1 //===-- ARMBasicBlockInfo.h - Basic Block Information -----------*- C++ -*-===//
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 // Utility functions and data structure for computing block size.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #ifndef LLVM_LIB_TARGET_ARM_ARMBASICBLOCKINFO_H
14 #define LLVM_LIB_TARGET_ARM_ARMBASICBLOCKINFO_H
15
16 #include "ARMBaseInstrInfo.h"
17 #include "ARMMachineFunctionInfo.h"
18 #include "llvm/Support/MathExtras.h"
19 #include <algorithm>
20 #include <cstdint>
21
22 namespace llvm {
23
24 struct BasicBlockInfo;
25 using BBInfoVector = SmallVectorImpl<BasicBlockInfo>;
26
27 /// UnknownPadding - Return the worst case padding that could result from
28 /// unknown offset bits. This does not include alignment padding caused by
29 /// known offset bits.
30 ///
31 /// @param Alignment alignment
32 /// @param KnownBits Number of known low offset bits.
UnknownPadding(Align Alignment,unsigned KnownBits)33 inline unsigned UnknownPadding(Align Alignment, unsigned KnownBits) {
34 if (KnownBits < Log2(Alignment))
35 return Alignment.value() - (1ull << KnownBits);
36 return 0;
37 }
38
39 /// BasicBlockInfo - Information about the offset and size of a single
40 /// basic block.
41 struct BasicBlockInfo {
42 /// Offset - Distance from the beginning of the function to the beginning
43 /// of this basic block.
44 ///
45 /// Offsets are computed assuming worst case padding before an aligned
46 /// block. This means that subtracting basic block offsets always gives a
47 /// conservative estimate of the real distance which may be smaller.
48 ///
49 /// Because worst case padding is used, the computed offset of an aligned
50 /// block may not actually be aligned.
51 unsigned Offset = 0;
52
53 /// Size - Size of the basic block in bytes. If the block contains
54 /// inline assembly, this is a worst case estimate.
55 ///
56 /// The size does not include any alignment padding whether from the
57 /// beginning of the block, or from an aligned jump table at the end.
58 unsigned Size = 0;
59
60 /// KnownBits - The number of low bits in Offset that are known to be
61 /// exact. The remaining bits of Offset are an upper bound.
62 uint8_t KnownBits = 0;
63
64 /// Unalign - When non-zero, the block contains instructions (inline asm)
65 /// of unknown size. The real size may be smaller than Size bytes by a
66 /// multiple of 1 << Unalign.
67 uint8_t Unalign = 0;
68
69 /// PostAlign - When > 1, the block terminator contains a .align
70 /// directive, so the end of the block is aligned to PostAlign bytes.
71 Align PostAlign;
72
73 BasicBlockInfo() = default;
74
75 /// Compute the number of known offset bits internally to this block.
76 /// This number should be used to predict worst case padding when
77 /// splitting the block.
internalKnownBitsBasicBlockInfo78 unsigned internalKnownBits() const {
79 unsigned Bits = Unalign ? Unalign : KnownBits;
80 // If the block size isn't a multiple of the known bits, assume the
81 // worst case padding.
82 if (Size & ((1u << Bits) - 1))
83 Bits = llvm::countr_zero(Size);
84 return Bits;
85 }
86
87 /// Compute the offset immediately following this block. If Align is
88 /// specified, return the offset the successor block will get if it has
89 /// this alignment.
90 unsigned postOffset(Align Alignment = Align(1)) const {
91 unsigned PO = Offset + Size;
92 const Align PA = std::max(PostAlign, Alignment);
93 if (PA == Align(1))
94 return PO;
95 // Add alignment padding from the terminator.
96 return PO + UnknownPadding(PA, internalKnownBits());
97 }
98
99 /// Compute the number of known low bits of postOffset. If this block
100 /// contains inline asm, the number of known bits drops to the
101 /// instruction alignment. An aligned terminator may increase the number
102 /// of know bits.
103 /// If LogAlign is given, also consider the alignment of the next block.
104 unsigned postKnownBits(Align Align = llvm::Align(1)) const {
105 return std::max(Log2(std::max(PostAlign, Align)), internalKnownBits());
106 }
107 };
108
109 class ARMBasicBlockUtils {
110
111 private:
112 MachineFunction &MF;
113 bool isThumb = false;
114 const ARMBaseInstrInfo *TII = nullptr;
115 SmallVector<BasicBlockInfo, 8> BBInfo;
116
117 public:
ARMBasicBlockUtils(MachineFunction & MF)118 ARMBasicBlockUtils(MachineFunction &MF) : MF(MF) {
119 TII =
120 static_cast<const ARMBaseInstrInfo*>(MF.getSubtarget().getInstrInfo());
121 isThumb = MF.getInfo<ARMFunctionInfo>()->isThumbFunction();
122 }
123
computeAllBlockSizes()124 void computeAllBlockSizes() {
125 BBInfo.resize(MF.getNumBlockIDs());
126 for (MachineBasicBlock &MBB : MF)
127 computeBlockSize(&MBB);
128 }
129
130 void computeBlockSize(MachineBasicBlock *MBB);
131
132 unsigned getOffsetOf(MachineInstr *MI) const;
133
getOffsetOf(MachineBasicBlock * MBB)134 unsigned getOffsetOf(MachineBasicBlock *MBB) const {
135 return BBInfo[MBB->getNumber()].Offset;
136 }
137
138 void adjustBBOffsetsAfter(MachineBasicBlock *MBB);
139
adjustBBSize(MachineBasicBlock * MBB,int Size)140 void adjustBBSize(MachineBasicBlock *MBB, int Size) {
141 BBInfo[MBB->getNumber()].Size += Size;
142 }
143
144 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *DestBB,
145 unsigned MaxDisp) const;
146
insert(unsigned BBNum,BasicBlockInfo BBI)147 void insert(unsigned BBNum, BasicBlockInfo BBI) {
148 BBInfo.insert(BBInfo.begin() + BBNum, BBI);
149 }
150
clear()151 void clear() { BBInfo.clear(); }
152
getBBInfo()153 BBInfoVector &getBBInfo() { return BBInfo; }
154
155 };
156
157 } // end namespace llvm
158
159 #endif // LLVM_LIB_TARGET_ARM_ARMBASICBLOCKINFO_H
160