lib/Target/ARM/MVEVPTBlockPass.cpp

   1 //===-- MVEVPTBlockPass.cpp - Insert MVE VPT blocks -----------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "ARM.h"
  10 #include "ARMMachineFunctionInfo.h"
  11 #include "ARMSubtarget.h"
  12 #include "MCTargetDesc/ARMBaseInfo.h"
  13 #include "Thumb2InstrInfo.h"
  14 #include "llvm/ADT/SmallSet.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/ADT/Statistic.h"
  17 #include "llvm/ADT/StringRef.h"
  18 #include "llvm/CodeGen/MachineBasicBlock.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineFunctionPass.h"
  21 #include "llvm/CodeGen/MachineInstr.h"
  22 #include "llvm/CodeGen/MachineInstrBuilder.h"
  23 #include "llvm/CodeGen/MachineInstrBundle.h"
  24 #include "llvm/CodeGen/MachineOperand.h"
  25 #include "llvm/IR/DebugLoc.h"
  26 #include "llvm/MC/MCInstrDesc.h"
  27 #include "llvm/MC/MCRegisterInfo.h"
  28 #include <cassert>
  29 #include <new>
  30
  31 using namespace llvm;
  32
  33 #define DEBUG_TYPE "arm-mve-vpt"
  34
  35 namespace {
  36   class MVEVPTBlock : public MachineFunctionPass {
  37   public:
  38     static char ID;
  39     const Thumb2InstrInfo *TII;
  40     const TargetRegisterInfo *TRI;
  41
  42     MVEVPTBlock() : MachineFunctionPass(ID) {}
  43
  44     bool runOnMachineFunction(MachineFunction &Fn) override;
  45
  46     MachineFunctionProperties getRequiredProperties() const override {
  47       return MachineFunctionProperties().set(
  48           MachineFunctionProperties::Property::NoVRegs);
  49     }
  50
  51     StringRef getPassName() const override {
  52       return "MVE VPT block insertion pass";
  53     }
  54
  55   private:
  56     bool InsertVPTBlocks(MachineBasicBlock &MBB);
  57   };
  58
  59   char MVEVPTBlock::ID = 0;
  60
  61 } // end anonymous namespace
  62
  63 INITIALIZE_PASS(MVEVPTBlock, DEBUG_TYPE, "ARM MVE VPT block pass", false, false)
  64
  65 enum VPTMaskValue {
  66   T     =  8, // 0b1000
  67   TT    =  4, // 0b0100
  68   TE    = 12, // 0b1100
  69   TTT   =  2, // 0b0010
  70   TTE   =  6, // 0b0110
  71   TEE   = 10, // 0b1010
  72   TET   = 14, // 0b1110
  73   TTTT  =  1, // 0b0001
  74   TTTE  =  3, // 0b0011
  75   TTEE  =  5, // 0b0101
  76   TTET  =  7, // 0b0111
  77   TEEE  =  9, // 0b1001
  78   TEET  = 11, // 0b1011
  79   TETT  = 13, // 0b1101
  80   TETE  = 15  // 0b1111
  81 };
  82
  83 bool MVEVPTBlock::InsertVPTBlocks(MachineBasicBlock &Block) {
  84   bool Modified = false;
  85   MachineBasicBlock::instr_iterator MBIter = Block.instr_begin();
  86   MachineBasicBlock::instr_iterator EndIter = Block.instr_end();
  87
  88   while (MBIter != EndIter) {
  89     MachineInstr *MI = &*MBIter;
  90     unsigned PredReg = 0;
  91     DebugLoc dl = MI->getDebugLoc();
  92
  93     ARMVCC::VPTCodes Pred = getVPTInstrPredicate(*MI, PredReg);
  94
  95     // The idea of the predicate is that None, Then and Else are for use when
  96     // handling assembly language: they correspond to the three possible
  97     // suffixes "", "t" and "e" on the mnemonic. So when instructions are read
  98     // from assembly source or disassembled from object code, you expect to see
  99     // a mixture whenever there's a long VPT block. But in code generation, we
 100     // hope we'll never generate an Else as input to this pass.
 101     assert(Pred != ARMVCC::Else && "VPT block pass does not expect Else preds");
 102
 103     if (Pred == ARMVCC::None) {
 104       ++MBIter;
 105       continue;
 106     }
 107
 108     LLVM_DEBUG(dbgs() << "VPT block created for: "; MI->dump());
 109     int VPTInstCnt = 1;
 110     ARMVCC::VPTCodes NextPred;
 111
 112     // Look at subsequent instructions, checking if they can be in the same VPT
 113     // block.
 114     ++MBIter;
 115     while (MBIter != EndIter && VPTInstCnt < 4) {
 116       NextPred = getVPTInstrPredicate(*MBIter, PredReg);
 117       assert(NextPred != ARMVCC::Else &&
 118              "VPT block pass does not expect Else preds");
 119       if (NextPred != Pred)
 120         break;
 121       LLVM_DEBUG(dbgs() << "  adding : "; MBIter->dump());
 122       ++VPTInstCnt;
 123       ++MBIter;
 124     };
 125
 126     // Create the new VPST
 127     MachineInstrBuilder MIBuilder =
 128         BuildMI(Block, MI, dl, TII->get(ARM::MVE_VPST));
 129     switch (VPTInstCnt) {
 130     case 1:
 131       MIBuilder.addImm(VPTMaskValue::T);
 132       break;
 133     case 2:
 134       MIBuilder.addImm(VPTMaskValue::TT);
 135       break;
 136     case 3:
 137       MIBuilder.addImm(VPTMaskValue::TTT);
 138       break;
 139     case 4:
 140       MIBuilder.addImm(VPTMaskValue::TTTT);
 141       break;
 142     default:
 143       llvm_unreachable("Unexpected number of instruction in a VPT block");
 144     };
 145
 146     finalizeBundle(
 147         Block, MachineBasicBlock::instr_iterator(MIBuilder.getInstr()), MBIter);
 148
 149     Modified = true;
 150   }
 151   return Modified;
 152 }
 153
 154 bool MVEVPTBlock::runOnMachineFunction(MachineFunction &Fn) {
 155   const ARMSubtarget &STI =
 156       static_cast<const ARMSubtarget &>(Fn.getSubtarget());
 157
 158   if (!STI.isThumb2() || !STI.hasMVEIntegerOps())
 159     return false;
 160
 161   TII = static_cast<const Thumb2InstrInfo *>(STI.getInstrInfo());
 162   TRI = STI.getRegisterInfo();
 163
 164   LLVM_DEBUG(dbgs() << "********** ARM MVE VPT BLOCKS **********\n"
 165                     << "********** Function: " << Fn.getName() << '\n');
 166
 167   bool Modified = false;
 168   for (MachineBasicBlock &MBB : Fn)
 169     Modified |= InsertVPTBlocks(MBB);
 170
 171   LLVM_DEBUG(dbgs() << "**************************************\n");
 172   return Modified;
 173 }
 174
 175 /// createMVEVPTBlock - Returns an instance of the MVE VPT block
 176 /// insertion pass.
 177 FunctionPass *llvm::createMVEVPTBlockPass() { return new MVEVPTBlock(); }