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1 //===--- ARMComputeBlockSize.cpp - Compute machine block sizes ------------===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //
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8 //===----------------------------------------------------------------------===//
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9
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10 #include "ARM.h"
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121
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11 #include "ARMBaseInstrInfo.h"
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120
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12 #include "ARMBasicBlockInfo.h"
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121
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13 #include "ARMMachineFunctionInfo.h"
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14 #include "llvm/CodeGen/MachineBasicBlock.h"
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15 #include "llvm/CodeGen/MachineFunction.h"
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16 #include "llvm/CodeGen/MachineInstr.h"
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134
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17 #include "llvm/CodeGen/TargetSubtargetInfo.h"
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121
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18 #include <vector>
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19
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120
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20 using namespace llvm;
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21
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22 namespace llvm {
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23
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24 // mayOptimizeThumb2Instruction - Returns true if optimizeThumb2Instructions
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25 // below may shrink MI.
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26 static bool
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27 mayOptimizeThumb2Instruction(const MachineInstr *MI) {
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28 switch(MI->getOpcode()) {
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29 // optimizeThumb2Instructions.
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30 case ARM::t2LEApcrel:
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31 case ARM::t2LDRpci:
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32 // optimizeThumb2Branches.
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33 case ARM::t2B:
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34 case ARM::t2Bcc:
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35 case ARM::tBcc:
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36 // optimizeThumb2JumpTables.
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37 case ARM::t2BR_JT:
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38 return true;
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39 }
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40 return false;
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41 }
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42
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43 void computeBlockSize(MachineFunction *MF, MachineBasicBlock *MBB,
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44 BasicBlockInfo &BBI) {
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45 const ARMBaseInstrInfo *TII =
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46 static_cast<const ARMBaseInstrInfo *>(MF->getSubtarget().getInstrInfo());
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47 bool isThumb = MF->getInfo<ARMFunctionInfo>()->isThumbFunction();
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48 BBI.Size = 0;
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49 BBI.Unalign = 0;
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50 BBI.PostAlign = 0;
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51
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52 for (MachineInstr &I : *MBB) {
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53 BBI.Size += TII->getInstSizeInBytes(I);
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54 // For inline asm, getInstSizeInBytes returns a conservative estimate.
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55 // The actual size may be smaller, but still a multiple of the instr size.
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56 if (I.isInlineAsm())
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57 BBI.Unalign = isThumb ? 1 : 2;
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58 // Also consider instructions that may be shrunk later.
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59 else if (isThumb && mayOptimizeThumb2Instruction(&I))
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60 BBI.Unalign = 1;
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61 }
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62
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63 // tBR_JTr contains a .align 2 directive.
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64 if (!MBB->empty() && MBB->back().getOpcode() == ARM::tBR_JTr) {
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65 BBI.PostAlign = 2;
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66 MBB->getParent()->ensureAlignment(2);
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67 }
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68 }
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69
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70 std::vector<BasicBlockInfo> computeAllBlockSizes(MachineFunction *MF) {
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71 std::vector<BasicBlockInfo> BBInfo;
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72 BBInfo.resize(MF->getNumBlockIDs());
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73
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74 for (MachineBasicBlock &MBB : *MF)
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75 computeBlockSize(MF, &MBB, BBInfo[MBB.getNumber()]);
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76
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77 return BBInfo;
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78 }
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79
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121
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80 } // end namespace llvm
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