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//===-- MVEVPTBlockPass.cpp - Insert MVE VPT blocks -----------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMBaseInfo.h"
#include "Thumb2InstrInfo.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.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/MachineInstrBundle.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include <cassert>
#include <new>
using namespace llvm;
#define DEBUG_TYPE "arm-mve-vpt"
namespace {
class MVEVPTBlock : public MachineFunctionPass {
public:
static char ID;
const Thumb2InstrInfo *TII;
const TargetRegisterInfo *TRI;
MVEVPTBlock() : MachineFunctionPass(ID) {}
bool runOnMachineFunction(MachineFunction &Fn) override;
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().set(
MachineFunctionProperties::Property::NoVRegs);
}
StringRef getPassName() const override {
return "MVE VPT block insertion pass";
}
private:
bool InsertVPTBlocks(MachineBasicBlock &MBB);
};
char MVEVPTBlock::ID = 0;
} // end anonymous namespace
INITIALIZE_PASS(MVEVPTBlock, DEBUG_TYPE, "ARM MVE VPT block pass", false, false)
enum VPTMaskValue {
T = 8, // 0b1000
TT = 4, // 0b0100
TE = 12, // 0b1100
TTT = 2, // 0b0010
TTE = 6, // 0b0110
TEE = 10, // 0b1010
TET = 14, // 0b1110
TTTT = 1, // 0b0001
TTTE = 3, // 0b0011
TTEE = 5, // 0b0101
TTET = 7, // 0b0111
TEEE = 9, // 0b1001
TEET = 11, // 0b1011
TETT = 13, // 0b1101
TETE = 15 // 0b1111
};
bool MVEVPTBlock::InsertVPTBlocks(MachineBasicBlock &Block) {
bool Modified = false;
MachineBasicBlock::instr_iterator MBIter = Block.instr_begin();
MachineBasicBlock::instr_iterator EndIter = Block.instr_end();
while (MBIter != EndIter) {
MachineInstr *MI = &*MBIter;
unsigned PredReg = 0;
DebugLoc dl = MI->getDebugLoc();
ARMVCC::VPTCodes Pred = getVPTInstrPredicate(*MI, PredReg);
// The idea of the predicate is that None, Then and Else are for use when
// handling assembly language: they correspond to the three possible
// suffixes "", "t" and "e" on the mnemonic. So when instructions are read
// from assembly source or disassembled from object code, you expect to see
// a mixture whenever there's a long VPT block. But in code generation, we
// hope we'll never generate an Else as input to this pass.
assert(Pred != ARMVCC::Else && "VPT block pass does not expect Else preds");
if (Pred == ARMVCC::None) {
++MBIter;
continue;
}
LLVM_DEBUG(dbgs() << "VPT block created for: "; MI->dump());
int VPTInstCnt = 1;
ARMVCC::VPTCodes NextPred;
// Look at subsequent instructions, checking if they can be in the same VPT
// block.
++MBIter;
while (MBIter != EndIter && VPTInstCnt < 4) {
NextPred = getVPTInstrPredicate(*MBIter, PredReg);
assert(NextPred != ARMVCC::Else &&
"VPT block pass does not expect Else preds");
if (NextPred != Pred)
break;
LLVM_DEBUG(dbgs() << " adding : "; MBIter->dump());
++VPTInstCnt;
++MBIter;
};
// Create the new VPST
MachineInstrBuilder MIBuilder =
BuildMI(Block, MI, dl, TII->get(ARM::MVE_VPST));
switch (VPTInstCnt) {
case 1:
MIBuilder.addImm(VPTMaskValue::T);
break;
case 2:
MIBuilder.addImm(VPTMaskValue::TT);
break;
case 3:
MIBuilder.addImm(VPTMaskValue::TTT);
break;
case 4:
MIBuilder.addImm(VPTMaskValue::TTTT);
break;
default:
llvm_unreachable("Unexpected number of instruction in a VPT block");
};
finalizeBundle(
Block, MachineBasicBlock::instr_iterator(MIBuilder.getInstr()), MBIter);
Modified = true;
}
return Modified;
}
bool MVEVPTBlock::runOnMachineFunction(MachineFunction &Fn) {
const ARMSubtarget &STI =
static_cast<const ARMSubtarget &>(Fn.getSubtarget());
if (!STI.isThumb2() || !STI.hasMVEIntegerOps())
return false;
TII = static_cast<const Thumb2InstrInfo *>(STI.getInstrInfo());
TRI = STI.getRegisterInfo();
LLVM_DEBUG(dbgs() << "********** ARM MVE VPT BLOCKS **********\n"
<< "********** Function: " << Fn.getName() << '\n');
bool Modified = false;
for (MachineBasicBlock &MBB : Fn)
Modified |= InsertVPTBlocks(MBB);
LLVM_DEBUG(dbgs() << "**************************************\n");
return Modified;
}
/// createMVEVPTBlock - Returns an instance of the MVE VPT block
/// insertion pass.
FunctionPass *llvm::createMVEVPTBlockPass() { return new MVEVPTBlock(); }
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