Generate slightly more compressed binding opcodes when entries are the same as last time.

We already had logic for binding opcodes had the same addend as last time.  This adds
the cases where the ordinal, symbol name, type, and segment offsets are the same as
the last emitted ordinal.

This gets us one step closer to emitting rebase opcodes as compressed as ld64 can manage.

llvm-svn: 278405

1 files changed, 37 insertions, 12 deletions

diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileBinaryWriter.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileBinaryWriter.cpp
index 8cca2a217c4..188ad3b9367 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileBinaryWriter.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileBinaryWriter.cpp
@@ -1192,19 +1192,44 @@ void MachOFileLayout::buildRebaseInfo() {
 void MachOFileLayout::buildBindInfo() {
   // TODO: compress bind info.
   uint64_t lastAddend = 0;
+  int lastOrdinal = 0x80000000;
+  StringRef lastSymbolName;
+  BindType lastType = (BindType)0;
+  Hex32 lastSegOffset = ~0U;
+  uint8_t lastSegIndex = (uint8_t)~0U;
   for (const BindLocation& entry : _file.bindingInfo) {
-    _bindingInfo.append_byte(BIND_OPCODE_SET_TYPE_IMM | entry.kind);
-    _bindingInfo.append_byte(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB
-                            | entry.segIndex);
-    _bindingInfo.append_uleb128(entry.segOffset);
-    if (entry.ordinal > 0)
-      _bindingInfo.append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_IMM |
-                               (entry.ordinal & 0xF));
-    else
-      _bindingInfo.append_byte(BIND_OPCODE_SET_DYLIB_SPECIAL_IMM |
-                               (entry.ordinal & 0xF));
-    _bindingInfo.append_byte(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM);
-    _bindingInfo.append_string(entry.symbolName);
+    if (entry.ordinal != lastOrdinal) {
+      if (entry.ordinal <= 0)
+        _bindingInfo.append_byte(BIND_OPCODE_SET_DYLIB_SPECIAL_IMM |
+                                 (entry.ordinal & BIND_IMMEDIATE_MASK));
+      else if (entry.ordinal <= BIND_IMMEDIATE_MASK)
+        _bindingInfo.append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_IMM |
+                                 entry.ordinal);
+      else {
+        _bindingInfo.append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB);
+        _bindingInfo.append_uleb128(entry.ordinal);
+      }
+      lastOrdinal = entry.ordinal;
+    }
+
+    if (lastSymbolName != entry.symbolName) {
+      _bindingInfo.append_byte(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM);
+      _bindingInfo.append_string(entry.symbolName);
+      lastSymbolName = entry.symbolName;
+    }
+
+    if (lastType != entry.kind) {
+      _bindingInfo.append_byte(BIND_OPCODE_SET_TYPE_IMM | entry.kind);
+      lastType = entry.kind;
+    }
+
+    if (lastSegIndex != entry.segIndex || lastSegOffset != entry.segOffset) {
+      _bindingInfo.append_byte(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB
+                               | entry.segIndex);
+      _bindingInfo.append_uleb128(entry.segOffset);
+      lastSegIndex = entry.segIndex;
+      lastSegOffset = entry.segOffset;
+    }
     if (entry.addend != lastAddend) {
       _bindingInfo.append_byte(BIND_OPCODE_SET_ADDEND_SLEB);
       _bindingInfo.append_sleb128(entry.addend);