2 files changed, 28 insertions, 2 deletions
diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFile.h b/lld/lib/ReaderWriter/MachO/MachONormalizedFile.h
index 400a30b8930..7934a6c0336 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFile.h
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFile.h
@@ -105,6 +105,9 @@ typedef std::vector<uint32_t> IndirectSymbols;
 /// A typedef so that YAML I/O can encode/decode section attributes.
 LLVM_YAML_STRONG_TYPEDEF(uint32_t, SectionAttr)
 
+/// A typedef so that YAML I/O can encode/decode section alignment.
+LLVM_YAML_STRONG_TYPEDEF(uint16_t, SectionAlignment)
+
 /// Mach-O has a 32-bit and 64-bit section record.  This normalized form
 /// can support either kind.
 struct Section {
@@ -115,7 +118,7 @@ struct Section {
   StringRef       sectionName;
   SectionType     type;
   SectionAttr     attributes;
-  uint16_t        alignment;
+  SectionAlignment        alignment;
   Hex64           address;
   ArrayRef<uint8_t> content;
   Relocations     relocations;
diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp
index 5ae9204f72b..aa3b042b557 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp
@@ -237,6 +237,29 @@ struct ScalarBitSetTraits<SectionAttr> {
   }
 };
 
+/// This is a custom formatter for SectionAlignment.  Values are
+/// the power to raise by, ie, the n in 2^n.
+template <> struct ScalarTraits<SectionAlignment> {
+  static void output(const SectionAlignment &value, void *ctxt,
+                     raw_ostream &out) {
+    out << llvm::format("%d", (uint32_t)value);
+  }
+
+  static StringRef input(StringRef scalar, void *ctxt,
+                         SectionAlignment &value) {
+    uint32_t alignment;
+    if (scalar.getAsInteger(0, alignment)) {
+      return "malformed alignment value";
+    }
+    if (!llvm::isPowerOf2_32(alignment))
+      return "alignment must be a power of 2";
+    value = alignment;
+    return StringRef(); // returning empty string means success
+  }
+
+  static bool mustQuote(StringRef) { return false; }
+};
+
 template <>
 struct ScalarEnumerationTraits<NListType> {
   static void enumeration(IO &io, NListType &value) {
@@ -276,7 +299,7 @@ struct MappingTraits<Section> {
     io.mapRequired("section",         sect.sectionName);
     io.mapRequired("type",            sect.type);
     io.mapOptional("attributes",      sect.attributes);
-    io.mapOptional("alignment",       sect.alignment, (uint16_t)1);
+    io.mapOptional("alignment",       sect.alignment, (SectionAlignment)1);
     io.mapRequired("address",         sect.address);
     if (isZeroFillSection(sect.type)) {
       // S_ZEROFILL sections use "size:" instead of "content:"