<div dir="ltr">Be very careful with this code (e.g. changing data layouts). We spend over 20% of non-LTO time in it last time I looked (mostly the call to lower_bound IIRC).<div><br></div><div>-- Sean Silva</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, May 21, 2016 at 5:13 PM, Rui Ueyama via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: ruiu<br>
Date: Sat May 21 19:13:04 2016<br>
New Revision: 270340<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=270340&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=270340&view=rev</a><br>
Log:<br>
Define SectionPiece and use it instead of std::pair<uint_t, uint_t>.<br>
<br>
We were using std::pair to represents pieces of splittable section<br>
contents. It hurt readability because "first" and "second" are not<br>
meaningful. This patch give them names.<br>
<br>
One more thing is that piecewise liveness information is stored to<br>
the second element of the pair as a special value of output section<br>
offset. It was confusing, so I defiend a new bit, "Live", in the<br>
new struct.<br>
<br>
Modified:<br>
lld/trunk/ELF/InputSection.cpp<br>
lld/trunk/ELF/InputSection.h<br>
lld/trunk/ELF/MarkLive.cpp<br>
lld/trunk/ELF/OutputSections.cpp<br>
lld/trunk/ELF/Writer.cpp<br>
<br>
Modified: lld/trunk/ELF/InputSection.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=270340&r1=270339&r2=270340&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=270340&r1=270339&r2=270340&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/ELF/InputSection.cpp (original)<br>
+++ lld/trunk/ELF/InputSection.cpp Sat May 21 19:13:04 2016<br>
@@ -414,13 +414,12 @@ typename ELFT::uint EHInputSection<ELFT><br>
// identify the start of the output .eh_frame. Handle this special case.<br>
if (this->getSectionHdr()->sh_size == 0)<br>
return Offset;<br>
- std::pair<uintX_t, uintX_t> *I = this->getRangeAndSize(Offset).first;<br>
- uintX_t Base = I->second;<br>
- if (Base == uintX_t(-1))<br>
+ SectionPiece *Piece = this->getRangeAndSize(Offset).first;<br>
+ if (Piece->OutputOff == size_t(-1))<br>
return -1; // Not in the output<br>
<br>
- uintX_t Addend = Offset - I->first;<br>
- return Base + Addend;<br>
+ uintX_t Addend = Offset - Piece->InputOff;<br>
+ return Piece->OutputOff + Addend;<br>
}<br>
<br>
static size_t findNull(StringRef S, size_t EntSize) {<br>
@@ -443,17 +442,14 @@ MergeInputSection<ELFT>::MergeInputSecti<br>
uintX_t EntSize = Header->sh_entsize;<br>
ArrayRef<uint8_t> D = this->getSectionData();<br>
StringRef Data((const char *)D.data(), D.size());<br>
- std::vector<std::pair<uintX_t, uintX_t>> &Offsets = this->Offsets;<br>
<br>
- uintX_t V = Config->GcSections ? MergeInputSection<ELFT>::PieceDead<br>
- : MergeInputSection<ELFT>::PieceLive;<br>
if (Header->sh_flags & SHF_STRINGS) {<br>
uintX_t Offset = 0;<br>
while (!Data.empty()) {<br>
size_t End = findNull(Data, EntSize);<br>
if (End == StringRef::npos)<br>
fatal("string is not null terminated");<br>
- Offsets.push_back(std::make_pair(Offset, V));<br>
+ this->Pieces.emplace_back(Offset);<br>
uintX_t Size = End + EntSize;<br>
Data = Data.substr(Size);<br>
Offset += Size;<br>
@@ -465,7 +461,7 @@ MergeInputSection<ELFT>::MergeInputSecti<br>
size_t Size = Data.size();<br>
assert((Size % EntSize) == 0);<br>
for (unsigned I = 0, N = Size; I != N; I += EntSize)<br>
- Offsets.push_back(std::make_pair(I, V));<br>
+ this->Pieces.emplace_back(I);<br>
}<br>
<br>
template <class ELFT><br>
@@ -474,8 +470,7 @@ bool MergeInputSection<ELFT>::classof(co<br>
