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llvm-mirror/lib/Support/SmallVector.cpp
Duncan P. N. Exon Smith e5c1811255 ADT: Use EBO to shrink SmallVector size 1
SmallVectorStorage is empty when its size is 1; use inheritance so that
the empty base class optimization kicks in.

llvm-svn: 335421
2018-06-23 18:39:44 +00:00

45 lines
1.6 KiB
C++

//===- llvm/ADT/SmallVector.cpp - 'Normally small' vectors ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the SmallVector class.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallVector.h"
using namespace llvm;
// Check that no bytes are wasted.
static_assert(sizeof(SmallVector<void *, 1>) == sizeof(void *) * 4,
"wasted space in SmallVector size 1; missing EBO?");
/// grow_pod - This is an implementation of the grow() method which only works
/// on POD-like datatypes and is out of line to reduce code duplication.
void SmallVectorBase::grow_pod(void *FirstEl, size_t MinSizeInBytes,
size_t TSize) {
size_t CurSizeBytes = size_in_bytes();
size_t NewCapacityInBytes = 2 * capacity_in_bytes() + TSize; // Always grow.
if (NewCapacityInBytes < MinSizeInBytes)
NewCapacityInBytes = MinSizeInBytes;
void *NewElts;
if (BeginX == FirstEl) {
NewElts = safe_malloc(NewCapacityInBytes);
// Copy the elements over. No need to run dtors on PODs.
memcpy(NewElts, this->BeginX, CurSizeBytes);
} else {
// If this wasn't grown from the inline copy, grow the allocated space.
NewElts = safe_realloc(this->BeginX, NewCapacityInBytes);
}
this->EndX = (char*)NewElts+CurSizeBytes;
this->BeginX = NewElts;
this->CapacityX = (char*)this->BeginX + NewCapacityInBytes;
}