Extract an utility for computing symbol sizes on MachO and COFF.

I will add a second user in the next commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240366 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Object/SymbolSize.cpp

@@ -0,0 +1,88 @@
+//===- SymbolSize.cpp -----------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Object/SymbolSize.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Object/ELFObjectFile.h"
+
+using namespace llvm;
+using namespace object;
+
+namespace {
+struct SymEntry {
+  symbol_iterator I;
+  uint64_t Address;
+  unsigned Number;
+  SectionRef Section;
+};
+}
+
+static int compareAddress(const SymEntry *A, const SymEntry *B) {
+  if (A->Section == B->Section)
+    return A->Address - B->Address;
+  if (A->Section < B->Section)
+    return -1;
+  return 1;
+}
+
+static int compareNumber(const SymEntry *A, const SymEntry *B) {
+  return A->Number - B->Number;
+}
+
+ErrorOr<std::vector<std::pair<SymbolRef, uint64_t>>>
+llvm::object::computeSymbolSizes(const ObjectFile &O) {
+  std::vector<std::pair<SymbolRef, uint64_t>> Ret;
+
+  if (isa<ELFObjectFileBase>(&O)) {
+    for (SymbolRef Sym : O.symbols()) {
+      Ret.push_back({Sym, Sym.getSize()});
+    }
+    return Ret;
+  }
+
+  // Collect sorted symbol addresses. Include dummy addresses for the end
+  // of each section.
+  std::vector<SymEntry> Addresses;
+  unsigned SymNum = 0;
+  for (symbol_iterator I = O.symbol_begin(), E = O.symbol_end(); I != E; ++I) {
+    SymbolRef Sym = *I;
+    uint64_t Address;
+    if (std::error_code EC = Sym.getAddress(Address))
+      return EC;
+    section_iterator SecI = O.section_end();
+    if (std::error_code EC = Sym.getSection(SecI))
+      return EC;
+    Addresses.push_back({I, Address, SymNum, *SecI});
+    ++SymNum;
+  }
+  for (const SectionRef Sec : O.sections()) {
+    uint64_t Address = Sec.getAddress();
+    uint64_t Size = Sec.getSize();
+    Addresses.push_back({O.symbol_end(), Address + Size, 0, Sec});
+  }
+  array_pod_sort(Addresses.begin(), Addresses.end(), compareAddress);
+
+  // Compute the size as the gap to the next symbol
+  for (unsigned I = 0, N = Addresses.size() - 1; I < N; ++I) {
+    auto &P = Addresses[I];
+    if (P.I == O.symbol_end())
+      continue;
+    uint64_t Size = Addresses[I + 1].Address - P.Address;
+    P.Address = Size;
+  }
+
+  // Put back in the original order and copy the result
+  array_pod_sort(Addresses.begin(), Addresses.end(), compareNumber);
+  for (SymEntry &P : Addresses) {
+    if (P.I == O.symbol_end())
+      continue;
+    Ret.push_back({*P.I, P.Address});
+  }
+  return Ret;
+}