From ab5871e47236d3b82a31ed9ac68f0425cf62be5e Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas@devlieghere.com>
Date: Fri, 6 Oct 2023 08:00:48 -0700
Subject: [PATCH] [DWARFLinker] Release input DWARF after object has been
 linked (#68376)

dsymutil is using an excessive amount of memory because it's holding on
to the DWARF Context, even after it's done processing the corresponding
object file. This patch releases the input DWARF after cloning, at which
point it is no longer needed. This has always been the intended
behavior, though I didn't bisect to figure out when this regressed.

When linking swift, this reduces peak (dirty) memory usage from 25 to 15
gigabytes.

rdar://111525100
(cherry picked from commit 29a1567435ed56a56410fce76d0dedc89683dc81)
---
 llvm/include/llvm/DWARFLinker/DWARFLinker.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/llvm/include/llvm/DWARFLinker/DWARFLinker.h b/llvm/include/llvm/DWARFLinker/DWARFLinker.h
index 9543546935eef..e573419e59db4 100644
--- a/llvm/include/llvm/DWARFLinker/DWARFLinker.h
+++ b/llvm/include/llvm/DWARFLinker/DWARFLinker.h
@@ -276,6 +276,12 @@ class DWARFFile {
 
   /// Helpful address information(list of valid address ranges, relocations).
   std::unique_ptr<AddressesMap> Addresses;
+
+  /// Unloads object file and corresponding AddressesMap and Dwarf Context.
+  void unload() {
+    Addresses.reset();
+    Dwarf.reset();
+  }
 };
 
 typedef std::map<std::string, std::string> swiftInterfacesMap;
@@ -524,7 +530,8 @@ class DWARFLinker {
     /// the debug object.
     void clear() {
       CompileUnits.clear();
-      File.Addresses->clear();
+      ModuleUnits.clear();
+      File.unload();
     }
   };