1 files changed, 74 insertions, 0 deletions
diff --git a/lld/MachO/MergedOutputSection.cpp b/lld/MachO/MergedOutputSection.cpp
new file mode 100644
index 000000000000..2d0be2538347
--- /dev/null
+++ b/lld/MachO/MergedOutputSection.cpp
@@ -0,0 +1,74 @@
+//===- OutputSection.cpp --------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "MergedOutputSection.h"
+#include "lld/Common/ErrorHandler.h"
+#include "lld/Common/Memory.h"
+#include "llvm/BinaryFormat/MachO.h"
+
+using namespace llvm;
+using namespace llvm::MachO;
+using namespace lld;
+using namespace lld::macho;
+
+void MergedOutputSection::mergeInput(InputSection *input) {
+  if (inputs.empty()) {
+    align = input->align;
+    flags = input->flags;
+  } else {
+    mergeFlags(input->flags);
+    align = std::max(align, input->align);
+  }
+
+  inputs.push_back(input);
+  input->parent = this;
+}
+
+void MergedOutputSection::finalize() {
+  uint64_t isecAddr = addr;
+  uint64_t isecFileOff = fileOff;
+  for (InputSection *isec : inputs) {
+    isecAddr = alignTo(isecAddr, isec->align);
+    isecFileOff = alignTo(isecFileOff, isec->align);
+    isec->outSecOff = isecAddr - addr;
+    isec->outSecFileOff = isecFileOff - fileOff;
+    isecAddr += isec->getSize();
+    isecFileOff += isec->getFileSize();
+  }
+  size = isecAddr - addr;
+  fileSize = isecFileOff - fileOff;
+}
+
+void MergedOutputSection::writeTo(uint8_t *buf) const {
+  for (InputSection *isec : inputs) {
+    isec->writeTo(buf + isec->outSecFileOff);
+  }
+}
+
+// TODO: this is most likely wrong; reconsider how section flags
+// are actually merged. The logic presented here was written without
+// any form of informed research.
+void MergedOutputSection::mergeFlags(uint32_t inputFlags) {
+  uint8_t sectionFlag = MachO::SECTION_TYPE & inputFlags;
+  if (sectionFlag != (MachO::SECTION_TYPE & flags))
+    error("Cannot add merge section; inconsistent type flags " +
+          Twine(sectionFlag));
+
+  uint32_t inconsistentFlags =
+      MachO::S_ATTR_DEBUG | MachO::S_ATTR_STRIP_STATIC_SYMS |
+      MachO::S_ATTR_NO_DEAD_STRIP | MachO::S_ATTR_LIVE_SUPPORT;
+  if ((inputFlags ^ flags) & inconsistentFlags)
+    error("Cannot add merge section; cannot merge inconsistent flags");
+
+  // Negate pure instruction presence if any section isn't pure.
+  uint32_t pureMask = ~MachO::S_ATTR_PURE_INSTRUCTIONS | (inputFlags & flags);
+
+  // Merge the rest
+  flags |= inputFlags;
+  flags &= pureMask;
+}