *Src2 = TII->getNamedOperand(OrigMI, AMDGPU::OpName::src2)) {
if (!TII->isOperandLegal(*DPPInst.getInstr(), NumOperands, Src2)) {
LLVM_DEBUG(dbgs() << " failed: src2 is illegal\n");
Fail = true;
break;
}
DPPInst.add(*Src2);
}
DPPInst.add(*TII->getNamedOperand(MovMI, AMDGPU::OpName::dpp_ctrl));
DPPInst.add(*TII->getNamedOperand(MovMI, AMDGPU::OpName::row_mask));
DPPInst.add(*TII->getNamedOperand(MovMI, AMDGPU::OpName::bank_mask));
DPPInst.addImm(CombBCZ ? 1 : 0);
} while (false);
if (Fail) {
DPPInst.getInstr()->eraseFromParent();
return nullptr;
}
LLVM_DEBUG(dbgs() << " combined: " << *DPPInst.getInstr());
return DPPInst.getInstr();
}
static bool isIdentityValue(unsigned OrigMIOp, MachineOperand *OldOpnd) {
assert(OldOpnd->isImm());
switch (OrigMIOp) {
default: break;
case AMDGPU::V_ADD_U32_e32:
case AMDGPU::V_ADD_I32_e32:
case AMDGPU::V_OR_B32_e32:
case AMDGPU::V_SUBREV_U32_e32:
case AMDGPU::V_SUBREV_I32_e32:
case AMDGPU::V_MAX_U32_e32:
case AMDGPU::V_XOR_B32_e32:
if (OldOpnd->getImm() == 0)
return true;
break;
case AMDGPU::V_AND_B32_e32:
case AMDGPU::V_MIN_U32_e32:
if (static_cast<uint32_t>(OldOpnd->getImm()) ==
std::numeric_limits<uint32_t>::max())
return true;
break;
case AMDGPU::V_MIN_I32_e32:
if (static_cast<int32_t>(OldOpnd->getImm()) ==
std::numeric_limits<int32_t>::max())
return true;
break;
case AMDGPU::V_MAX_I32_e32:
if (static_cast<int32_t>(OldOpnd->getImm()) ==
std::numeric_limits<int32_t>::min())
return true;
break;
case AMDGPU::V_MUL_I32_I24_e32:
case AMDGPU::V_MUL_U32_U24_e32:
if (OldOpnd->getImm() == 1)
return true;
break;
}
return false;
}
MachineInstr *GCNDPPCombine::createDPPInst(MachineInstr &OrigMI,
MachineInstr &MovMI,
RegSubRegPair CombOldVGPR,
MachineOperand *OldOpndValue,
bool CombBCZ) const {
assert(CombOldVGPR.Reg);
if (!CombBCZ && OldOpndValue && OldOpndValue->isImm()) {
auto *Src1 = TII->getNamedOperand(OrigMI, AMDGPU::OpName::src1);
if (!Src1 || !Src1->isReg()) {
LLVM_DEBUG(dbgs() << " failed: no src1 or it isn't a register\n");
return nullptr;
}
if (!isIdentityValue(OrigMI.getOpcode(), OldOpndValue)) {
LLVM_DEBUG(dbgs() << " failed: old immediate ins't an identity\n");
return nullptr;
}
CombOldVGPR = getRegSubRegPair(*Src1);
if (!isOfRegClass(CombOldVGPR, AMDGPU::VGPR_32RegClass, *MRI)) {
LLVM_DEBUG(dbgs() << " failed: src1 isn't a VGPR32 register\n");
return nullptr;
}
}
return createDPPInst(OrigMI, MovMI, CombOldVGPR, CombBCZ);
}
// returns true if MI doesn't have OpndName immediate operand or the
// operand has Value
bool GCNDPPCombine::hasNoImmOrEqual(MachineInstr &MI, unsigned OpndName,
int64_t Value, int64_t Mask) const {
auto *Imm = TII->getNamedOperand(MI, OpndName);
if (!Imm)
return true;
assert(Imm->isImm());
return (Imm->getImm() & Mask) == Value;
}
bool GCNDPPCombine::combineDPPMov(MachineInstr &MovMI) const {
assert(MovMI.getOpcode() == AMDGPU::V_MOV_B32_dpp);
LLVM_DEBUG(dbgs() << "\nDPP combine: " << MovMI);
auto *DstOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::vdst);
assert(DstOpnd && DstOpnd->isReg());
auto DPPMovReg = DstOpnd->getReg();
if (!isEXECMaskConstantBetweenDefAndUses(DPPMovReg, *MRI)) {
LLVM_DEBUG(dbgs() << " failed: EXEC mask should remain the same"
" for all uses\n");
return false;
}
auto *RowMaskOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::row_mask);
assert(RowMaskOpnd && RowMaskOpnd->isImm());
auto *BankMaskOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::bank_mask);
assert(BankMaskOpnd && BankMaskOpnd->isImm());
const bool MaskAllLanes = RowMaskOpnd->getImm() == 0xF &&
BankMaskOpnd->getImm() == 0xF;
auto *BCZOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::bound_ctrl);
assert(BCZOpnd && BCZOpnd->isImm());
bool BoundCtrlZero = BCZOpnd->getImm();
auto *OldOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::old);
assert(OldOpnd && OldOpnd->isReg());
auto * const OldOpndValue = getOldOpndValue(*OldOpnd);
// OldOpndValue is either undef (IMPLICIT_DEF) or immediate or something else
// We could use: assert(!OldOpndValue || OldOpndValue->isImm())