}<br>
<br>
template <class ELFT><br>
-std::pair<std::pair<typename ELFT::uint, typename ELFT::uint> *,<br>
- typename ELFT::uint><br>
+std::pair<SectionPiece *, typename ELFT::uint><br>
SplitInputSection<ELFT>::getRangeAndSize(uintX_t Offset) {<br>
ArrayRef<uint8_t> D = this->getSectionData();<br>
StringRef Data((const char *)D.data(), D.size());<br>
@@ -485,37 +480,32 @@ SplitInputSection<ELFT>::getRangeAndSize<br>
<br>
// Find the element this offset points to.<br>
auto I = std::upper_bound(<br>
- Offsets.begin(), Offsets.end(), Offset,<br>
- [](const uintX_t &A, const std::pair<uintX_t, uintX_t> &B) {<br>
- return A < B.first;<br>
- });<br>
- uintX_t End = I == Offsets.end() ? Data.size() : I->first;<br>
+ Pieces.begin(), Pieces.end(), Offset,<br>
+ [](const uintX_t &A, const SectionPiece &B) { return A < B.InputOff; });<br>
+ uintX_t End = (I == Pieces.end()) ? Data.size() : I->InputOff;<br>
--I;<br>
- return std::make_pair(&*I, End);<br>
+ return {&*I, End};<br>
}<br>
<br>
template <class ELFT><br>
typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) {<br>
- std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =<br>
- this->getRangeAndSize(Offset);<br>
- std::pair<uintX_t, uintX_t> *I = T.first;<br>
+ std::pair<SectionPiece *, uintX_t> T = this->getRangeAndSize(Offset);<br>
+ SectionPiece &Piece = *T.first;<br>
uintX_t End = T.second;<br>
- uintX_t Start = I->first;<br>
+ assert(Piece.Live);<br>
<br>
// Compute the Addend and if the Base is cached, return.<br>
- uintX_t Addend = Offset - Start;<br>
- uintX_t &Base = I->second;<br>
- assert(Base != MergeInputSection<ELFT>::PieceDead);<br>
- if (Base != MergeInputSection<ELFT>::PieceLive)<br>
- return Base + Addend;<br>
+ uintX_t Addend = Offset - Piece.InputOff;<br>
+ if (Piece.OutputOff != size_t(-1))<br>
+ return Piece.OutputOff + Addend;<br>
<br>
// Map the base to the offset in the output section and cache it.<br>
ArrayRef<uint8_t> D = this->getSectionData();<br>
StringRef Data((const char *)D.data(), D.size());<br>
- StringRef Entry = Data.substr(Start, End - Start);<br>
+ StringRef Entry = Data.substr(Piece.InputOff, End - Piece.InputOff);<br>
auto *MOS = static_cast<MergeOutputSection<ELFT> *>(this->OutSec);<br>
- Base = MOS->getOffset(Entry);<br>
- return Base + Addend;<br>
+ Piece.OutputOff = MOS->getOffset(Entry);<br>
+ return Piece.OutputOff + Addend;<br>
}<br>
<br>
template <class ELFT><br>
<br>
Modified: lld/trunk/ELF/InputSection.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.h?rev=270340&r1=270339&r2=270340&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.h?rev=270340&r1=270339&r2=270340&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/ELF/InputSection.h (original)<br>
+++ lld/trunk/ELF/InputSection.h Sat May 21 19:13:04 2016<br>
@@ -130,6 +130,14 @@ public:<br>
<br>
template <class ELFT> InputSectionBase<ELFT> InputSectionBase<ELFT>::Discarded;<br>
<br>
+// SectionPiece represents a piece of splittable section contents.<br>
+struct SectionPiece {<br>
+ SectionPiece(size_t I) : InputOff(I), Live(!Config->GcSections) {}<br>
+ size_t InputOff;<br>
+ size_t OutputOff = -1;<br>
+ bool Live;<br>
+};<br>
+<br>
// Usually sections are copied to the output as atomic chunks of data,<br>
// but some special types of sections are split into small pieces of data<br>
// and each piece is copied to a different place in the output.<br>
@@ -142,24 +150,11 @@ public:<br>
SplitInputSection(ObjectFile<ELFT> *File, const Elf_Shdr *Header,<br>
