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//===- HexagonVExtract.cpp ------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// This pass will replace multiple occurrences of V6_extractw from the same
// vector register with a combination of a vector store and scalar loads.
//===----------------------------------------------------------------------===//
#include "Hexagon.h"
#include "HexagonInstrInfo.h"
#include "HexagonMachineFunctionInfo.h"
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Pass.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include <map>
using namespace llvm;
static cl::opt<unsigned> VExtractThreshold(
"hexagon-vextract-threshold", cl::Hidden, cl::init(1),
cl::desc("Threshold for triggering vextract replacement"));
namespace llvm {
void initializeHexagonVExtractPass(PassRegistry& Registry);
FunctionPass *createHexagonVExtract();
}
namespace {
class HexagonVExtract : public MachineFunctionPass {
public:
static char ID;
HexagonVExtract() : MachineFunctionPass(ID) {}
StringRef getPassName() const override {
return "Hexagon optimize vextract";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
MachineFunctionPass::getAnalysisUsage(AU);
}
bool runOnMachineFunction(MachineFunction &MF) override;
private:
const HexagonSubtarget *HST = nullptr;
const HexagonInstrInfo *HII = nullptr;
unsigned genElemLoad(MachineInstr *ExtI, unsigned BaseR,
MachineRegisterInfo &MRI);
};
char HexagonVExtract::ID = 0;
}
INITIALIZE_PASS(HexagonVExtract, "hexagon-vextract",
"Hexagon optimize vextract", false, false)
unsigned HexagonVExtract::genElemLoad(MachineInstr *ExtI, unsigned BaseR,
MachineRegisterInfo &MRI) {
MachineBasicBlock &ExtB = *ExtI->getParent();
DebugLoc DL = ExtI->getDebugLoc();
Register ElemR = MRI.createVirtualRegister(&Hexagon::IntRegsRegClass);
Register ExtIdxR = ExtI->getOperand(2).getReg();
unsigned ExtIdxS = ExtI->getOperand(2).getSubReg();
// Simplified check for a compile-time constant value of ExtIdxR.
if (ExtIdxS == 0) {
MachineInstr *DI = MRI.getVRegDef(ExtIdxR);
if (DI->getOpcode() == Hexagon::A2_tfrsi) {
unsigned V = DI->getOperand(1).getImm();
V &= (HST->getVectorLength()-1) & -4u;
BuildMI(ExtB, ExtI, DL, HII->get(Hexagon::L2_loadri_io), ElemR)
.addReg(BaseR)
.addImm(V);
return ElemR;
}
}
Register IdxR = MRI.createVirtualRegister(&Hexagon::IntRegsRegClass);
BuildMI(ExtB, ExtI, DL, HII->get(Hexagon::A2_andir), IdxR)
.add(ExtI->getOperand(2))
.addImm(-4);
BuildMI(ExtB, ExtI, DL, HII->get(Hexagon::L4_loadri_rr), ElemR)
.addReg(BaseR)
.addReg(IdxR)
.addImm(0);
return ElemR;
}
bool HexagonVExtract::runOnMachineFunction(MachineFunction &MF) {
HST = &MF.getSubtarget<HexagonSubtarget>();
HII = HST->getInstrInfo();
const auto &HRI = *HST->getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
MachineFrameInfo &MFI = MF.getFrameInfo();
Register AR =
MF.getInfo<HexagonMachineFunctionInfo>()->getStackAlignBaseReg();
std::map<unsigned, SmallVector<MachineInstr *, 4>> VExtractMap;
bool Changed = false;
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : MBB) {
unsigned Opc = MI.getOpcode();
if (Opc != Hexagon::V6_extractw)
continue;
Register VecR = MI.getOperand(1).getReg();
VExtractMap[VecR].push_back(&MI);
}
}
auto EmitAddr = [&] (MachineBasicBlock &BB, MachineBasicBlock::iterator At,
DebugLoc dl, int FI, unsigned Offset) {
Register AddrR = MRI.createVirtualRegister(&Hexagon::IntRegsRegClass);
unsigned FiOpc = AR != 0 ? Hexagon::PS_fia : Hexagon::PS_fi;
auto MIB = BuildMI(BB, At, dl, HII->get(FiOpc), AddrR);
if (AR)
MIB.addReg(AR);
MIB.addFrameIndex(FI).addImm(Offset);
return AddrR;
};
MaybeAlign MaxAlign;
for (auto &P : VExtractMap) {
unsigned VecR = P.first;
if (P.second.size() <= VExtractThreshold)
continue;
const auto &VecRC = *MRI.getRegClass(VecR);
Align Alignment = HRI.getSpillAlign(VecRC);
MaxAlign = std::max(MaxAlign.valueOrOne(), Alignment);
// Make sure this is not a spill slot: spill slots cannot be aligned
// if there are variable-sized objects on the stack. They must be
// accessible via FP (which is not aligned), because SP is unknown,
// and AP may not be available at the location of the load/store.
int FI = MFI.CreateStackObject(HRI.getSpillSize(VecRC), Alignment,
/*isSpillSlot*/ false);
MachineInstr *DefI = MRI.getVRegDef(VecR);
MachineBasicBlock::iterator At = std::next(DefI->getIterator());
MachineBasicBlock &DefB = *DefI->getParent();
unsigned StoreOpc = VecRC.getID() == Hexagon::HvxVRRegClassID
? Hexagon::V6_vS32b_ai
: Hexagon::PS_vstorerw_ai;
Register AddrR = EmitAddr(DefB, At, DefI->getDebugLoc(), FI, 0);
BuildMI(DefB, At, DefI->getDebugLoc(), HII->get(StoreOpc))
.addReg(AddrR)
.addImm(0)
.addReg(VecR);
unsigned VecSize = HRI.getRegSizeInBits(VecRC) / 8;
for (MachineInstr *ExtI : P.second) {
assert(ExtI->getOpcode() == Hexagon::V6_extractw);
unsigned SR = ExtI->getOperand(1).getSubReg();
assert(ExtI->getOperand(1).getReg() == VecR);
MachineBasicBlock &ExtB = *ExtI->getParent();
DebugLoc DL = ExtI->getDebugLoc();
Register BaseR = EmitAddr(ExtB, ExtI, ExtI->getDebugLoc(), FI,
SR == 0 ? 0 : VecSize/2);
unsigned ElemR = genElemLoad(ExtI, BaseR, MRI);
Register ExtR = ExtI->getOperand(0).getReg();
MRI.replaceRegWith(ExtR, ElemR);
ExtB.erase(ExtI);
Changed = true;
}
}
if (AR && MaxAlign) {
// Update the required stack alignment.
MachineInstr *AlignaI = MRI.getVRegDef(AR);
assert(AlignaI->getOpcode() == Hexagon::PS_aligna);
MachineOperand &Op = AlignaI->getOperand(1);
if (*MaxAlign > Op.getImm())
Op.setImm(MaxAlign->value());
}
return Changed;
}
FunctionPass *llvm::createHexagonVExtract() {
return new HexagonVExtract();
}
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