Index: lld/docs/ReleaseNotes.rst
===================================================================
--- lld/docs/ReleaseNotes.rst
+++ lld/docs/ReleaseNotes.rst
@@ -29,6 +29,8 @@
 * ``-z pack-relative-relocs`` is now available to support ``DT_RELR`` for glibc 2.36+.
   (`D120701 <https://reviews.llvm.org/D120701>`_)
 * ``--no-fortran-common`` (pre 12.0.0 behavior) is now the default.
+* ``FORCE_LLD_DIAGNOSTICS_CRASH`` environment variable is now available to force LLD to crash.
+  (`D128195 <https://reviews.llvm.org/D128195>`_)
 
 Breaking changes
 ----------------
Index: lld/test/ELF/crash-report.test
===================================================================
--- /dev/null
+++ lld/test/ELF/crash-report.test
@@ -0,0 +1,11 @@
+# REQUIRES: backtrace
+
+## Test the diagnostics produced when LLD crashes.
+
+## Unset LLD_IN_TEST as it engages a crash recovery context.
+# RUN: env -u LLD_IN_TEST FORCE_LLD_DIAGNOSTICS_CRASH=1 not --crash ld.lld -o /dev/null 2>&1 | FileCheck %s
+
+## Check the crash text has the correct structure.
+# CHECK: crashing due to environment variable FORCE_LLD_DIAGNOSTICS_CRASH
+# CHECK: PLEASE submit a bug report to {{.*}} and include the crash backtrace.
+# CHECK: Stack dump:
Index: lld/test/lit.cfg.py
===================================================================
--- lld/test/lit.cfg.py
+++ lld/test/lit.cfg.py
@@ -104,6 +104,9 @@
         config.have_libxml2):
     config.available_features.add('manifest_tool')
 
+if config.enable_backtrace:
+    config.available_features.add('backtrace')
+
 if config.have_libxar:
     config.available_features.add('xar')
 
Index: lld/test/lit.site.cfg.py.in
===================================================================
--- lld/test/lit.site.cfg.py.in
+++ lld/test/lit.site.cfg.py.in
@@ -10,6 +10,7 @@
 config.llvm_shlib_dir = "@SHLIBDIR@"
 config.llvm_shlib_ext = "@SHLIBEXT@"
 config.lit_tools_dir = "@LLVM_LIT_TOOLS_DIR@"
+config.enable_backtrace = @ENABLE_BACKTRACES@
 config.errc_messages = "@LLVM_LIT_ERRC_MESSAGES@"
 config.lld_obj_root = "@LLD_BINARY_DIR@"
 config.lld_libs_dir = lit_config.substitute("@CURRENT_LIBS_DIR@")
Index: lld/tools/lld/lld.cpp
===================================================================
--- lld/tools/lld/lld.cpp
+++ lld/tools/lld/lld.cpp
@@ -214,6 +214,12 @@
   InitLLVM x(argc, argv);
   sys::Process::UseANSIEscapeCodes(true);
 
+  if (::getenv("FORCE_LLD_DIAGNOSTICS_CRASH")) {
+    llvm::errs()
+        << "crashing due to environment variable FORCE_LLD_DIAGNOSTICS_CRASH\n";
+    LLVM_BUILTIN_TRAP;
+  }
+
   // Not running in lit tests, just take the shortest codepath with global
   // exception handling and no memory cleanup on exit.
   if (!inTestVerbosity())