typename InputSectionBase<ELFT>::Kind SectionKind);<br>
<br>
- // For each piece of data, we maintain the offsets in the input section and<br>
- // in the output section.<br>
- std::vector<std::pair<uintX_t, uintX_t>> Offsets;<br>
-<br>
- // Merge input sections may use the following special values as the output<br>
- // section offset:<br>
- enum {<br>
- // The piece is dead.<br>
- PieceDead = uintX_t(-1),<br>
- // The piece is live, but an offset has not yet been assigned. After offsets<br>
- // have been assigned, if the output section uses tail merging, the field<br>
- // will still have this value and the output section offset is computed<br>
- // lazilly.<br>
- PieceLive = uintX_t(-2),<br>
- };<br>
+ // Splittable sections are handled as a sequence of data<br>
+ // rather than a single large blob of data.<br>
+ std::vector<SectionPiece> Pieces;<br>
<br>
- std::pair<std::pair<uintX_t, uintX_t> *, uintX_t><br>
- getRangeAndSize(uintX_t Offset);<br>
+ std::pair<SectionPiece *, uintX_t> getRangeAndSize(uintX_t Offset);<br>
};<br>
<br>
// This corresponds to a SHF_MERGE section of an input file.<br>
<br>
Modified: lld/trunk/ELF/MarkLive.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/MarkLive.cpp?rev=270340&r1=270339&r2=270340&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/MarkLive.cpp?rev=270340&r1=270339&r2=270340&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/ELF/MarkLive.cpp (original)<br>
+++ lld/trunk/ELF/MarkLive.cpp Sat May 21 19:13:04 2016<br>
@@ -143,9 +143,8 @@ template <class ELFT> void elf::markLive<br>
if (!R.Sec)<br>
return;<br>
if (auto *MS = dyn_cast<MergeInputSection<ELFT>>(R.Sec)) {<br>
- std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =<br>
- MS->getRangeAndSize(R.Offset);<br>
- T.first->second = MergeInputSection<ELFT>::PieceLive;<br>
+ std::pair<SectionPiece *, uintX_t> T = MS->getRangeAndSize(R.Offset);<br>
+ T.first->Live = true;<br>
}<br>
if (R.Sec->Live)<br>
return;<br>
<br>
Modified: lld/trunk/ELF/OutputSections.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=270340&r1=270339&r2=270340&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=270340&r1=270339&r2=270340&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/ELF/OutputSections.cpp (original)<br>
+++ lld/trunk/ELF/OutputSections.cpp Sat May 21 19:13:04 2016<br>
@@ -978,10 +978,9 @@ EHRegion<ELFT>::EHRegion(EHInputSection<<br>
<br>
template <class ELFT> StringRef EHRegion<ELFT>::data() const {<br>
ArrayRef<uint8_t> SecData = S->getSectionData();<br>
- ArrayRef<std::pair<uintX_t, uintX_t>> Offsets = S->Offsets;<br>
- size_t Start = Offsets[Index].first;<br>
- size_t End =<br>
- Index == Offsets.size() - 1 ? SecData.size() : Offsets[Index + 1].first;<br>
+ size_t Start = S->Pieces[Index].InputOff;<br>
+ size_t End = (Index == S->Pieces.size() - 1) ? SecData.size()<br>
+ : S->Pieces[Index + 1].InputOff;<br>
return StringRef((const char *)SecData.data() + Start, End - Start);<br>
}<br>
<br>
@@ -1142,8 +1141,8 @@ void EHOutputSection<ELFT>::addSectionAu<br>
<br>
DenseMap<uintX_t, uintX_t> OffsetToIndex;<br>
while (!D.empty()) {<br>
- unsigned Index = S->Offsets.size();<br>
- S->Offsets.push_back(std::make_pair(Offset, -1));<br>
+ unsigned Index = S->Pieces.size();<br>
+ S->Pieces.emplace_back(Offset);<br>
<br>
uintX_t Length = readEntryLength<ELFT>(D);<br>
// If CIE/FDE data length is zero then Length is 4, this<br>
@@ -1227,11 +1226,11 @@ template <class ELFT> void EHOutputSecti<br>
<br>
size_t Offset = 0;<br>
for (const Cie<ELFT> &C : Cies) {<br>
