[llvm] f005f6c - Revert "ADT: SmallVector size/capacity use word-size integers when elements are small"
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Sat Apr 18 02:47:08 PDT 2020
Author: Nikita Popov
Date: 2020-04-18T11:46:58+02:00
New Revision: f005f6c2343438b3760f2d6b5f396f42050cbd4d
URL: https://github.com/llvm/llvm-project/commit/f005f6c2343438b3760f2d6b5f396f42050cbd4d
DIFF: https://github.com/llvm/llvm-project/commit/f005f6c2343438b3760f2d6b5f396f42050cbd4d.diff
LOG: Revert "ADT: SmallVector size/capacity use word-size integers when elements are small"
This reverts commit b8d08e961df1d229872c785ebdbc8367432e9752.
This change causes a 1% compile-time and 1% memory usage regression:
http://llvm-compile-time-tracker.com/compare.php?from=73b7dd1fb3c17a4ac4b1f1e603f26fa708009649&to=b8d08e961df1d229872c785ebdbc8367432e9752&stat=instructions
http://llvm-compile-time-tracker.com/compare.php?from=73b7dd1fb3c17a4ac4b1f1e603f26fa708009649&to=b8d08e961df1d229872c785ebdbc8367432e9752&stat=max-rss
Added:
Modified:
llvm/include/llvm/ADT/SmallVector.h
llvm/lib/Support/SmallVector.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
index 0e5a56f085f0..28b514d530dc 100644
--- a/llvm/include/llvm/ADT/SmallVector.h
+++ b/llvm/include/llvm/ADT/SmallVector.h
@@ -16,10 +16,10 @@
#include "llvm/ADT/iterator_range.h"
#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Compiler.h"
-#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/MemAlloc.h"
#include "llvm/Support/type_traits.h"
+#include "llvm/Support/ErrorHandling.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
@@ -27,7 +27,6 @@
#include <cstring>
#include <initializer_list>
#include <iterator>
-#include <limits>
#include <memory>
#include <new>
#include <type_traits>
@@ -35,23 +34,11 @@
namespace llvm {
-/// This is all the stuff common to all SmallVectors.
-///
-/// The template parameter specifies the type which should be used to hold the
-/// Size and Capacity of the SmallVector, so it can be adjusted.
-/// Using 32 bit size is desirable to shink the size of the SmallVector.
-/// Using 64 bit size is desirable for cases like SmallVector<char>, where a
-/// 32 bit size would limit the vector to ~4GB. SmallVectors are used for
-/// buffering bitcode output - which can exceed 4GB.
-template <class Size_T> class SmallVectorBase {
+/// This is all the non-templated stuff common to all SmallVectors.
+class SmallVectorBase {
protected:
void *BeginX;
- Size_T Size = 0, Capacity;
-
- /// The maximum value of the Size_T used.
- static constexpr size_t SizeTypeMax() {
- return std::numeric_limits<Size_T>::max();
- }
+ unsigned Size = 0, Capacity;
SmallVectorBase() = delete;
SmallVectorBase(void *FirstEl, size_t TotalCapacity)
@@ -59,39 +46,7 @@ template <class Size_T> class SmallVectorBase {
/// This is an implementation of the grow() method which only works
/// on POD-like data types and is out of line to reduce code duplication.
- /// This function will report a fatal error if it cannot increase capacity.
- void grow_pod(void *FirstEl, size_t MinCapacity, size_t TSize) {
- // Ensure we can fit the new capacity.
- // This is only going to be applicable if the when the capacity is 32 bit.
- if (MinCapacity > SizeTypeMax())
- report_bad_alloc_error("SmallVector capacity overflow during allocation");
-
- // Ensure we can meet the guarantee of space for at least one more element.
- // The above check alone will not catch the case where grow is called with a
- // default MinCapacity of 0, but the current capacity cannot be increased.
- // This is only going to be applicable if the when the capacity is 32 bit.
- if (capacity() == SizeTypeMax())
- report_bad_alloc_error("SmallVector capacity unable to grow");
-
- // In theory 2*capacity can overflow if the capacity is 64 bit, but the
- // original capacity would never be large enough for this to be a problem.
- size_t NewCapacity = 2 * capacity() + 1; // Always grow.
- NewCapacity = std::min(std::max(NewCapacity, MinCapacity), SizeTypeMax());
-
- void *NewElts;
- if (BeginX == FirstEl) {
- NewElts = safe_malloc(NewCapacity * TSize);
-
- // Copy the elements over. No need to run dtors on PODs.
- memcpy(NewElts, this->BeginX, size() * TSize);
- } else {
- // If this wasn't grown from the inline copy, grow the allocated space.
- NewElts = safe_realloc(this->BeginX, NewCapacity * TSize);
- }
-
- this->BeginX = NewElts;
- this->Capacity = NewCapacity;
- }
+ void grow_pod(void *FirstEl, size_t MinCapacity, size_t TSize);
public:
size_t size() const { return Size; }
@@ -114,13 +69,9 @@ template <class Size_T> class SmallVectorBase {
}
};
-template <class T>
-using SmallVectorSizeType =
- typename std::conditional<sizeof(T) < 4, uintptr_t, uint32_t>::type;
-
/// Figure out the offset of the first element.
template <class T, typename = void> struct SmallVectorAlignmentAndSize {
- AlignedCharArrayUnion<SmallVectorBase<SmallVectorSizeType<T>>> Base;
+ AlignedCharArrayUnion<SmallVectorBase> Base;
AlignedCharArrayUnion<T> FirstEl;
};
@@ -128,10 +79,7 @@ template <class T, typename = void> struct SmallVectorAlignmentAndSize {
/// the type T is a POD. The extra dummy template argument is used by ArrayRef
/// to avoid unnecessarily requiring T to be complete.
template <typename T, typename = void>
-class SmallVectorTemplateCommon
- : public SmallVectorBase<SmallVectorSizeType<T>> {
- using Base = SmallVectorBase<SmallVectorSizeType<T>>;
-
+class SmallVectorTemplateCommon : public SmallVectorBase {
/// Find the address of the first element. For this pointer math to be valid
/// with small-size of 0 for T with lots of alignment, it's important that
/// SmallVectorStorage is properly-aligned even for small-size of 0.
