1 //===- llvm/ADT/SmallVector.cpp - 'Normally small' vectors ----------------===//
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 // This file implements the SmallVector class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/ADT/SmallVector.h"
14 #include <cstdint>
15 using namespace llvm;
16 
17 // Check that no bytes are wasted and everything is well-aligned.
18 namespace {
19 struct Struct16B {
20   alignas(16) void *X;
21 };
22 struct Struct32B {
23   alignas(32) void *X;
24 };
25 }
26 static_assert(sizeof(SmallVector<void *, 0>) ==
27                   sizeof(unsigned) * 2 + sizeof(void *),
28               "wasted space in SmallVector size 0");
29 static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
30               "wrong alignment for 16-byte aligned T");
31 static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
32               "wrong alignment for 32-byte aligned T");
33 static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
34               "missing padding for 16-byte aligned T");
35 static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
36               "missing padding for 32-byte aligned T");
37 static_assert(sizeof(SmallVector<void *, 1>) ==
38                   sizeof(unsigned) * 2 + sizeof(void *) * 2,
39               "wasted space in SmallVector size 1");
40 
41 static_assert(sizeof(SmallVector<char, 0>) ==
42                   sizeof(void *) * 2 + sizeof(void *),
43               "1 byte elements have word-sized type for size and capacity");
44 
45 // Note: Moving this function into the header may cause performance regression.
46 template <class Size_T>
47 void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinCapacity,
48                                        size_t TSize) {
49   // Ensure we can fit the new capacity.
50   // This is only going to be applicable when the capacity is 32 bit.
51   if (MinCapacity > SizeTypeMax())
52     report_bad_alloc_error("SmallVector capacity overflow during allocation");
53 
54   // Ensure we can meet the guarantee of space for at least one more element.
55   // The above check alone will not catch the case where grow is called with a
56   // default MinCapacity of 0, but the current capacity cannot be increased.
57   // This is only going to be applicable when the capacity is 32 bit.
58   if (capacity() == SizeTypeMax())
59     report_bad_alloc_error("SmallVector capacity unable to grow");
60 
61   // In theory 2*capacity can overflow if the capacity is 64 bit, but the
62   // original capacity would never be large enough for this to be a problem.
63   size_t NewCapacity = 2 * capacity() + 1; // Always grow.
64   NewCapacity = std::min(std::max(NewCapacity, MinCapacity), SizeTypeMax());
65 
66   void *NewElts;
67   if (BeginX == FirstEl) {
68     NewElts = safe_malloc(NewCapacity * TSize);
69 
70     // Copy the elements over.  No need to run dtors on PODs.
71     memcpy(NewElts, this->BeginX, size() * TSize);
72   } else {
73     // If this wasn't grown from the inline copy, grow the allocated space.
74     NewElts = safe_realloc(this->BeginX, NewCapacity * TSize);
75   }
76 
77   this->BeginX = NewElts;
78   this->Capacity = NewCapacity;
79 }
80 
81 template class llvm::SmallVectorBase<uint32_t>;
82 
83 // Disable the uint64_t instantiation for 32-bit builds.
84 // Both uint32_t and uint64_t instantations are needed for 64-bit builds.
85 // This instantiation will never be used in 32-bit builds, and will cause
86 // warnings when sizeof(Size_T) > sizeof(size_t).
87 #if SIZE_MAX > UINT32_MAX
88 template class llvm::SmallVectorBase<uint64_t>;
89 
90 // Assertions to ensure this #if stays in sync with SmallVectorSizeType.
91 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t),
92               "Expected SmallVectorBase<uint64_t> variant to be in use.");
93 #else
94 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),
95               "Expected SmallVectorBase<uint32_t> variant to be in use.");
96 #endif
97