// but the third option is used to distinguish undef from non-immediate
// to reuse IMPLICIT_DEF instruction later
assert(!OldOpndValue || OldOpndValue->isImm() || OldOpndValue == OldOpnd);
bool CombBCZ = false;
if (MaskAllLanes && BoundCtrlZero) { // [1]
CombBCZ = true;
} else {
if (!OldOpndValue || !OldOpndValue->isImm()) {
LLVM_DEBUG(dbgs() << " failed: the DPP mov isn't combinable\n");
return false;
}
if (OldOpndValue->getParent()->getParent() != MovMI.getParent()) {
LLVM_DEBUG(dbgs() <<
" failed: old reg def and mov should be in the same BB\n");
return false;
}
if (OldOpndValue->getImm() == 0) {
if (MaskAllLanes) {
assert(!BoundCtrlZero); // by check [1]
CombBCZ = true;
}
} else if (BoundCtrlZero) {
assert(!MaskAllLanes); // by check [1]
LLVM_DEBUG(dbgs() <<
" failed: old!=0 and bctrl:0 and not all lanes isn't combinable\n");
return false;
}
}
LLVM_DEBUG(dbgs() << " old=";
if (!OldOpndValue)
dbgs() << "undef";
else
dbgs() << *OldOpndValue;
dbgs() << ", bound_ctrl=" << CombBCZ << '\n');
SmallVector<MachineInstr*, 4> OrigMIs, DPPMIs;
auto CombOldVGPR = getRegSubRegPair(*OldOpnd);
// try to reuse previous old reg if its undefined (IMPLICIT_DEF)
if (CombBCZ && OldOpndValue) { // CombOldVGPR should be undef
CombOldVGPR = RegSubRegPair(
MRI->createVirtualRegister(&AMDGPU::VGPR_32RegClass));
auto UndefInst = BuildMI(*MovMI.getParent(), MovMI, MovMI.getDebugLoc(),
TII->get(AMDGPU::IMPLICIT_DEF), CombOldVGPR.Reg);
DPPMIs.push_back(UndefInst.getInstr());
}
OrigMIs.push_back(&MovMI);
bool Rollback = true;
for (auto &Use : MRI->use_nodbg_operands(DPPMovReg)) {
Rollback = true;
auto &OrigMI = *Use.getParent();
LLVM_DEBUG(dbgs() << " try: " << OrigMI);
auto OrigOp = OrigMI.getOpcode();
if (TII->isVOP3(OrigOp)) {
if (!TII->hasVALU32BitEncoding(OrigOp)) {
LLVM_DEBUG(dbgs() << " failed: VOP3 hasn't e32 equivalent\n");
break;
}
// check if other than abs|neg modifiers are set (opsel for example)
const int64_t Mask = ~(SISrcMods::ABS | SISrcMods::NEG);
if (!hasNoImmOrEqual(OrigMI, AMDGPU::OpName::src0_modifiers, 0, Mask) ||
!hasNoImmOrEqual(OrigMI, AMDGPU::OpName::src1_modifiers, 0, Mask) ||
!hasNoImmOrEqual(OrigMI, AMDGPU::OpName::clamp, 0) ||
!hasNoImmOrEqual(OrigMI, AMDGPU::OpName::omod, 0)) {
LLVM_DEBUG(dbgs() << " failed: VOP3 has non-default modifiers\n");
break;
}
} else if (!TII->isVOP1(OrigOp) && !TII->isVOP2(OrigOp)) {
LLVM_DEBUG(dbgs() << " failed: not VOP1/2/3\n");
break;
}
LLVM_DEBUG(dbgs() << " combining: " << OrigMI);
if (&Use == TII->getNamedOperand(OrigMI, AMDGPU::OpName::src0)) {
if (auto *DPPInst = createDPPInst(OrigMI, MovMI, CombOldVGPR,
OldOpndValue, CombBCZ)) {
DPPMIs.push_back(DPPInst);
Rollback = false;
}
} else if (OrigMI.isCommutable() &&
&Use == TII->getNamedOperand(OrigMI, AMDGPU::OpName::src1)) {
auto *BB = OrigMI.getParent();
auto *NewMI = BB->getParent()->CloneMachineInstr(&OrigMI);
BB->insert(OrigMI, NewMI);
if (TII->commuteInstruction(*NewMI)) {
LLVM_DEBUG(dbgs() << " commuted: " << *NewMI);
if (auto *DPPInst = createDPPInst(*NewMI, MovMI, CombOldVGPR,
OldOpndValue, CombBCZ)) {
DPPMIs.push_back(DPPInst);
Rollback = false;
}
} else
LLVM_DEBUG(dbgs() << " failed: cannot be commuted\n");
NewMI->eraseFromParent();
} else
LLVM_DEBUG(dbgs() << " failed: no suitable operands\n");
if (Rollback)
break;
OrigMIs.push_back(&OrigMI);
}
for (auto *MI : *(Rollback? &DPPMIs : &OrigMIs))
MI->eraseFromParent();
return !Rollback;
}
bool GCNDPPCombine::runOnMachineFunction(MachineFunction &MF) {
auto &ST = MF.getSubtarget<GCNSubtarget>();
if (!ST.hasDPP() || skipFunction(MF.getFunction()))
return false;
MRI = &MF.getRegInfo();
TII = ST.getInstrInfo();
assert(MRI->isSSA() && "Must be run on SSA");
bool Changed = false;
for (auto &MBB : MF) {
for (auto I = MBB.rbegin(), E = MBB.rend(); I != E;) {
auto &MI = *I++;
if (MI.getOpcode() == AMDGPU::V_MOV_B32_dpp && combineDPPMov(MI)) {
Changed = true;
++NumDPPMovsCombined;
}
}
}
return Changed;
}
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