From 0cb34615d9d1cdce408df1fc8ecc4368566e2ec6 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <rui314@gmail.com>
Date: Sun, 7 Nov 2021 18:59:17 +0900
Subject: [PATCH] [Mach-O] wip

---
 macho/mold.h           |  5 +++--
 macho/output-chunks.cc | 48 +++++++++++++++++++++++++++++++++++++++---
 2 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/macho/mold.h b/macho/mold.h
index 26d82b5d..83cf22ee 100644
--- a/macho/mold.h
+++ b/macho/mold.h
@@ -277,13 +277,14 @@ class RebaseEncoder {
 public:
   RebaseEncoder();
   void add(i64 seg_idx, i64 offset);
+  void flush();
   void finish();
 
   std::vector<u8> buf;
 
 private:
-  i64 last_seg = -1;
-  i64 last_off = 0;
+  i64 cur_seg = -1;
+  i64 cur_off = 0;
   i64 times = 0;
 };
 
diff --git a/macho/output-chunks.cc b/macho/output-chunks.cc
index 644f0cf3..c1dce436 100644
--- a/macho/output-chunks.cc
+++ b/macho/output-chunks.cc
@@ -422,12 +422,54 @@ RebaseEncoder::RebaseEncoder() {
 
 void RebaseEncoder::add(i64 seg_idx, i64 offset) {
   assert(seg_idx < 16);
-  buf.push_back(REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | seg_idx);
-  encode_uleb(buf, offset);
-  buf.push_back(REBASE_OPCODE_DO_REBASE_IMM_TIMES | 1);
+
+  // Accumulate consecutive base relocations
+  if (seg_idx == cur_seg && offset == cur_off) {
+    cur_off += 8;
+    times++;
+    return;
+  }
+
+  // Flush the accumulated base relocations
+  flush();
+
+  // Advance the cursor
+  if (seg_idx != cur_seg) {
+    buf.push_back(REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | seg_idx);
+    encode_uleb(buf, offset);
+  } else {
+    i64 dist = offset - cur_off;
+    assert(dist >= 0);
+
+    if (dist % 8 == 0 && dist < 128) {
+      buf.push_back(REBASE_OPCODE_ADD_ADDR_IMM_SCALED | (dist >> 3));
+    } else {
+      buf.push_back(REBASE_OPCODE_ADD_ADDR_ULEB);
+      encode_uleb(buf, dist);
+    }
+  }
+
+  cur_seg = seg_idx;
+  cur_off = offset + 8;
+  times = 1;
+}
+
+void RebaseEncoder::flush() {
+  if (times == 0)
+    return;
+
+  if (times < 16) {
+    buf.push_back(REBASE_OPCODE_DO_REBASE_IMM_TIMES | times);
+  } else {
+    buf.push_back(REBASE_OPCODE_DO_REBASE_ULEB_TIMES);
+    encode_uleb(buf, times);
+  }
+
+  times = 0;
 }
 
 void RebaseEncoder::finish() {
+  flush();
   buf.push_back(REBASE_OPCODE_DONE);
 }