@@ -143,20 +91,21 @@ class SmallVectorTemplateCommon
// Space after 'FirstEl' is clobbered, do not add any instance vars after it.
protected:
- SmallVectorTemplateCommon(size_t Size) : Base(getFirstEl(), Size) {}
+ SmallVectorTemplateCommon(size_t Size)
+ : SmallVectorBase(getFirstEl(), Size) {}
void grow_pod(size_t MinCapacity, size_t TSize) {
- Base::grow_pod(getFirstEl(), MinCapacity, TSize);
+ SmallVectorBase::grow_pod(getFirstEl(), MinCapacity, TSize);
}
/// Return true if this is a smallvector which has not had dynamic
/// memory allocated for it.
- bool isSmall() const { return this->BeginX == getFirstEl(); }
+ bool isSmall() const { return BeginX == getFirstEl(); }
/// Put this vector in a state of being small.
void resetToSmall() {
- this->BeginX = getFirstEl();
- this->Size = this->Capacity = 0; // FIXME: Setting Capacity to 0 is suspect.
+ BeginX = getFirstEl();
+ Size = Capacity = 0; // FIXME: Setting Capacity to 0 is suspect.
}
public:
@@ -174,10 +123,6 @@ class SmallVectorTemplateCommon
using pointer = T *;
using const_pointer = const T *;
- using Base::capacity;
- using Base::empty;
- using Base::size;
-
// forward iterator creation methods.
iterator begin() { return (iterator)this->BeginX; }
const_iterator begin() const { return (const_iterator)this->BeginX; }
@@ -191,9 +136,7 @@ class SmallVectorTemplateCommon
const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
size_type size_in_bytes() const { return size() * sizeof(T); }
- size_type max_size() const {
- return std::min(this->SizeTypeMax(), size_type(-1) / sizeof(T));
- }
+ size_type max_size() const { return size_type(-1) / sizeof(T); }
size_t capacity_in_bytes() const { return capacity() * sizeof(T); }
@@ -288,21 +231,12 @@ class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
// Define this out-of-line to dissuade the C++ compiler from inlining it.
template <typename T, bool TriviallyCopyable>
void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) {
- // Ensure we can fit the new capacity.
- // This is only going to be applicable if the when the capacity is 32 bit.
- if (MinSize > this->SizeTypeMax())
+ if (MinSize > UINT32_MAX)
report_bad_alloc_error("SmallVector capacity overflow during allocation");
- // Ensure we can meet the guarantee of space for at least one more element.
- // The above check alone will not catch the case where grow is called with a
- // default MinCapacity of 0, but the current capacity cannot be increased.
- // This is only going to be applicable if the when the capacity is 32 bit.
- if (this->capacity() == this->SizeTypeMax())
- report_bad_alloc_error("SmallVector capacity unable to grow");
-
// Always grow, even from zero.
size_t NewCapacity = size_t(NextPowerOf2(this->capacity() + 2));
- NewCapacity = std::min(std::max(NewCapacity, MinSize), this->SizeTypeMax());
+ NewCapacity = std::min(std::max(NewCapacity, MinSize), size_t(UINT32_MAX));
T *NewElts = static_cast<T*>(llvm::safe_malloc(NewCapacity*sizeof(T)));
// Move the elements over.
diff --git a/llvm/lib/Support/SmallVector.cpp b/llvm/lib/Support/SmallVector.cpp
index 0d1765ab3e5c..36f0a81f6b00 100644
--- a/llvm/lib/Support/SmallVector.cpp
+++ b/llvm/lib/Support/SmallVector.cpp
@@ -36,6 +36,30 @@ static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
static_assert(sizeof(SmallVector<void *, 1>) ==
sizeof(unsigned) * 2 + sizeof(void *) * 2,
"wasted space in SmallVector size 1");
-static_assert(sizeof(SmallVector<char, 0>) ==
- sizeof(void *) * 2 + sizeof(void *),
- "1 byte elements have word-sized type for size and capacity");
+
+/// 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 MinCapacity,
+ size_t TSize) {
+ // Ensure we can fit the new capacity in 32 bits.
+ if (MinCapacity > UINT32_MAX)
+ report_bad_alloc_error("SmallVector capacity overflow during allocation");
+
+ size_t NewCapacity = 2 * capacity() + 1; // Always grow.
+ NewCapacity =
+ std::min(std::max(NewCapacity, MinCapacity), size_t(UINT32_MAX));
+
+ void *NewElts;
+ if (BeginX == FirstEl) {
+ NewElts = safe_malloc(NewCapacity * TSize);
+
+ // Copy the elements over. No need to run dtors on PODs.
+ memcpy(NewElts, this->BeginX, size() * TSize);
+ } else {
+ // If this wasn't grown from the inline copy, grow the allocated space.
+ NewElts = safe_realloc(this->BeginX, NewCapacity * TSize);
+ }
+
+ this->BeginX = NewElts;
+ this->Capacity = NewCapacity;
+}
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