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Fix a performance problem in memcpyopt by removing a linear scan over ranges when inserting a new range. No functionality change intended. Patch by Anthony Pesch! 

llvm-svn: 242843
This commit is contained in:
Nick Lewycky 2015-07-21 21:56:26 +00:00
parent d058ea927f
commit f836c89c49
1 changed files with 9 additions and 16 deletions
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25
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -30,7 +30,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include <list>
#include <algorithm>
using namespace llvm;
#define DEBUG_TYPE "memcpyopt"
@ -200,15 +200,14 @@ bool MemsetRange::isProfitableToUseMemset(const DataLayout &DL) const {
namespace {
class MemsetRanges {
/// Ranges - A sorted list of the memset ranges. We use std::list here
/// because each element is relatively large and expensive to copy.
std::list<MemsetRange> Ranges;
typedef std::list<MemsetRange>::iterator range_iterator;
/// Ranges - A sorted list of the memset ranges.
SmallVector<MemsetRange, 8> Ranges;
typedef SmallVectorImpl<MemsetRange>::iterator range_iterator;
const DataLayout &DL;
public:
MemsetRanges(const DataLayout &DL) : DL(DL) {}
typedef std::list<MemsetRange>::const_iterator const_iterator;
typedef SmallVectorImpl<MemsetRange>::const_iterator const_iterator;
const_iterator begin() const { return Ranges.begin(); }
const_iterator end() const { return Ranges.end(); }
bool empty() const { return Ranges.empty(); }
@ -243,23 +242,17 @@ public:
/// addRange - Add a new store to the MemsetRanges data structure. This adds a
/// new range for the specified store at the specified offset, merging into
/// existing ranges as appropriate.
///
/// Do a linear search of the ranges to see if this can be joined and/or to
/// find the insertion point in the list. We keep the ranges sorted for
/// simplicity here. This is a linear search of a linked list, which is ugly,
/// however the number of ranges is limited, so this won't get crazy slow.
void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
unsigned Alignment, Instruction *Inst) {
int64_t End = Start+Size;
range_iterator I = Ranges.begin(), E = Ranges.end();
while (I != E && Start > I->End)
++I;
range_iterator I = std::lower_bound(Ranges.begin(), Ranges.end(), Start,
[](const MemsetRange &LHS, int64_t RHS) { return LHS.End < RHS; });
// We now know that I == E, in which case we didn't find anything to merge
// with, or that Start <= I->End. If End < I->Start or I == E, then we need
// to insert a new range. Handle this now.
if (I == E || End < I->Start) {
if (I == Ranges.end() || End < I->Start) {
MemsetRange &R = *Ranges.insert(I, MemsetRange());
R.Start = Start;
R.End = End;
@ -295,7 +288,7 @@ void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
if (End > I->End) {
I->End = End;
range_iterator NextI = I;
while (++NextI != E && End >= NextI->Start) {
while (++NextI != Ranges.end() && End >= NextI->Start) {
// Merge the range in.
I->TheStores.append(NextI->TheStores.begin(), NextI->TheStores.end());
if (NextI->End > I->End)