b5f0eae1dc
SmallVector currently uses 32bit integers for size and capacity to reduce sizeof(SmallVector). This limits the number of elements to UINT32_MAX. For a SmallVector<char>, this limits the SmallVector size to only 4GB. Buffering bitcode output uses SmallVector<char>, but needs >4GB output. This changes SmallVector size and capacity to conditionally use word-size integers if the element type is small (<4 bytes). For larger elements types, the vector size can reach ~16GB with 32bit size. Making this conditional on the element type provides both the smaller sizeof(SmallVector) for larger types which are unlikely to grow so large, and supports larger capacities for smaller element types.
82 lines
3.3 KiB
C++
82 lines
3.3 KiB
C++
//===- llvm/ADT/SmallVector.cpp - 'Normally small' vectors ----------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the SmallVector class.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/SmallVector.h"
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using namespace llvm;
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// Check that no bytes are wasted and everything is well-aligned.
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namespace {
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struct Struct16B {
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alignas(16) void *X;
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};
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struct Struct32B {
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alignas(32) void *X;
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};
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}
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static_assert(sizeof(SmallVector<void *, 0>) ==
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sizeof(unsigned) * 2 + sizeof(void *),
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"wasted space in SmallVector size 0");
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static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
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"wrong alignment for 16-byte aligned T");
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static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
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"wrong alignment for 32-byte aligned T");
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static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
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"missing padding for 16-byte aligned T");
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static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
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"missing padding for 32-byte aligned T");
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static_assert(sizeof(SmallVector<void *, 1>) ==
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sizeof(unsigned) * 2 + sizeof(void *) * 2,
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"wasted space in SmallVector size 1");
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static_assert(sizeof(SmallVector<char, 0>) ==
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sizeof(void *) * 2 + sizeof(void *),
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"1 byte elements have word-sized type for size and capacity");
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// Note: Moving this function into the header may cause performance regression.
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template <class Size_T>
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void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinCapacity,
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size_t TSize) {
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// Ensure we can fit the new capacity.
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// This is only going to be applicable when the capacity is 32 bit.
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if (MinCapacity > SizeTypeMax())
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report_bad_alloc_error("SmallVector capacity overflow during allocation");
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// Ensure we can meet the guarantee of space for at least one more element.
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// The above check alone will not catch the case where grow is called with a
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// default MinCapacity of 0, but the current capacity cannot be increased.
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// This is only going to be applicable when the capacity is 32 bit.
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if (capacity() == SizeTypeMax())
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report_bad_alloc_error("SmallVector capacity unable to grow");
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// In theory 2*capacity can overflow if the capacity is 64 bit, but the
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// original capacity would never be large enough for this to be a problem.
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size_t NewCapacity = 2 * capacity() + 1; // Always grow.
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NewCapacity = std::min(std::max(NewCapacity, MinCapacity), SizeTypeMax());
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void *NewElts;
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if (BeginX == FirstEl) {
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NewElts = safe_malloc(NewCapacity * TSize);
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// Copy the elements over. No need to run dtors on PODs.
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memcpy(NewElts, this->BeginX, size() * TSize);
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} else {
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// If this wasn't grown from the inline copy, grow the allocated space.
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NewElts = safe_realloc(this->BeginX, NewCapacity * TSize);
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}
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this->BeginX = NewElts;
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this->Capacity = NewCapacity;
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}
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template class llvm::SmallVectorBase<uint32_t>;
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template class llvm::SmallVectorBase<uintptr_t>;
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