- C.S->Offsets[C.Index].second = Offset;<br>
+ C.S->Pieces[C.Index].OutputOff = Offset;<br>
Offset += alignTo(C.data().size(), sizeof(uintX_t));<br>
<br>
for (const EHRegion<ELFT> &F : C.Fdes) {<br>
- F.S->Offsets[F.Index].second = Offset;<br>
+ F.S->Pieces[F.Index].OutputOff = Offset;<br>
Offset += alignTo(F.data().size(), sizeof(uintX_t));<br>
}<br>
}<br>
@@ -1240,11 +1239,11 @@ template <class ELFT> void EHOutputSecti<br>
template <class ELFT> void EHOutputSection<ELFT>::writeTo(uint8_t *Buf) {<br>
const endianness E = ELFT::TargetEndianness;<br>
for (const Cie<ELFT> &C : Cies) {<br>
- size_t CieOffset = C.S->Offsets[C.Index].second;<br>
+ size_t CieOffset = C.S->Pieces[C.Index].OutputOff;<br>
writeCieFde<ELFT>(Buf + CieOffset, C.data());<br>
<br>
for (const EHRegion<ELFT> &F : C.Fdes) {<br>
- size_t Offset = F.S->Offsets[F.Index].second;<br>
+ size_t Offset = F.S->Pieces[F.Index].OutputOff;<br>
writeCieFde<ELFT>(Buf + Offset, F.data());<br>
write32<E>(Buf + Offset + 4, Offset + 4 - CieOffset); // Pointer<br>
<br>
@@ -1284,32 +1283,30 @@ void MergeOutputSection<ELFT>::addSectio<br>
StringRef Data((const char *)D.data(), D.size());<br>
uintX_t EntSize = S->getSectionHdr()->sh_entsize;<br>
this->Header.sh_entsize = EntSize;<br>
- MutableArrayRef<std::pair<uintX_t, uintX_t>> Offsets = S->Offsets;<br>
<br>
// If this is of type string, the contents are null-terminated strings.<br>
if (this->Header.sh_flags & SHF_STRINGS) {<br>
- for (unsigned I = 0, N = Offsets.size(); I != N; ++I) {<br>
- auto &P = Offsets[I];<br>
- if (P.second == MergeInputSection<ELFT>::PieceDead)<br>
+ for (unsigned I = 0, N = S->Pieces.size(); I != N; ++I) {<br>
+ SectionPiece &Piece = S->Pieces[I];<br>
+ if (!Piece.Live)<br>
continue;<br>
<br>
- uintX_t Start = P.first;<br>
- uintX_t End = (I == N - 1) ? Data.size() : Offsets[I + 1].first;<br>
+ uintX_t Start = Piece.InputOff;<br>
+ uintX_t End = (I == N - 1) ? Data.size() : S->Pieces[I + 1].InputOff;<br>
StringRef Entry = Data.substr(Start, End - Start);<br>
uintX_t OutputOffset = Builder.add(Entry);<br>
- if (shouldTailMerge())<br>
- OutputOffset = MergeInputSection<ELFT>::PieceLive;<br>
- P.second = OutputOffset;<br>
+ if (!shouldTailMerge())<br>
+ Piece.OutputOff = OutputOffset;<br>
}<br>
return;<br>
}<br>
<br>
// If this is not of type string, every entry has the same size.<br>
- for (auto &P : Offsets) {<br>
- if (P.second == (uintX_t)-1)<br>
+ for (SectionPiece &Piece : S->Pieces) {<br>
+ if (!Piece.Live)<br>
continue;<br>
- StringRef Entry = Data.substr(P.first, EntSize);<br>
- P.second = Builder.add(Entry);<br>
+ StringRef Entry = Data.substr(Piece.InputOff, EntSize);<br>
+ Piece.OutputOff = Builder.add(Entry);<br>
}<br>
}<br>
<br>
<br>
Modified: lld/trunk/ELF/Writer.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=270340&r1=270339&r2=270340&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=270340&r1=270339&r2=270340&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/ELF/Writer.cpp (original)<br>
+++ lld/trunk/ELF/Writer.cpp Sat May 21 19:13:04 2016<br>
@@ -855,8 +855,7 @@ template <class ELFT> static bool includ<br>
if (!D->Section->Live)<br>
return false;<br>
if (auto *S = dyn_cast<MergeInputSection<ELFT>>(D->Section))<br>
- if (S->getRangeAndSize(D->Value).first->second ==<br>
- MergeInputSection<ELFT>::PieceDead)<br>
+ if (!S->getRangeAndSize(D->Value).first->Live)<br>
return false;<br>
}<br>
return true;<br>
<br>
<br>
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</blockquote></div><br></div>