LLVM 20.0.0git
ARMBasicBlockInfo.h
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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"
19#include <algorithm>
20#include <cstdint>
21
22namespace llvm {
23
24struct 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.
33inline 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.
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.
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.
78 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
110
111private:
112 MachineFunction &MF;
113 bool isThumb = false;
114 const ARMBaseInstrInfo *TII = nullptr;
116
117public:
119 TII =
120 static_cast<const ARMBaseInstrInfo*>(MF.getSubtarget().getInstrInfo());
121 isThumb = MF.getInfo<ARMFunctionInfo>()->isThumbFunction();
122 }
123
125 BBInfo.resize(MF.getNumBlockIDs());
126 for (MachineBasicBlock &MBB : MF)
128 }
129
131
132 unsigned getOffsetOf(MachineInstr *MI) const;
133
135 return BBInfo[MBB->getNumber()].Offset;
136 }
137
139
141 BBInfo[MBB->getNumber()].Size += Size;
142 }
143
145 unsigned MaxDisp) const;
146
147 void insert(unsigned BBNum, BasicBlockInfo BBI) {
148 BBInfo.insert(BBInfo.begin() + BBNum, BBI);
149 }
150
151 void clear() { BBInfo.clear(); }
152
153 BBInfoVector &getBBInfo() { return BBInfo; }
154
155};
156
157} // end namespace llvm
158
159#endif // LLVM_LIB_TARGET_ARM_ARMBASICBLOCKINFO_H
MachineBasicBlock & MBB
uint64_t Size
const HexagonInstrInfo * TII
IRTranslator LLVM IR MI
static bool isThumbFunction(Function *F, Triple::ArchType ModuleArch)
bool isBBInRange(MachineInstr *MI, MachineBasicBlock *DestBB, unsigned MaxDisp) const
isBBInRange - Returns true if the distance between specific MI and specific BB can fit in MI's displa...
ARMBasicBlockUtils(MachineFunction &MF)
void insert(unsigned BBNum, BasicBlockInfo BBI)
void adjustBBOffsetsAfter(MachineBasicBlock *MBB)
void computeBlockSize(MachineBasicBlock *MBB)
unsigned getOffsetOf(MachineBasicBlock *MBB) const
unsigned getOffsetOf(MachineInstr *MI) const
getOffsetOf - Return the current offset of the specified machine instruction from the start of the fu...
void adjustBBSize(MachineBasicBlock *MBB, int Size)
ARMFunctionInfo - This class is derived from MachineFunctionInfo and contains private ARM-specific in...
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
unsigned getNumBlockIDs() const
getNumBlockIDs - Return the number of MBB ID's allocated.
Ty * getInfo()
getInfo - Keep track of various per-function pieces of information for backends that would like to do...
Representation of each machine instruction.
Definition: MachineInstr.h:69
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: SmallVector.h:586
iterator insert(iterator I, T &&Elt)
Definition: SmallVector.h:818
void resize(size_type N)
Definition: SmallVector.h:651
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
virtual const TargetInstrInfo * getInstrInfo() const
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
int countr_zero(T Val)
Count number of 0's from the least significant bit to the most stopping at the first 1.
Definition: bit.h:215
unsigned UnknownPadding(Align Alignment, unsigned KnownBits)
UnknownPadding - Return the worst case padding that could result from unknown offset bits.
unsigned Log2(Align A)
Returns the log2 of the alignment.
Definition: Alignment.h:208
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
uint64_t value() const
This is a hole in the type system and should not be abused.
Definition: Alignment.h:85
BasicBlockInfo - Information about the offset and size of a single basic block.
unsigned Size
Size - Size of the basic block in bytes.
Align PostAlign
PostAlign - When > 1, the block terminator contains a .align directive, so the end of the block is al...
uint8_t KnownBits
KnownBits - The number of low bits in Offset that are known to be exact.
unsigned internalKnownBits() const
Compute the number of known offset bits internally to this block.
BasicBlockInfo()=default
unsigned postOffset(Align Alignment=Align(1)) const
Compute the offset immediately following this block.
unsigned postKnownBits(Align Align=llvm::Align(1)) const
Compute the number of known low bits of postOffset.
uint8_t Unalign
Unalign - When non-zero, the block contains instructions (inline asm) of unknown size.
unsigned Offset
Offset - Distance from the beginning of the function to the beginning of this basic block.