ARM64: Avoid iterating through all unresolved branch infos when many are pending.

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index 9a8cd467a0f7b8425c6dabe754f9f7f89cc54686..b0dd3b84addd1a32cd059d09a78646e292f3d08b 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -1694,6 +1694,10 @@ class Assembler : public AssemblerBase {
     return reinterpret_cast<Instruction*>(buffer_ + offset);
   }
 
+  ptrdiff_t InstructionOffset(Instruction* instr) const {
+    return reinterpret_cast<byte*>(instr) - buffer_;
+  }
+
   // Register encoding.
   static Instr Rd(CPURegister rd) {
     ASSERT(rd.code() != kSPRegInternalCode);
@@ -2182,6 +2186,15 @@ class Assembler : public AssemblerBase {
   // not later attempt (likely unsuccessfully) to patch it to branch directly to
   // the label.
   void DeleteUnresolvedBranchInfoForLabel(Label* label);
+  // This function deletes the information related to the label by iterating
+  // through all unresolved branch infos and deleting the appropriating one. Its
+  // complexity is proportional to the number of unresolved branches pending.
+  void DeleteUnresolvedBranchInfoForLabelIterate(Label* label);
+  // This function deletes the information related to the label by traversing
+  // the label chain, and for each PC-relative instruction in the chain checking
+  // if pending unresolved information exists. Its complexity is proportional to
+  // the length of the label chain.
+  void DeleteUnresolvedBranchInfoForLabelTraverse(Label* label);
 
  private:
   PositionsRecorder positions_recorder_;