forked from OSchip/llvm-project
Simplify RelrSection<ELFT>::updateAllocSize.
This patch also speeds it up by making some constants compile-time constants. Other than that, NFC. Differential Revision: https://reviews.llvm.org/D49101 llvm-svn: 336614
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@ -1745,53 +1745,47 @@ template <class ELFT> bool RelrSection<ELFT>::updateAllocSize() {
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size_t OldSize = RelrRelocs.size();
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RelrRelocs.clear();
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// Same as Config->Wordsize but faster because this is a compile-time
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// constant.
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const size_t Wordsize = sizeof(typename ELFT::uint);
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// Number of bits to use for the relocation offsets bitmap.
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// These many relative relocations can be encoded in a single entry.
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const size_t NBits = 8 * Config->Wordsize - 1;
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// Must be either 63 or 31.
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const size_t NBits = Wordsize * 8 - 1;
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// Get offsets for all relative relocations and sort them.
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std::vector<uint64_t> Offsets;
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for (const RelativeReloc &Rel : Relocs) {
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for (const RelativeReloc &Rel : Relocs)
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Offsets.push_back(Rel.getOffset());
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}
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std::sort(Offsets.begin(), Offsets.end());
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llvm::sort(Offsets.begin(), Offsets.end());
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uint64_t Base = 0;
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typename std::vector<uint64_t>::iterator Curr = Offsets.begin();
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while (Curr != Offsets.end()) {
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uint64_t Current = *Curr;
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assert(Current % 2 == 0);
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// For each leading relocation, find following ones that can be folded
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// as a bitmap and fold them.
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for (size_t I = 0, E = Offsets.size(); I < E;) {
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// Add a leading relocation.
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RelrRelocs.push_back(Elf_Relr(Offsets[I]));
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++I;
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uint64_t Bits = 0;
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typename std::vector<uint64_t>::iterator Next = Curr;
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if (Base > 0 && Base <= Current) {
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while (Next != Offsets.end()) {
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uint64_t Delta = *Next - Base;
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// If Next is too far out, it cannot be folded into Curr.
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if (Delta >= NBits * Config->Wordsize)
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break;
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// If Next is not a multiple of wordsize away, it cannot
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// be folded into Curr.
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if (Delta % Config->Wordsize != 0)
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break;
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// Next can be folded into Curr, add it to the bitmap.
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Bits |= 1ULL << (Delta / Config->Wordsize);
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++Next;
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}
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// Find foldable relocations to create a bitmap.
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uint64_t Bitmap = 0;
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for (size_t J = I; J < E; ++J) {
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uint64_t Delta = Offsets[J] - Offsets[I];
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// If it is too far, it cannot be folded.
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if (Delta >= NBits * Wordsize)
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break;
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// If it is not a multiple of wordsize away, it cannot be folded.
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if (Delta % Wordsize)
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break;
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// Fold it.
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Bitmap |= 1ULL << (Delta / Wordsize);
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}
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if (Bits == 0) {
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RelrRelocs.push_back(Elf_Relr(Current));
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// This is not a continuation entry, only one offset was
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// consumed. Set base offset for subsequent bitmap entries.
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Base = Current + Config->Wordsize;
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++Curr;
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} else {
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RelrRelocs.push_back(Elf_Relr((Bits << 1) | 1));
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// This is a continuation entry encoding multiple offsets
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// in a bitmap. Advance base offset by NBits words.
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Base += NBits * Config->Wordsize;
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Curr = Next;
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if (Bitmap) {
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RelrRelocs.push_back(Elf_Relr((Bitmap << 1) | 1));
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I += NBits;
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}
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}
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