Imported Upstream version 5.18.0.161

Former-commit-id: 4db48158d3a35497b8f118ab21b5f08ac3d86d98

external/llvm/lib/MC/StringTableBuilder.cpp

@@ -0,0 +1,187 @@
+//===- StringTableBuilder.cpp - String table building utility -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/StringTableBuilder.h"
+#include "llvm/ADT/CachedHashString.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/BinaryFormat/COFF.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+
+StringTableBuilder::~StringTableBuilder() = default;
+
+void StringTableBuilder::initSize() {
+  // Account for leading bytes in table so that offsets returned from add are
+  // correct.
+  switch (K) {
+  case RAW:
+    Size = 0;
+    break;
+  case MachO:
+  case ELF:
+    // Start the table with a NUL byte.
+    Size = 1;
+    break;
+  case WinCOFF:
+    // Make room to write the table size later.
+    Size = 4;
+    break;
+  }
+}
+
+StringTableBuilder::StringTableBuilder(Kind K, unsigned Alignment)
+    : K(K), Alignment(Alignment) {
+  initSize();
+}
+
+void StringTableBuilder::write(raw_ostream &OS) const {
+  assert(isFinalized());
+  SmallString<0> Data;
+  Data.resize(getSize());
+  write((uint8_t *)Data.data());
+  OS << Data;
+}
+
+using StringPair = std::pair<CachedHashStringRef, size_t>;
+
+void StringTableBuilder::write(uint8_t *Buf) const {
+  assert(isFinalized());
+  for (const StringPair &P : StringIndexMap) {
+    StringRef Data = P.first.val();
+    if (!Data.empty())
+      memcpy(Buf + P.second, Data.data(), Data.size());
+  }
+  if (K != WinCOFF)
+    return;
+  support::endian::write32le(Buf, Size);
+}
+
+// Returns the character at Pos from end of a string.
+static int charTailAt(StringPair *P, size_t Pos) {
+  StringRef S = P->first.val();
+  if (Pos >= S.size())
+    return -1;
+  return (unsigned char)S[S.size() - Pos - 1];
+}
+
+// Three-way radix quicksort. This is much faster than std::sort with strcmp
+// because it does not compare characters that we already know the same.
+static void multikeySort(MutableArrayRef<StringPair *> Vec, int Pos) {
+tailcall:
+  if (Vec.size() <= 1)
+    return;
+
+  // Partition items so that items in [0, I) are greater than the pivot,
+  // [I, J) are the same as the pivot, and [J, Vec.size()) are less than
+  // the pivot.
+  int Pivot = charTailAt(Vec[0], Pos);
+  size_t I = 0;
+  size_t J = Vec.size();
+  for (size_t K = 1; K < J;) {
+    int C = charTailAt(Vec[K], Pos);
+    if (C > Pivot)
+      std::swap(Vec[I++], Vec[K++]);
+    else if (C < Pivot)
+      std::swap(Vec[--J], Vec[K]);
+    else
+      K++;
+  }
+
+  multikeySort(Vec.slice(0, I), Pos);
+  multikeySort(Vec.slice(J), Pos);
+
+  // multikeySort(Vec.slice(I, J - I), Pos + 1), but with
+  // tail call optimization.
+  if (Pivot != -1) {
+    Vec = Vec.slice(I, J - I);
+    ++Pos;
+    goto tailcall;
+  }
+}
+
+void StringTableBuilder::finalize() {
+  finalizeStringTable(/*Optimize=*/true);
+}
+
+void StringTableBuilder::finalizeInOrder() {
+  finalizeStringTable(/*Optimize=*/false);
+}
+
+void StringTableBuilder::finalizeStringTable(bool Optimize) {
+  Finalized = true;
+
+  if (Optimize) {
+    std::vector<StringPair *> Strings;
+    Strings.reserve(StringIndexMap.size());
+    for (StringPair &P : StringIndexMap)
+      Strings.push_back(&P);
+
+    multikeySort(Strings, 0);
+    initSize();
+
+    StringRef Previous;
+    for (StringPair *P : Strings) {
+      StringRef S = P->first.val();
+      if (Previous.endswith(S)) {
+        size_t Pos = Size - S.size() - (K != RAW);
+        if (!(Pos & (Alignment - 1))) {
+          P->second = Pos;
+          continue;
+        }
+      }
+
+      Size = alignTo(Size, Alignment);
+      P->second = Size;
+
+      Size += S.size();
+      if (K != RAW)
+        ++Size;
+      Previous = S;
+    }
+  }
+
+  if (K == MachO)
+    Size = alignTo(Size, 4); // Pad to multiple of 4.
+}
+
+void StringTableBuilder::clear() {
+  Finalized = false;
+  StringIndexMap.clear();
+}
+
+size_t StringTableBuilder::getOffset(CachedHashStringRef S) const {
+  assert(isFinalized());
+  auto I = StringIndexMap.find(S);
+  assert(I != StringIndexMap.end() && "String is not in table!");
+  return I->second;
+}
+
+size_t StringTableBuilder::add(CachedHashStringRef S) {
+  if (K == WinCOFF)
+    assert(S.size() > COFF::NameSize && "Short string in COFF string table!");
+
+  assert(!isFinalized());
+  auto P = StringIndexMap.insert(std::make_pair(S, 0));
+  if (P.second) {
+    size_t Start = alignTo(Size, Alignment);
+    P.first->second = Start;
+    Size = Start + S.size() + (K != RAW);
+  }
+  return P.first->second;
+}