1 files changed, 17 insertions, 0 deletions
diff --git a/llvm/tools/llvm-objcopy/CopyConfig.cpp b/llvm/tools/llvm-objcopy/CopyConfig.cpp
index 94c0a5bc631..0b0023f52d8 100644
--- a/llvm/tools/llvm-objcopy/CopyConfig.cpp
+++ b/llvm/tools/llvm-objcopy/CopyConfig.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Errc.h"
+#include "llvm/Support/JamCRC.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/StringSaver.h"
 #include <memory>
@@ -490,6 +491,22 @@ Expected<DriverConfig> parseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
   }
 
   Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink);
+  // The gnu_debuglink's target is expected to not change or else its CRC would
+  // become invalidated and get rejected. We can avoid recalculating the
+  // checksum for every target file inside an archive by precomputing the CRC
+  // here. This prevents a significant amount of I/O.
+  if (!Config.AddGnuDebugLink.empty()) {
+    auto DebugOrErr = MemoryBuffer::getFile(Config.AddGnuDebugLink);
+    if (!DebugOrErr)
+      return createFileError(Config.AddGnuDebugLink, DebugOrErr.getError());
+    auto Debug = std::move(*DebugOrErr);
+    JamCRC CRC;
+    CRC.update(
+        ArrayRef<char>(Debug->getBuffer().data(), Debug->getBuffer().size()));
+    // The CRC32 value needs to be complemented because the JamCRC doesn't
+    // finalize the CRC32 value.
+    Config.GnuDebugLinkCRC32 = ~CRC.getCRC();
+  }
   Config.BuildIdLinkDir = InputArgs.getLastArgValue(OBJCOPY_build_id_link_dir);
   if (InputArgs.hasArg(OBJCOPY_build_id_link_input))
     Config.BuildIdLinkInput =